Full text of "Occasional papers of the California Academy of Sciences"

See other formats

'^^5-

OCCASIONAL PAPERS

OF THE

California Academy of Sciences

No. 44, 154 pages, 50 figures, frontispiece November 8, 1963

GALAPAGOS ISLANDS

A Unique Area for Scientific Livestigations

A Symposium

presented at the TENTH PACIFIC SCIENCE CONGRESS of the

Pacific Science Association, held at the University of Hawaii,

Honolulu, Hawaii, U.S.A., 21 August to 6 September 1961.

Sponsored by the

National Academy of Sciences,
Bernice Pauahi bishop Museum,

and the

University of Hawaii

Table of Contents

PAGE

Introduction. VICTOR Van Straelen 5

Bathymetry in the Galapagos Region. George Shumway

AND Thomas E. Chase H

The Climate of the Galapagos Islands. Leo Alpert 21

Archaeology in the Galapagos Islands. Thor Heyerdahl . . 45

Opportunities for Botanical Study on the Galapagos

Islands. Henry K. Svenson 53

Biosystematic Studies on Galapagos Tomatoes.

C. M. Rick 59

Composition and Relationship of the Terrestrial Faunas
of Easter, Juan Fernandez, Desventuradas, and
Galapagos Islands. Guillermo Kuschel 79

The Marine Shore-Fishes of the Galapagos Islands.

Richard H. Rosenblatt and Boyd W. Walker 97

Evolutionary Patterns in Danvin's Finches.

Robert I. Bowman 107

Protection and Conservation Problems on the Galapagos

Islands. Misael AcosTA-SOLi's 141

Future Scientific Studies in the Galapagos Islands.

Jean Dorst 147

-3

INTRODUCTION*

Victor Van Straelen

President

Charles Darwin Foundation for the Galapagos Islands

Brussels, Belgium

The Galapagos Archipelago has been termed a "living laboratory of evo-
lution." Today no other oceanic island harbors a greater number of endemic
species of plants and animals than the Galapagos. Once the Hawaiian Islands
had many more. Now most of them are gone— gone with the wind! Such a di-
saster could have been prevented with proper management and without inter-
fering with local economic interests.

To those of us who are concerned with the historical development of
knowledge, and more particularly of the biological sciences, it is striking that
the most momentous turn in man's outlook on life and its forms was based on
observations made in the tropics. From the eastern tropical Pacific area and
some of the islands nearby, Charles Darwin drew his most significant conclu-
sions; from the western Pacific area, in the Malayan Archipelago, Alfred Rus-
sel Wallace came to nearly the same conclusions. The luxuriant plant and an-
imal life of islands located in the oldest of all oceanic areas now existing,
were incentives to answers on what appeared as insoluble enigmas.

Wallace and Darwin became friends and in 1858 published simultaneous-
ly, at a meeting of the Linnean Society of London, their views on what from
thereon was to be known as the theory of descent and the theory of natural
selection. These two great men followed their research in the same directions
although on divergent subjects. Wallace's contribution culminated in a momen-
tous book entitled Island Life.

But in 1859 Darwin published his book "on the origin of species by
means of natural selection, or the preservation of favoured races in the strug-
gle for life." Itisthe result ofhis observations made during a voyage of near-
ly five years on board the Beagle, from the 2nd of December, 1831, until the
29th of October, 1836. Darwin meditated on his observations for more than 20
years before he expressed openly his conclusions about them. He had visited
many islands, among which I shall mention now only the Galapagos.

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U.S.A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-5-

6 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

At a time when nearly all biologists accepted the constancy of species,
Darwin convinced them of the contrary, not by a mere successful compilation
of ideas, but by the presentation of new ideas and a wealth of new facts.
Stirred by his observations on the Galapagos, Darwin collected a vast quan-
tity of evidence and used it for the demonstration of organic evolution brought
about by natural selection. Before that the idea of selection was only known
to breeders who unconsciously practiced what we call today "artificial selec-
tion."

This year (1961) marks the 131st anniversary of the start of this mo-
mentous adventure, and in September, precisely the 127th anniversary of Dar-
win's contact with the Galapagos. He arrived there on the 15th of September,
1835, landing on Chatham Island (San Cristobal). Then on the 23rd on Charles
Island (Floreana), on Albemarle (Isabela) on the 29th, on James (Santiago)
the 8th of October, leaving the Galapagos forever on the 20th of October. His
contact with the fauna of these islands was decisive for the perception of
what would become the theory of descent or evolution. Darwin had an uncon-
tested gift for new observation and for observing new facts by chance. This
was the case with the species of birds he discovered on the Galapagos.

For obvious reasons, Darwin's attention was drawn by the most conspic-
uous elements of the Galapagos fauna: birds and reptiles. It is nearly always
the case, vertebrates and phanerogams easily attract attention. But Darwin,
a birdwatcher from his early boyhood, picked less conspicuous, but most in-
teresting birds from the point of view of evolution, the finches (now known as
Darwin's Finches), recently so masterly studied from an anatomical and ec-
ological point of view by my friend Robert Bowman, Secretary for the Americas
of the Charles Darwin Foundation. I shall dwell no longer on the spectacu-
lar biota of Galapagos.

Surely, by the irresponsible action of man, the flora and the fauna of the
Galapagos are, in many respects, no more what they once were. What remains
of the glorious pieces of architecture and art of ancient Greece and Rome?
Were they not until recent times used as quarries providing building stone for
the housing of barbarian invaders?

But man can destroy beauty which can also be replaced by man, provided
that he has the necessary genius. Never is he able to coin a new form of liv-
ing being. He who takes that responsibility of destruction, even if he has no
sense of doing so, cuts forever a link with a very remote past and an infinite
chain of processes leading to an unforeseeable future.

In Galapagos the native life forms and their associations are in mortal
danger. Surely, we may already be grateful to the Ecuadorian Government for
having responded favorably to the many calls for protection that scientific
bodies have addressed to it for more than thirty years, such as the National
Academy of Sciences of the United States, the Royal Society of London, the
Academiedes Sciences de Paris, die Preussische Akademie des Wissenschaf-

No. 44) VAN STRAELEN: GALAPAGOS SYMPOSIUM 7

ten, Academie royale de Belgique, and so on. UNESCO took on the problem
from the very beginning of its inception as an international organization in the
days when Sir Julian Huxley was its Director-General.

In 1961 the General Assembly of the International Union for Biological
Sciences met at Amsterdam, in the seat of the Dutch Royal Academy of Scien-
ces, and on July 15 voted unanimously a resolution imploring the Ecuadorian
Government to take steps for the rescue of the Galapagos biological treasures.

On the 29th of September, 1961, the Xth Pacific Science Congress as-
sembled at Honolulu voted unanimously a similar motion. Over 2750 scientists,
coming from all areas surrounding the Pacific Ocean and from western Europe,
participated in this action.

But protection and conservation laws as enacted on two occasions for
Galapagos by the Government of Ecuador are very difficult to enforce and they
need understanding. Nature conservation is a technique that comes under ap-
plied biology.

This is the reason, among many others, why, under the sponsorship of
UNESCO, the Charles Darwin Foundation for the Galapagos Isles was created
in 1959, on the occasion of the centennary of the publication of "The Origin
of Species." No more fitting memorial could be erected to Charles Darwin
whose name stands alongside that of Isaac Newton.

By mentioning Isaac Newton, I think of the rapid advances of the physi-
cal sciences during the past 100 years, progress in understanding that far sur-
passes the rate of increase of knowledge in the field of biology. A simple cen-
sus of present living forms is still in its very beginnings. Perhaps no more
than tv^enty-five per cent of lower plants and animals are known. Organisms,
representing high ranking systematic divisions, are still discovered nowadays.
Many organisms living in fresh or marine waters or between the grains of soil
remain to be discovered. The behavior and life conditions, what incur present-
day jargon we call ethology and ecology respectively, are known only approx-
imately for a few vertebrates and insects.

Why is this so? Because many branches of biology did not have the ben-
efit of the strong cooperating organizations that made possible the incredible
developments of physics in its broadest sense. Biologists are still the poor-
est among the members ofthe scientist family. The future generations will be
amazed by the neglect from which we are suffering. Does man not belong to
that largest category among those that can be distinguished on earth and that
are the living beings?.

It is one ofthe aims of the Darwin Foundation to go into a close inves-
tigation of the life communities existing on the Galapagos, provided this or-
ganization obtains the resources needed. A very ambitious plan has been
drawn up which includes many problems in the physical and geophysical sci-
ences. Many years, and still more qualified people drawn from all nations, are

8 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

needed for its realization. Surely, as discoveries are made, the plan will be
broadened. Everything points to the fact that speciation in the Galapagos is
not restricted to vertebrates, but includes all groups of living beings present
on the isles and in the adjoining seas.

Until recently, investigations on the origin of diversification in marine
organisms have been made on a very restricted number ofmollusks and fishes.
There is much evidence that the seas bathing the shores of Galapagos will
provide a most favorable opportunity for tackling these problems. The diver-
sity of the physics of waters due to the confluence of cold and warm currents
is surely at the origin of great differentiations in the environments. Variations
in ecological factors are, evidently, responsible in the long run for morpho-
logical variations, and as we all know, living beings until now, have been de-
fined mainly by their shapes.

Another aspect of investigations on sea-waters has recently been re-
vealed. Up to now sea-water appeared to be a solution of mineral salts. There
is much evidence that besides these salts a fair amount of organic matter is
dissolved in the seas. Saturated and non-saturated hydrocarbons exist. In
most of the waters of the old world this problem cannot safely be investigated
on account of the numerous streams carrying enormous amounts of polluted
waters into the oceans. This complication does not exist around Galapagos
and therefore this region provides an ideal site for future investigations along
this line.

All over the world the bulk of life communities remain unexplored. Be-
low the northern tropics, especially on the American continent, the wealth and
variety of these communities is far greater than in any other part of the world
at the same latitude.

No continent possesses a greater wealth of plant and animal life than
Central and South America. We know that until about a century ago, it was the
same for the Caribbean islands, now covered with a cosmopolitan world of life
that came in and destroyed biological communities as endemic as those of the
Galapagos.

On the South American continent life is far richer than in Africa. The
Congo and Cameroon forests, the only green spots of importance still exist-
ing in Africa, maybe mentioned as poor when they are compared with the Am-
azonian forest in its broadest sense. The potentialities of these renewable
resources are as yet unexplored.

The Galapagos international undertaking cannot bear full fruit unless,
first of all, it is considered by the Ecuadorian nation as its own enterprise.
Without its understanding and its cooperation in earnest, nothing, in the long
run, can be achieved. Besides the endless investigations we ought to con-
sider the conservation techniques that are now well worked out in many coun-
tries.

The release of exotic species must be stopped all over the archipelago

No. 44) VAN STRAELEN: GALAPAGOS SYMPOSIUM 9

and especially in those areas of Galapagos designated as wildlife reserves.
In the latter, the exotics that turned feral must be controlled through exterm-
ination or by removal. Also, the transplantation of native species from one
island to another should be prohibited until the results of studies still to be
done are known.

Any defacement of the protected areas, due to irresponsible yachtsmen
coming from abroad, must be stopped.

I hope that the day will soon come when all our South American states
will establish large natural reserves on their territories following the example
of the Republic of Ecuador.

A heavy responsibility rests on the shoulders of the South American re-
publics with regard to the proper use and maintenance of the wealth of their
territories. They are now confronted with the conservation problems and all
that this means. Let them not follow the distressing examples of so many ter-
ritories of the Old World.

From my early childhood I had contacts with Latin America. It is only
during the last ten years that I have been called upon to participate in certain
scientific undertakings sponsored there by UNESCO. The philosophy of all
the states of this continent is not unfamiliar to me. Expression of high ideals
are easily discovered, even when they are hidden by a passing dark cloud,
whose silver lining reveals the persistence of the source of enlightenment.

Educational systems are an expression of the ideas of nations. Let the
Latin American systems offer some chances for the understanding of nature
and its conservation so as to make the gift of life more valuable and the men
more worthy of the gift.

BATHYMETRY IN THE GALAPAGOS REGION

George Shumway

U. S. Navy Electronics Laboratory
San Diego, California

and
Thomas E. Chase

U. S. Bureau of Commercial Fisheries
Biological Laboratory
San Diego, California

Most of the bathymetric data presented here are from expeditions of
Scripps Institution of Oceanography, based on sounding lines obtained while
crossing the region during the course of other work (fig. 1). Especially use-
ful sounding lines were obtained by Scripps expeditions SHELLBACK, DOL-
PHIN, STEP-I, RISEPAC, and SWAN-SONG. Additional sounding lines have
come from U.S. Navy ships participating inHIJUMP expedition. U.S. Navy Hy-
drographic Office chart 1798 contains a number of isolated soundings in the
vicinity of the islands which also were included. Because available data are
not abundant and sounding information is randomly located, the charts pre-
sented here must be considered only a preliminary synthesis.

On all expeditions of Scripps Institution of Oceanography, echo sound-
ings were obtained with AN/UQ-1 echo sounders and were recorded on Preci-
sion Depth Recorders (except SHELLBACK, made before PDR's were used).
The acoustic soundings were made with the assumption of an average sound
speed in sea water of 4800 ft/sec. Corrections for true water sound speed have
not been made.

The remoteness of the Galapagos Islands from the important world trade
routes and the incomplete status of the mapping of the ocean floors have left
the bathymetry of the Galapagos region relatively unknown up to the present
time. In the past decade sufficient data have accumulated to construct the
charts presented here (figs. 2, 3, 5, 6, 7). A series of charts of the eastern
tropical Pacific including the Galapagos region is being prepared by the U.S.
Bureau of Commercial Fisheries and the Institute of Marine Resources, Uni-
versity of California.

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U. S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

- 11

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

io*>

I00<

95<

90«

85=

80<

75°

Figure 1. Sounding lines in the east equatorial Pacific Ocean, from Scripps Institution
of Oceanography and U. S. Navy cruises.

Regional Setting

The Galapagos Islands are a group of typical Pacific Basin basaltic
volcanoes (MacDonald, 1949) about which there is little petrographic informa-
tion. The volcanoes do not rise directly from the deep sea floor, but are perched
on a platform elevated a thousand fathoms or more above the surrounding deep
sea floor. This platform connects through a saddle on the east with the Car-
negie Ridge (Shumway, 1957), and on the north it joins Cocos Ridge (Shumway,
1954). Typical fracture zone topography (Menard, 1955a, 1955b, 1960; Menard
and Fisher, 1958) extends westward from the vicinity of Darwin Island for
more than a thousand miles.

In the past decade, largely through the efforts of H. W. Menard and R. L.
Fisher of Scripps Institution of Oceanography, an overall picture of the bath-
ymetry in the eastern Pacific Ocean has come to light. It reveals that the dom-
inant topographic features, beyond the trenches at the continental margins.

No. 44)

SHUMWAY & CHASE: GALAPAGOS SYMPOSIUM

CREST OF EAST PACIFIC RISE
(\\\\\1 FRACTURE ZONES
RIDGES

40«

20«

20°

40«

160°

140°

120

Figure 2. Crest of East Pacific Rise and location of East Pacific fracture zones (after
Menard, 1960, modified),

are the East Pacific Rise, which is an elongated bulge of the sea floor ex-
tending from the vicinity of Antarctica to the Gulf of Alaska, and a series of
fracture zones running westward from the continents for distances up to 3000

CALIFORNIA ACADENiY OF SCIENCES

(Occ. Papers

miles (fig. 2) (Menard, 1960). The Galapagos Islands are located on the east-
ern flank of the East Pacific Rise, and the Galapagos fracture zone cuts across
the East Pacific Rise and apparently dies out on the western flank. The fact
that Cocos Ridge meets the trend of the Galapagos fracture at an oblique an-
gle does not seem to be unique, for the Clipperton fracture to the north has
the Tehuantepec Ridge joining it obliquely, and the Easter fracture zone to
the south has the Nasca Ridge joining it obliquely; all three ridges, Cocos,
Tehuantepec, and Nasca have similar northeast-southwest trends. Thus the
fracture zone and ridges associated with the Galapagos Islands are part of a
regular system of topography in the eastern Pacific.

Figure 3. Eastern portion of Galapagos Fracture Zone, showing location of transverse
profiles.

Galapagos Fracture Zone

The existence of fracture zone topography west of Darwin Island was
shown by Shumway (1954) on the basis of two echo sounding lines run across
it by the SHELLBACK expedition; but when his manuscript was written in 1953,
fracture zones had net assumed the importance geologically they now have.
The matter was not pursued further at that time. Menard (1955) mentioned that
on the basis of the limited information then available, a fracture zone running
west from the region of the Galapagos Islands probably existed. By 1960 with
more data available, Menard (1960) included a fracture zone in the vicinity of
the Galapagos Islands on his bathymetric chart of the Pacific Ocean.

The following description of the Galapagos fracture zone is preliminary
and is based upon soundings obtained through 1961. These data consist pri-

No. 44)

SHUMWAY & CHASE: GALAPAGOS SYMPOSIUM

J STEP

_U-

J^J^,

^IkJIk

SWAN SONG

96° W

95° W

•M

!■«

,-.

oooru-

SHELLBACK

IBOO-

y.A-^Vv— ^-— ^^ ^/. \

— 1-

'l/V/"

~-^-\^vyi

lil^ ^

- "

5-H

2-N

I'N

OOFM-

EASTROPIC

I90O-

—

,-A

/\— • — ^

^'^

■

lorw

4'N

3'N

2*N

(•

SHELLBACK

rtfl

1500-

iOOO-

^ — -^—

— ' '[lillll!l!lllllllil

lililliillllllllillllllllllllllliilllllllllll

IllHliliHillilliilii

liliil liJll,!l,lll!llllllllllllllllli

llllllillllll;

■iiiiUll

lorw

GALAPAGOS FRACTURE ZONE

VERT EXAG < 20

Figure 4. Transverse profiles across eastern portion of Galapagos Fracture Zone.

marily of transverse crossings of the zone. Large areas remain to be surveyed
to ascertain the continuity of east-west trending ridges, troughs, and other
structures (figs. 3, 4).

For the sake of explicitness we refer to the zone of irregular topography
running west from Darwin Island as the Galapagos fracture zone, and retain
the established names Cocos Ridge and Carnegie Ridge for the related struc-
tures to the east. This does not imply that the variously named features are
structurally separate entities. Rather, it is probable that these features are
structurally related and that they are part of the fracture zone.

Galapagos Platform

The volcanic islands of the Galapagos are perched on top of a platform
whose top lies a thousand fathoms or more above the deep sea floor to the
south (fig. 5). It does not seem appropriate to call this feature a ridge, for
at the 700 fathom isobath it has a length of 270 sea-miles and a width of about
100 sea-miles, and isobathic contours along its southwestern slope have a
marked convexity.

To the east, the platform connects through a saddle with the western
end of the Carnegie Ridge (figure 6 (Shumway, 1957). The low point of the
saddle lies between 1200 fathoms and 1300 fathoms.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

GALAPAGOS ISLANDS REGION

Figure 5. Bathymetry in the vicinity of Galapagos Islands.

On the south, southwest, and west sides, the Galapagos platform drops
steeply to the deep-sea floor at more than 1800 fathoms depth. On the south-
west side there is an elongate depression about 200 fathoms deeper than the
sea floor farther to the southwest (fig. 5). Similar marginal depressions often
are present around large seamounts, and a notable depression is found along
the eastern and northeastern sides of the Hawaiian Ridge (Hamilton, 1957).
The steep side of the platform lies close to the west and southwest sides of
Fernandina Island and Isabella Island, with depths of 1700 fathoms being
found within 6 or 8 sea-miles of the islands.

On the northeast side of the platform the bottom drops off gradually to-
ward the Panama Basin without complications. On the north and northwest
sides, however, the topography is complex; it is in this region that the frac-
ture zone, Galapagos platform, and Cocos Ridge meet (figs. 3, 5, 7). Unfor-
tunately, not enough sounding data are available to allow the complex topo-
graphy to be resolved in the detail desirable,

A tongue of relatively deep water, i.e. greater than 1400 fathoms, lies
between the north end of Isabella Island, Pinta Island, and Marchena Island.
Darwin Island and Wolf Island are isolated from the Galapagos platform by
about 60 sea-miles of water deeper than 1200 fathoms; in this respect they
are not part of the Galapagos group.

The upper surface of the Galapagos platform contains numerous irregu-
larities that cannot be contoured adequately on the basis of available sound-
ing data. No attempt has been made to depict contours shoaler than 700 fath-

No. 44)

SHUMWAY & CHASE: GALAPAGOS SYMPOSIUM

Figure 6. Bathymetry for Carnegie Ridge and the eastern end of the Galapagos Platform.

oms (fig. 5). A very detailed survey would be necessary to determine the in-
ter-island bathymetry.

Cocos Ridge

Cocos Ridge, running from the vicinity of Costa Rica to the region im-
mediately north of the Galapagos Islands via Cocos Island was discussed by
Shumway (1954). Since then additional sounding data which improve knowl-
edge of the ridge have been obtained (fig. 7). Fisher's (1961) chart of the
Middle America Trench shows that the northern end of Cocos Ridge is termin-
ated by relatively deeper water at the eastern end of the Middle America Trench.
The trench, however, does not extend east of the ridge. These facts suggest
that the two structures have exerted some influence upon each other at their
place of junction.

A favorably directed sounding line, running in an east-west direction at
about 5° N. latitude, was obtained by Scripps Institution of Oceanography ex-
pedition DOLDRUMS. A bathymetric profile drawn from data obtained on this
sounding line (fig. 8) reveals a domed central portion about 100 sea-miles in
width flanked on the west by a steep escarpment about 500 fathoms high. To
the east of the escarpment there is a steep-sided elevation, but apparently this
is a local feature.

The data suggest that the northwest flank of Cocos Ridge may be a zone
of particular crustal instability where repeated volcanic activity has created

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

W> •W* COhw(IKJA<. rijMfA.tS 4 WSkt

COCOS RIDGE

Figure 7. Bathymetry for (^oros Ridge.

a narrow ridge, portions of which rise higher than the main, central part of
cos Island, is located along this northwestern flanking ridge.

Co-

SUMMARY

The Galapagos Islands rise from an elongated platform ofeastwest trend
which at the 700 fathom isobath is 270 sea-miles long and 100 sea-miles wide.
South and west of this platform the sea floor drops steeply to depths greater
than 1800 fathoms. The eastern end of the platform connects through a saddle
with the Carnegie Ridge. On the northeast side of the platform the sea floor

No. 44)

SHUMWAY & CHASE: GALAPAGOS SYMPOSIUM

VERT EXAG X20

Figure 8. Bathymetric profile across Cocos Ridge along an east-west line at 5°N.

drops off gradually toward the Panama Basin. To the north, the platform unites
with the end of Cocos Ridge and with a fracture zone that extends westward
from the vicinity of Darwin Island.

The fracture zone that extends almost due west from Darwin Island con-
tains topographic features typical of the other fracture zones which parallel
it to the north. This distinctive topography, with high narrow ridges adjacent
to deep troughs, extends at least 600 sea-miles west of Darwin Island; the
zone is less well defined farther west, but there is evidence of it as far as
1600 miles west of Darwin Island.

Literature Cited

Fisher, R. L.

1961. Middle America Trench: topography and structure. Geological Society
of America Bulletin, vol. 72, pp. 703-720.

Hamilton, E. L.

1957. Marine geology of the southern Hawaiian Ridge. Geological Society of

America Bulletin, vol. 68, pp. 1011-1026.

MACDONALD, G. A.

1949. Hawaiian petrographic province. Geological Society of America Bulle-
tin, vol. 60, pp. 1541-1596.

Menard, H. W.

1955a. Deformation of the northeastern Pacific Basin and the west coast of
North America. Geological Society of America Bullet in, vol. 66, pp.
1149-1198.

Menard, H. W., and R. L. Fisher

1958. Clipperton Fracture Zone in the northeastern equatorial Pacific. Jour-

nal of Geology, vol. 66, pp. 239-253.

SHUMWAY, Geo.

1954. Carnegie Ridge and Cocos Ridge in the east equatorial Pacific. Jour-
nal of Geology, vol. 62, pp. 573-586.
1957. Carnegie Ridge bathymetry. Deep-Sea Research, vol.4, pp. 250-253.

THE CLIMATE OF THE GALAPAGOS ISLANDS*

Leo Alpert

Tropical and Desert Branch

Earth Sciences Division

Army Research Office, OCRD

Washington, D. C

Introduction

Little information is available about the climate of the Galapagos Is-
lands - and for that matter, about the entire Eastern Tropical Pacific Ocean
Area - because of the scarcity of surface and upper air weather observations.
Prior to World War II, the only weather data available were contained in the
records of a few scientific expeditions that had visited the islands from time
to time, and some sporadic observations of local inhabitants. Since the ex-
peditions spent only a few weeks in any one locality and were primarily inter-
ested in the fauna, flora, and geology of the islands rather than in the climate,
no complete series of weather observations was obtained. In addition, no ser-
ies of winds aloft or radiosonde observations had been made.

The observations made by Wolf (1879, 1892, and 1895) during August to
November, 1875, and May to July, 1878, have been the basis of all previous
analyses of the weather and climate of the islands.

The Galapagos expedition of the California Academy of Sciences spent
one year, September 24, 1905, to September 25, 1906, in the archipelago, vis-
iting each island at least once and some of the larger islands two or more times
at different seasons of the year. Observations and notes concerning meteor-
ological conditions during this period, and also the. botanical regions from
which much valuable information can be inferred (Stewart, 1911), have gone
almost unnoticed, not being utilized by either Knoch (1930) or Schott (1931,
1935, and 1938).

During World War II, an airbase and weather station (0°27'S., 90°6'W.,
10 feet msl) were established on Seymour Island (fig. 1). Seymour Island is
small and "pear shaped," located just north of Santa Cruz Island, and sep-
arated from it by a narrow channel less than one-half mile wide. Seymour is
five miles long and three and one-half miles wide in its widest southern half.

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U. S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-21-

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

9 0'30'
STATIONS-

SEYMOUR

MILES

Figure 1. Topographic map of Seymour Island and Santa Cruz Island,

The volcanic rock surface slopes gradually upward from a sandy beach in the
west to a 200-foot cliff on the windward southeast.

The highest peak on Santa Cruz Island (2,835 ft.) lies 12 miles SSW. of
the former weatherstation on Seymour Island, and is the principal topographic
feature in the immediate station vicinity. This mountain influences consider-
ably the weather and climate of the whole of Santa Cruz Island.

Half-hourly surface observations for aircraft operations were made from
August, 1942, to August, 1945. They included only such elements as pres-
sure, temperature, wind direction and speed, relative humidity, precipitation,
sky condition, cloud type (amount and direction), and weather. No data were
obtained on solar radiation, evaporation, transpiration, soil temperature and
moisture, and dew. In addition to these surface observatioits, some aircraft
observations were made during this period; two to four winds aloft observa-
tions were made daily (Alpert, 1946), and, between February, 1943, and July,
1944, one radiosonde observation was made daily. When, in late 1945, the air-
base on Seymour Island was turned over to Ecuador, the weather station was
closed.

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

The only other series of weather observations of any consequence are
those for the weather station (0° 54' S., 89° 30' W., 20 feet msl) on San Cristo-
bal Island (figure 2). The observations cover the nine-year period, 1950 through
1958, and include only pressure, temperature, weather, precipitation, wind
direction and speed, humidity, cloud type and amount, and storms.

Plans are underway to establish observation stations on Seymour, Isa-
bella, Florena, and Santa Cruz islands. A weather station is being planned for
the Charles Darwin Research Station at Academy Bay on the south coast of
Santa Cruz Island (figure 2). All of these weather stations are located near
sea level and close to shore. No significant series of weather observations
are available for the mountainous interior of any of the islands, where clima-
tic conditions are known to differ considerably from those in the arid lowlands.

Figure 2. Location of weather stations in the Galapagos Islands.

The Dry Season
Along the coast the year is divided climatologically into two distinct

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Figure 3. Patrol aircraft weather reports over the tropical eastern Pacific Ocean, No-
vember 16, 1942. The intertropical convergence zone is shown by the dashed double line. The
station model is outlined in Appendix A. (See Page 42)

seasons, the rainy season lasting from January through April, and the dry
season lasting the remainder of the year.

During the dry season, the intertropical convergence zone is located

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

far north of the islands as shown in the example in figure 3, and exerts no
direct influence on the climate. Divergency in the South Equatorial Current
south of the islands causes upwelling of cold water which is carried past the
southern islands. Figure 4 shows the August ocean surface temperature for
the Eastern Pacific Ocean. A narrow belt of relatively cold water extends in
an east-west direction between 5°S. and the Equator. Ocean surface tempera-
tures increase rapidly north of the Equator. The southerly surface winds (see
figure 3) are cooled in the lower layers by this cold water. Consequently,
abnormally low air temperatures for an island station at sea level in the trop-
ics, are recorded during the months of June through December. Table 1 shows
the climatological data at Seymour Island. The mean daily maximum tempera-
ture is 66° F.

Figure 4. August ocean-surface isotherms for the eastern Pacific Ocean.

The cooling of the lower atmosphere and subsidence in the South Paci-
fic high pressure cell, shown in figure 5, contribute to the formation of a tem-
perature inversion. In August, 1952, (Neiburger, 1958), radiosonde observa-
tions from ships indicated that the height of the base of the inversion was at
600 meters among the southern islands at 1° South latitude, and increased to
a height of 800 meters among the northern islands at the Equator (figure 6).
Figure? shows two soundings; one on 31 March 1943, made during an extend-
ed humid spell (lasting from 29 March to 2 April 1943, table 2) of the rainy
season, and the other on 20 October 1943, during an extreme development of
a temperature inversion in the dry season. Table 3 gives additional informa-

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

tion (relative humidity and mixing ratio) for these two soundings; and table 4
shows the winds aloft observations on these two days. This inversion is read-
ily apparent in the dry season sounding of 20 October 1943, shown by the
dashed line in figure 6. On the average, the inversion base is at 3,000 to 4,000
feet, and the top is at 5,000 to 6,000 feet.

Compared to the rainy season, there is a marked "drying" of the entire
air mass (lower specific humidity) especially immediately about the base of
the inversion, which prevents moisture from diffusing aloft from the surface
layers (table 3). The lifting and convective condensation levels increase in
height and the air mass is stable for ordinary lifting and surface heating pro-
cesses. Thus, convection and the formation of cumulus clouds, typical of the
tropics, are dampened.

Table 1. Clhnatological data at Seymour Island weather station.

An.

Average pressure

1000 mb+ (T

11.8

11.0

10.8

10.9

11.1

12.4

12.6

13.0

12.6

12.5

12.1

Mean Maximum

temperature (2^

Mean maximum

temperature (2^

Prevailing wind

direction (2^

!•:

SSE

Average wind

speed (2^

Average relative

humidity (3_

Total rainfall {X_

0.81

1.39

1.06

0.67

0.01

3.97

Prevailing charac-

ter of rain-

fall (4

RW-I.

Total numberdays

with rainfall (J

Number of days

with thunder-

storms (5^

Percent of time

sky was

overcast \1_

(I- August 1942 - April 1944

(J- August 1942 -

August 194J

)

(2 - August 1942 - February 1945

(5^- January 1943 -

August 194

(3^- January 1943- February 1945

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

Table 2. Daily rciinfctll at Seymour Island weather station in

March and April, 1^4 ^.

Date

Inches

DATE

Inches

March 13,

1943

0.01

Aiiri

1943

0.14

0.01

0.38

29,

0.41

13,

0.12

30,

0.33

23,

0.03

31,

0.11

24,

0.19

0.87

0.86

Stratiform clouds form below the base of the inversion in May (table 1),
and are the typical cloud form from May through December. Low stratiform
clouds are present throughout the day over the ocean, but over the islands,
surface heating causes the clouds to break and dissipate during the afternoon.
Generally, it remains clear over land until sunrise. The stratocumulus clouds
form after sunrise, are most dense in the morning, and break in the afternoon.
Occasionally, they may last throughout the day. The breaking of the strati-
form deck over Seymour Island usually coincides with the shift in surface
wind direction from the SSE. land breeze through W. to the WNW. sea breeze
at the Seymour Island weather station. The sea breeze is especially well de-
veloped because of the relatively large temperature difference between the

Table 3- Radiosonde observations at Seymour Island weather station.

31 March

1943

20 Ociober

194 3

Pres.

Elev.

Temp.

ative

Mixing

Pres.

Elev.

Temp.

iative

Mixing

(Mb)

(Feet)

(°C)

Humidity

Ratio

(Mb)

(Feet)

(°C)

Humidity

Ratio

Code

Percent

(Grams/
Kg)

Code

Percent

(Grams/
Kg)

400

-17

(40-49)

1.0

400

-12

(0-19)

0.8

439

-12

(20-29)

0.8

434

-11

(0-19)

0.6

488

20,000

- 7

(40-49)

2.5

490

20,000

- 4

(0-19)

1.0

521

- 3

(60-69)

3.3

532

(0-19)

1.1

608

(60-69)

6.0

552

(30-39)

2.6

692

(70-79)

7.3

635

(0-19)

1.7

710

10,000

(60-69

7.8

710

10,000

(20-29)

3.0

701

(70-79)

9.2

795

(0-19)

2.6

852

5,000

(70-79)

10.9

852

5,000

(30-39)

5.4

862

(70-79)

11.2

890

(70-79)

10.4

934

(70-79)

17.2

928

(70-79)

10.3

1011

surface

17.2

1011

surface

11.3

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 4. Winds aloft observations at Seymour Island weather station.

Elevation

31 MARCH 1943

20 October 1943

(FEET)

DIRECTION

(360°)

SPEED
(MPH)

DIRECTION

(360°)

SPEED
(MPH)

30,000
25,000

120
140

12
8

20,000
15,000
14,000
12,000

250
70
60
20

1
7
8
8

10,000
9,000
8,000
7,000
6,000

40
60
70
50
80

170
200

5,000
4,000
3,000
2,000
1,000
Surface

100
90
80
80
70

170

7
7
9
5
8
8

250
270
200
180
180
140

cold ocean surface and the heated land surface.

Table 1 shows that because of the stable conditions, drizzle (identi-
fied by the "L" in table 1) rather than the rain shower (identified by the "RW")
is the prevailing rainfall type. Over land, the drizzle generally falls between
daybreak and noon on four to nine days each month, but rarely reduces visi-
bility below 3 miles. The drizzle yields only traces to a hundredth of an inch
of rainfall per month on the lowlands during the dry season. Thus, the low-
lands are dry during these months.

The base of the stratiform clouds is generally between 2,000 to 2,500
feet, and the top 3,000 to 4,000 feet. The mountain slopes, particularly on the
windward southern side from a height of about 800 feet upwards, receive pre-
cipitation in the form of drizzle, fog, mist, and heavy dew. This form of pre-
cipitation, known locally as the "garua, "frequently continues for periods of
several days without a break, and the higher mountain slopes are more or less
continuously enveloped in clouds and fog.

The meteorological elements for two typical dry season days are shown
in table 5. Features to note are the cool range of temperatures; stratocumulus
overcast and drizzle forming in the morning and breaking before noon; the
south-southeast land breeze changing to a west-northwest sea breeze; the

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

relatively high wind speeds throughout the day; the typical stratocumulus and
altocumulus.clouds; the southerly direction from which the stratocumulus clouds
are moving; and the relatively high ceiling and good visibility.

The Rainy Season

The rainy season lasts four months, January through April. By January,
as shown by the surface pressure map of April (figure 5), a major shift in the
general circulation has taken place as the intertropical convergence zone

APRIL

OCTOBER

Figure 5. Mean sea level pressure pattern in April and October.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 5- Two typical dry scasoti days at Seymour Ishnid iveather station.

Airway Vikathkr Report

Seymour Island

16 October 1942

Celling (T
(Hundred Ft.)

Sky Condition (2
(Hundred Ft.)

a
t-
1

c
o

c
c

m
J2

Temperature and
Dew Point CF)

o
<b

-o
a

-a
t

a.
m

-a
c

Remarks (4

Clouds (4

0035

25S

67/59

SSE

2-sc-s

0135

23S

66/58

3-sc-s

0235

S/23S

66/59

SSE

COPS 150S

2-ac-u 3-sc-s

0335

S/20S

66/60

SSE

COPS 1505

2-ac-u 3-sc-s

0435

S/20S

66/60

SSE

COPS 120S

2-ac-u 3-sc-s

0535

ElOO

B/20S

66/60

SSE

COPS

3-ac-u 3-sc-s

0635

E 25

68/60

SSE

COPS

8-sc-s

0735

E 25

70/61

SSE

COPS

10-sc-s

0835

E 25

71/61

COPS

10-sc-s

0935

E 28

72/61

COPS

10-sc-s

1035

E 28

76/61

WNW

COPS BINOVC

10-sc-s

1135

27S

78/61

CTPS

3-sc-s

1235

27S

78/62

WNW

CTPS

2-sc-s

1335

27S

79/62

1-sc-s

1435

27S

76/62

WNW

CTPS

1-sc-s

1535

76/62

WNW

CTPS

F-sc-u

1635

76/62

COPS

F-sc-u

1735

20S

75/62

COPS

1-sc-s

1835

20S

71/62

COPS

1-sc-s

1935

E 22

70/61

SSE'

COPS

10-sc-s

2035

E 22

69/62

SSE

COPS

7-sc-s

2135

228

69/62

COPS

2-sc-s

2235

22S

68/62

SSE

COPS

F-ac-u 2-sc-s

2335

E 25'

68/59

COPS

F-ac-u 7-sc-s

(1, (2 , (3 , (^ - See Table 8.

moves southward to a position a few degrees north of the islands. In figure 8
the intertropical convergence zone is located just north of the islands. The
movement and characteristics of the intertropical convergence zone in the
Eastern Tropical Pacific Ocean Area are little known. Weather observations
from the islands can provide data for the study of this important climatic con-
trol of the Eastern Tropical Pacific Ocean Area.

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

Table 5- Continued

Airway Weather Report

Seymour Island

17 October 1942

c _

--;

o 2

.■^ tL,

C o

3 •"

■? -^

n .;;

4^ C

t~-i

bc 1J

5 1^

^ "

c: o

•-"

.5 "^

^ 2

c/)

a,'

. — ' c

*j 4-t

£ ^

-a

>■ D

nJ V)

^ 5

a,' a;
H Q

Remarks (4^

Clouds (4

0035

i: 25

68/60

SSE

COPS

8-sc-s

0135

E 22

f")

68/60

COPS

10-sc-s

0235

E 22

68/59

SSE

COPS

10-sc-s

0335

E 20

68/60

SSE

COPS

10-sc-s

0435

E 20

68/60

COPS

10-sc-s

0535

E 20

L-

66/61

COPS VSBY 4 S L-

10-sc-s

0635

E 22

68/61

SSE

COPS

10-sc-s

0735

E 22

69/61

SSE

COPS

10-sc-s

0835

E 25

70/61

COPS

10-sc-s

0935

E 27

L-

70/61

COPS

10-sc-s

1035

E 28

73/61

SSE

COPS

10-sc-s

1135

E 26

74/62

WNW

COPS

9-sc-s

1235

E 27

76/62

COPS

7-sc-s

1335

26S

77/63

WNW

CTPS

5-sc-s

1435

26S

76/63

NNW

CTPS

3-sc-s

1535

27S

79/61

SSE

COPS

2-sc-s

1635

22S

75/61

WNW

COPS

5-sc-s

1735

E 25

B20S

73/61

COPS

9-sc-s

1835

E 22

O20S

71/63

SSE

COPS RINOVC

10-sc-s

1935

E 22

70/62

SSE

COPS

9-sc-s

2035

E 22

69/63

SSE

COPS BINOVC

10-sc-s

2135

E 22

69/64

SSE

COPS BINOVC

10-sc-s

2235

E 22

69/64

COPS BINOVC

10-sc-s

2335

E 22

70/61

SSE

COPS BINOVC

10-sc-s

With the southward movement of the intertropical convergence zone to a
mean position of T" to 2°N. latitude in February and March, the mean monthly
pressure (table 1) decreases, reaching a minimum in March. The prevailing
surface wind direction shifts from SSE. to E. The average wind speed decreas-
es to less than 8 mph., and calms become relatively frequent. Aloft the wind
direction is easterly at all levels and the wind speed is the lowest of the year,
averaging about 10 mph. (table 4). The islands are in the "Doldrums."

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

With the shift in surface wind direction, the upwelling of cold water to
the south of the islands ceases, and truly tropical temperature conditions pre-
vail. In March, the warmest month, the mean daily maximum temperature at
Seymour Island is 88° F., and the mean daily minimum is 75° F., quite a change
from the September temperatures. During these months, the dry and almost
barren volcanic rock surface of Seymour Island is strongly heated causing lo-
cal convective currents (figure 9). Dust devils are observed in the afternoon,
some extending to 200-300 feet above the island.

There is a noteworthy difference in the typical sounding for the rainy
season, shown by the solid line, compared to the dry season, shown by the
dashed line in figure 7. Temperature increases in the lower layer. Because
of the heating of the lower layers and the decrease in subsidence from the
outflow of the South Pacific high pressure cell, which has been displaced
southward (figure 5), the inversion present during the previous dry season
months is dissipated (table 3).

Figure 6. The topography (hundreds of meters) of the base of the inversion during the
cruise of the Horizon, June and July, 1952, (Shellback Expedition).

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

Convection now carries moisture aloft above the former (dry-season) in-
version level, and a considerable increase in moisture is recorded at all lev-
els as shown in table 3. The air mass is generally conditionally stable, and
is readily made unstable by a moderate amount of either heating or mechani-
cal lifting (such as is induced by the flow of air against the mountains).

Table 6. Wean monthly rainfall at Seymour Island weather station.

YEAR

JAN.

FEB.

MAR.

APR.

MAY

JUNE

JULY

AUG.

SEP.

OCT.

NOV.

DEC.

ANNUAL

1942

T(l)

1943

0.03

1.40

0.07

0.03

0.04

0.02

3.26

1944

0.29

0.68

2.31

1.13

0.03

4.44

1945

2.10

(1) T =Trace

Cumulus clouds first appear over the mountains in January, and almost
daily during the afternoon in the rainy season, convectionally induced rain
showers and, at times, thunderstorms form over the mountains. Figure 10 shows
a cumulo-nimbus cloud over the mountains on Santa Cruz Island. Table 1
shows an average of one thunderstorm at Seymour Island in February. Heavy
local showers may be recorded on the mountain slopes, which, in the opinion
of the author, may receive more than 50 inches of rainfall annually. As the
showers are carried away from the mountains and their sustaining upslope cur-
rents, they dissipate, frequently before reachingthe leeward coast. Figure 11
shows a rain shower on Santa Cruz Island. When a shower is carried across

Table 7. Mean annual rainfall at San Cristobal weather station,
San Cristobal Island (00° 54' S. 89° 5'^' U', 6 meters).

YEAR

JAN.

FEB.

MAR.

APR.

MAY

JUNE

JULY

AUG.

SEP.

OCT.

NOV.

DEC

ANNUAL

1950

0.0

0.06

0.50

0.0

0.02

0.0

0.04

0.33

0.05

0.19

0.25

1.46

1951

3.94

5.04

1.34

3.24

0.60

0.67

2.97

0.29

0.43

0.27

0.09

0.29

19.23

1952

0.87

0.75

0.06

0.0

1.24

0.05

0.09

0.32

0.12

0.47

0.04

0.55

4.54

1953

7.05

19.17

3.39

18.03

6.67

0.09

0.10

0.50

0.29

0.23

0.24

0.22

56.08

1954

0.37

1.75

3.58

0.0

0.02

0.24

0.21

0.85

0.18

0.20

0.26

6.98

1955

0.33

7.69

3.43

0.47

0.08

0.11

0.26

0.29

0.27

0.18

0.27

0.18

13.58

1956

0.17

4.57

11.46

9.21

0.05

0.25

0.32

0.26

0.17

0.34

0.03

27.22

1957

0.14

10.16

13.62

7.01

1.61

0.25

0.21

0.37

0.18

0.43

0.58

2.95

37.57

1958

1.65

4.41

3.60

0.56

0.05

0.06

0.07

0.05

0.09

0.17

0.14

0.28

11.20

A\'G

1.62

5.96

4.54

4.29

1.16

0.17

0.48

0.26

0.23

0.24

0.23

0.55

19.81

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Seymour Island, rainfall may be recorded at the weather station. These show-
ers on Seymour Island are shortlived, local, and cover a small area. At times,
squalls form over the water during the night and produce a short, light shower
when they move across the islands during the early morning.

Thus, even in the so-called rainy season, the coastal lowlands are light-
ly watered, and are arid. The total rainfall (tables 2 and 4) forthe four months
of the rainy season at Seymour Island (according to the short three-year rec-
ord) averages only 3.93 inches.

The heaviest monthly rainfall recorded at the station was 2.31 inches
in March, 1944. In contrast, 0.07 inches was recorded in March, 1943, and
only a trace was recorded in March, 1945. It is surprising that the heavier
rainfall recorded among the islands in the "EI Niiio" year 1943 (see below).

JOCTOBER

ARCH

600

700

800

900

1000

TEMPERATURE CO

Figure 7. Rainy (31 March 1943) and dry (20 October 1943) season sounding at Seymour
Island weather station.

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

Figure 8, Patrol aircraft weather reports over the tropical eastern Pacific Ocean, March
8, 1943. The intertropical convergence zone is shown by the solid double line. The station
model is outlined in Appendix A. (see Page 42)-

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 8.

Tu'o typical

rainy season

days

at Seymour Island

weather

station.

Airway weather Report

Seymour Island 14

February

1943

in
c

Ceiling (T
(Hundred Ft.)

Sky Condition (2
(Hundred Ft.)

1^
o

I.-

[en)

a
o

c
_o

3
t^

w
O

Temperature and
Dew Point (°F)

n
_o

a:
a
_E

-o

OJ
0)
D.

-a
c

Remarks (4, 5

Clouds (4

0035

E150

80/73

ENE

7-ac-e

0135

E150

79/74

NNE

7-ac-u

0235

E150

79/73

8-ac-u

0335

79/73

150S

5-ac-u

0435

808

78/72

wsw

2-as-u

0535

SOS

78/72

3-as-u

0635

E 80

78/72

8-ac-u

0735

E120

B/30S

78/74

ssw

8-ac-se

1-cu-n

0835

E120

B/30S

81/74

CTPS

6-ac-u

3- cu-n

0935

E120

B/30S

82/74

WNW

CTPS

3-ac-u

3- cu-n

1035

E120

B/30S

84/74

CTPS (1) (4

2-ac-u

4- cu-e

1135

E120

B/30S

83/73

CTPS RW-S

2-ac-u

4-cu-e

1235

E120

B/30S

85/74

NNE

CTPS RW-SE (1)

2-ac-u

4- cu-e

1335

S/30S

86/73

ENE

CTPS RW-S (2) 1-ci-

u 1-ac-u

2- cu-n

1435

E120

B/30S

86/72

CTPS RW-S (2)

6-ac-e

1- cu-e

1535

EllO

O/30S

87/73

BINOVC (1)
VSBY 6 S RW

8-ac-e

2-cu-e

1635

E120

O/30S

86/74

BINOVC (1) RW-S

8-ac-e

2- cu-e

1735

E130

B/30S

85/73

(1) RW-S

6-ac-u

2-cu-e

1835

E130

O/30S

84/72

BINOVC (3)

9-ac-e

1-cu-e

1935

E130

B/30S

83/70

SSE

COPS

6-ac-u

1- cu-s

2035

S/30S

82/71

SSE

COPS 150S

4-ac-e

1-cu-u

2135

S/30S

81/71

SSE

COPS 150S

1-ac-e

1- cu-u

2235

80/71

COPS 160S

4-ac-se

F-cu-u

2335

79/73

SSE

160S

5-as-u

(T E=estimated. "^

(2 0=overcast, B=broken, S=scattered, C=clear. (1) Towering cumulus all quadrants.

(3 Visibility unlimited entire period.

(J BINOVC breaks in overcast

COPS clouds over peaks to south,
CTPS clouds topping peaks to south:
Clouds; number of tenths of the layer, kind,
direction from which the cloud is moving,
(ac ^altocumulus, as =altostratus,
ci=cirus, cu=cumulus,

sc = stratocumulus)

(2) Towering cumulus southwest quadrant.

(3) Towering cumulus north quadrant.

(4) Towering cumulus north semi-circle.

(5) Towering cumulus northwest quadrant.

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

Table 8. Continued.

Airway weather Report

Seymour Island

15 February 1943

1-1

)

Ceiling (T
(Hundred Ft.)

Sky Condition (2
(Hundred Ft.)

Weather and or
Obstruction to Visi(

Temperature and
Dew Point (°F)

c
o

o
u

-□
c

-a
c

Remarks ^, 5

Clouds (4^

0035

ElOO

80/73

10-as-u

0135

-s/

79/72

5-as-u

0235

ElOO

79/73

9-as-u

0335

ElOO

79/73

7-as-u

0435

ElOO

78/73

7-as-u

0535

ElOO

78-73

7-as-u

0635

78/74

SSE

lOOS

5-as-u

0735

E150

B/30S

78/74

ESE

COPS (1)(4

3-ac-u

3-cu-e

0835

E150

O/30S

79/73

SSE

COPS BINOVC (2) 2-ci-u

5-ac-s

3-cu-e

0935

E150

O/30S

81/73

COPS BINOVC (4) 1-ci-u

6-ac-e

3-cu-s

1035

E150

O/30S

84/71

CTPS (4)

6-ac-ne

4-cu-e

1135

E150

O/30S

84/72

ESE

CTPS (4)

6-ac-ne

4-cu-e

1235

E150

O/30S

87/76

lOE

COPS RW-S

6-ac-n

4-cu-e

1335

E150

O/20S

84/75

18E

COPS (3) RW-S

6-ac-n

4-cu-e

1435

E 25

0/B

82/72

ESE

COPS \^) rt«-3

4-as-n

6-cu-e

1535

E 25

0/B

R-

81/74

ESE

COPS (3)

4-as-n

6-sc-e

1635

E120

0/25S

80/73

COPS

6-ac-u

4-sc-e

1735

E120

0/25S

80/73

COPS

6-ac-u

4-sc-e

1835

EllO

O/30S

80/72

BINOVC

9-ac-u

1-sc-e

1935

EllO

79/73

BINOVC

10-ac-e

2035

EllO

79/72

10-ac-e

2135

EllO

79/72

ESE

9-ac-u

2235

E180

79/72

6-ac-e

2335

E180

78/74

ESE

6-ac-e

is not reflected in the rainfall record at the Seymour Island weather station.

A similar pattern of low rainfall, less than 20 inches, is evident in the
raintall records at San Cristobal, shown in table 7.

The rainfall and rainy season are very irregular. Virtually rainless years
are not unknown on the lowlands. The years 1906 (Svenson, 1946), 1930 (Sven-
son, 1946), and 1950 (table 7), were almost rainless. During the nine-year
period, 1950-1958, San Crist6bal (table 7) recorded only 1.46 inches of rain-
fall in 1950. During the four rainy season months of that year, no rainfall was

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Figure 9. Scattered cumulus clouds over Santa Cruz Island (background) on 7 March 1943.
Arid surface of Seymour Island in foreground, Seymour Island airfield and former weather sta-
tion are located south of the bay in center of photograph.

recorded in January, 0.06 inches in February, 0,50 inches in March, and only
a trace of rainfall in April,

In contrast to the virtually rainless years that occur from time to time,
such as 1950 at San Cristobal, unusually heavy rains may fall when the "El
Nino" phenomenon is well developed. This was the case only three years
later at San Cristobal, which recorded 56,8 inches of rainfall in 1954, Of
this rainfall, 19.17 inches fell in February, and 18.3 inches in April. Even
May, usually a dry month, recorded 6.67 inches of rainfall that year. Rainfall
was also heavy at San Cristobal in 1957, amounting to 37.57 inches.

The "El Nino" rainfall is known to have affected the island at least in
1891 (Agassiz, 1892), 1925 (Beebe, 1926), 1929 (Svenson, 1946), 1953 (table
7), and 1957 (table 7). It may have occurred there in other years. For example,
the "El Nino" rainfall has been recorded on the west coast of South America
in 1828, 1845, 1864, 1871, 1877-78, 1891, 1904, 1918, 1925-26, 1929, 1932,
1939, 1941, 1943, 1953, and 1957, The "El Nino" appears to be associated
with a southward displacement of the intertropical convergence zone from its
normal position so that the islands are fully under its influence. The pheno-

No. 44)

ALPERT: GALAPAGOS SYMPOSIUM

men on is little understood, and is worthy of further research, which would be
aided considerably by surface and upper air observations from the islands.
The meteorological elements of two typical rainy season days are shown
on table 8. Noteworthy features of table 8 are the tropical range of tempera-
tures; the rain showers forming at noon to the south over Santa Cruz mountains
figure 11); the relatively low wind speeds; the typical cloudscape of low
cumulus and altocumulus; the easterly direction from which the cumulus clouds
are moving; the relatively high ceiling and good visibility.

Rainfall and Vegetation

Since there are no other places on the islands at which rainfall obser-
vations have been made, the areal distribution of rainfall cannot be mapped
reliably. However, the character of the vegetation on the islands is largely
controlled by the rainfall. Thus, the areal distribution of the vegetation re-
flects the areal rainfall distribution, which in turn is dependent to a great de-
gree upon exposure and elevation. However, there are great differences in the
elevation at which different vegetation regions begin and end on the different
islands, and on the sides of a given island (Stewart, 1911). It seems likely
that the size of the island and the degree of the slope are involved.

Figure 10. Cumulonimbus cloud over the Santa Cruz mountains on 4 March 1943. No rain-
fall was recorded at the Seymour Island weather station on this day.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Four botanical regions, the dry transition, moist, and grassy, can be
recognized above the strand vegetation, which forms a narrow belt along the
shores of the islands in certain places. These botanical regions identify two
rainfall zones, the dry zone and the moist zone.

Figure 11. Rainshower over Santa Cruz Island during the latter part of February, 1943.
Runway of Seymour Island airfield in foreground. No rainfall was recorded at the Seymour Island
weather station on this day.

The Dry Zone

From the dry coast, which receives from five to twenty inches of rain-
fall a year, to the 400-1,000 foot level (and up to 1,500 feet on the north side
of James and Santa Cruz islands), the growth is a dull-grey, sparse and scrub-
by thorn-forest, consisting of scattered dwarf deciduous trees between which
grow coarse grasses, low thorny bushes, and cacti which sometimes attain a
height of thirty feet (figure -9). The dry zone covers the major portion of the
surface of all the islands. Since Harrington, Bindloe, Culpepper, Hood, Tower,
and Wenman islands, as well as Seymour Island, do not attain an elevation of
1,000 feet above sea level, they are arid, and support xerophytic plants typi-
cal of the dry region vegetation.

During the rainy season, the coastal vegetation has a deceptive light-
green appearance from the distance. Closer inspection reveals that only the
terminal twigs and end branches are in leaf; underneath, the woody stems are
as bare as in the dry season.

No. 44) ALPERT: GALAPAGOS SYMPOSIUM 41

The vegetation was green down to the water's edge during the "El
Nino" period of 1891 and 1925. Agassiz (1892), who visited the islands dur-
ing the rainy season months of February through April, 1891, wrote, "This
year quite heavy rains extended to the very level of the sea, a somewhat un-
usual state of things. I could not help contrast the green appearance of the
island, covered as they were by a comparatively thick growth of bushes, shrubs
and trees, with the description given of them by Darwin, who represented them
in the height of the dry season in September, 1835, as the supreme expression
of desolation and barrenness."

The Moist Zone

Between about 1,000 and 3,000 feet above sea level on the mountain
slopes, the flora is more abundant and decidedly mesophytic in character. This
is a result of the heavier rainfall in the rainy season, and the availability of
moisture from drizzle, fog, mist (garua), and dew during the dry season, es-
pecially in the southern (windward) slopes. Here the moist zone is 100-200
feet lower than on the northern (leeward) slopes. Between the dry-region ve-
getation and the moist-region vegetation, a transition region is present being
composed of a mixture of xerophytic plants from the dry region vegetation and
the more hardy of the mesophytic plants from the. moist region.

This moist region vegetation is characterized by forests. Some trees
are two feet in diameter. The undergrowth is often dense and resembles that
of the moist tropics, the rain-forest type being closely approached in places.
During March, 1943, the lower boundary of the moist zone could be clearly
seen by the author on the slopes of Santa Cruz Island because of the darker
green color of the rain forest than of the thorn forest.

Above 1,500 feet in certain places, the forests give way to meadows of
long perennial grasses and ferns. Except on protected places, trees are al-
most entirely lacking. The greater speed of the wind at the higher elevations
combined with a somewhat smaller amount of precipitation is probably the rea-
son for the absence of trees (Stewart, 1911).

The drying power of the wind, and the effect of the wind on the struc-
tural form of the plants is marked in the upper exposed parts of the islands.
In addition, these lie near the tops of the mountains. These are often clear,
while a few hundred feet below, the mountain side may be entirely enveloped
in clouds and fog. The soil at the top of the mountains has been observed to
be dry and dusty, whereas at the same time a little below the top, it was moist,
or even muddy.

Only on Albemarle, San Cristobal, and Santa Cruz islands is a grassy
region well developed.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Conclusions

The available data indicate that the climate of the Galapagos Islands
differs from that of most islands near the Equator. These differences are evi-
dent in the surprisingly low air temperatures, the inversion and associated
stable stratiform cloud and precipitation forms, the prevailing sparse rainfall
of the lowlands, and the side extremes of rainless years and years of abun-
dant rainfall when the "El Nino" phenomenon appears.

Weather observations from the islands could contribute materially to the
understanding of the climate of the tropical Eastern Pacific Ocean Area, and
particularly of the intertropical convergence zone.

Additional series of weather observations, including a more complete
coverage of the climatic elements, are needed in order to present a better
picture of the climate and to analyze the inter-relationship of the climate and
the poorly known biota. Thus, weather observations and climatic studies should
be part of the basic research program of the Charles Darwin Research Station.

Appendix A

Station Model for Synoptic Chart

(The station model used in fig-
ures 3 and 8 is outlined below)

(N) Ch Ht (N)

(N) Cm Ht (N)

TT B

V O DD— n

WW GG

(N) Cl Ht (N)

Fp W

B Flight altitude in hundreds of feet.

Cl Low cloud type, international symbol.

Qvi Middle cloud type, international sym-
bol.

Ch High cloud type, international symbol.

DD Wind direction at flight altitude.

F Wind speed at flight altitude, a half

barb equals a Beaufort Force of one

unit.

Fp Frontal passage: i marked wind
shift; >X marked incident or end of
turbulence; O marked temperature
change (not with altitude); begin-
ning orend of precipitation; change
in cloud forms.

GG Greenwich time of observation.

Hb Height (in hundreds of feet) of base
of low, middle, or high clouds above
sea level.

Hj Height (in hundreds of feet) of top of
low, miiidle, or high clouds above

sea level.

N Amount (in tenths) of low, middle, or

high clouds.

TT Temperature in °C. at flight altitude.

V Visibility at flight altitude, the min-

imumvalues ofthe international code.

WW State of current weather, international
symbols.

W State of past weather, international

symbols.

Note that Hg is reported when the plane
is flown below the cloud deck, and Hy is
reported when the plane is flown above
cloud deck. When Hg is reported and Ht
is not reported, N is entered in place of
Ht; when Ht is reported and Hb is not
reported, N is entered in place of Hb .

No. 44) ALPERT: GALAPAGOS SYMPOSIUM 43

Literature Cited
Agassiz, a.

1892. General sketch ofthe expedition ofthe Albatross from February to May,
1891. Bulletin of the Museum of Comparative Zoology, vol. 23, pp.
1-89.

Alpert, L.

1945. The intertropical convergence zone of the eastern Pacific region (I).

Bulletin of the Americ an Meteorological Society, vol.26, pp. 426-432.
1946a. The intertropical convergence zone of the eastern Pacific region (II).

Bulletin of the American Meteorological Society, vol. 27, pp. 15-29.
1946b. The intertropical convergence zone of the eastern Pacific region (III).

Bulletin of the American Meteorological Society, vol. 27, pp. 62-66.
1946c. Weather over the tropical eastern Pacific Ocean, 7 and 8 March, 1943.

Bulletin of the American Meteorological Society, Vol.27, pp. 384-398.
1946d. Atmospheric cross-sections of the stratus zone of the tropical eastern

Pacific Ocean. Transactions of the American Geophysical Union,

vol. 27, pp. 800-812.

1948. Notes on the areal distribution of annual mean rainfall over the tropi-
cal eastern Pacific Oc e an. Bulletin of the American Meteorological
Society, vol. 29, pp. 38-41.
Beebe, W.

1926. The Arcturus adventure, an account of the New York Zoological Soci-
ety's first oce anographic expedition, xix + 439 pp., New York: G.P.
Putnam's Sons.

Darwin, C

1897. Journal of researches into the natural history and geology of the coun-
tries visited during the voyage of H.M.S. Beagle round the world,
under the command of Capt. FitzRoy, R.N.,x+ 519 pp., New York:
D. Appleton and Company.

Ecuador, Republica del

1945. Boletin Me teorologico , No. 2. Quito: Servicio Meteorologico del Ecuador.

1950. Boletin Meteorologico, No. 3. Quito: Servicio Meteorolo gico d el Ec uador.

1954. Boletin Meteorologico, No. 4. Quito: Servicio Meteorolo gico del Ec uador.

1951. Boletin Meteorologico dela Armada del Ecuador, No. 1. Quito: Servicio

Meteorologic a de la Armada.

1953. Boletin Meteorologico dela Armada del Ecuador, No. 2. Quito: Servicio
Meteorologic a de la Armada.

1955. Boletin Meteorologico dela Armada del Ecuador, No. 3. Quito: Servicio

Meteorologic a de la Armada.

1959. Boletin Meteorologica, No.l. Quito: Direccion General de Me teorologia.

Knoch, K.

1930. Klimakunde von Siidamerika. In Handbuch der Klimatologie, Band 2,
Teil G, pp. 123-125. Berlin:

Neiburger, M.

1944. Research paper No. 19, U.S. Weather Bureau, Washington.

1958. Final report, subtropical Pacific meteorological project. Dept. of Mete-
orology, University of California, Los Angeles.

44 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

POSNER, G. S.

1957. Studies of ichthyology and oceanography off coastal Peru. The Peru
current. Bulletin of the Bingham Oce anographic Collection, vol. 17,
pp. 106-155.

SCHOTT, G.

1931. Der Peru-Strom un seine ndrdlichen Nachbargebiete in normaler und anor-
maler Ausbildung. Annals of Hydrographic and Maritime Meteorology,
vol.59, pp. 161-159, 200-213, 240-253.

1935. Geographie des Indischen und Stillen Ozeane. Hamburg: Deutsche See-
warte.

1938. Klimakunde der Siidse e-Inseln. In Handbuch der Klimatologie, Band 4,
Teil T, pp. 37-40. Berlin:

Stewart, A.

1911. A botanical survey of the Galapagos Islands. Proceedings of the Cali-
fornia Academy of Sciences, ser. 4, vol. 1, pp. 7-288-

SVENSON, H. K.

1946. Vegetation ofthe coast of Ecuador and Peru and its relation to the Gal-
apagos Archipelago. American Journal of Botany, vol. 33, pp. 394-426.

SVERDRUP, H. U.

1942. Oceanography for meteorologists, 246 pp. New York: Prentice-Hall, Inc.

U. S. Hydrographic Office.
1944. Monthly surface temperature charts of the south Pacific Ocean. Hydro-
graphic Office Miscellaneous Publications no. 10,532, Washington.

WOLF, T.

1879a. Apuntes sobreelclima delas Islas Galapagos, segun las observacione s
hechas en los meses de Agosto a Noviembre de 1875. Boletin del
Observatorio Astronomico de Quito, No. 3.

1879b. Ein Besuch der Galap agos-Inseln . Sammlung von Vortragen, vol. 1:
H eidelberg.

1892. Geografia y Geologia del Ecuador. Publicada per orden del Gobierno
de la Republica. Leipzig, pp. 469-493.

1895. Die Galapagos-Inseln. Verhandlungen der Gesellschaft filr Erdkunde,
vol. 22, pp. 246-265.

ARCHAEOLOGY
IN THE GALAPAGOS ISLANDS*

Thor Heyerdahl

Laigueglia, Italy

Archaeological investigations of the Galapagos group have until recent-
ly been neglected on the assumption that the area has been outside the range
of aboriginal craft from either South America or Polynesia. It is noteworthy,
however, that the Galapagos group was considered within the reach of abori-
ginal craft from Peru and Ecuador by observers from the 16th to the 19th cen-
tury who were personally familiar with guara-operated balsa rafts, whereas the
confidence in this remarkably ingenious water vehicle disappeared with the
craft itself at the turn of the present century. Discussions on the possibility
of pre-Spanish visits to the Galapagos have all admittedly been biased by the
writers' attitude toward balsa rafts.

When Miguel Cabello de Balboa and Pedro Sarmiento de Gamboa inde-
pendently recorded the 16th century Inca versions of Inca Tupac Yupanqui's
enduring ocean voyage by balsa rafts to distant islands in the Pacific, they
were both personally familiar with the type of rafts in question, which they
also describe. Although Polynesia was still unknown to Europeans, Bishop
de Berlanga had by then drifted so far out as to discover the Galapagos group,
and Balboa suggested that these were perhaps the islands visited by the Inca's
armada of rafts. Sarmiento de Gamboa, however, who was himself a keen navi-
gator, inquired about the old sailing directions still preserved among some of
the Peruvian raftsmen, and concluded that the inhabited islands known to the
coastal raftsmen and only revisited by Inca Tupac's armada were in the South
Pacific on a line west southwest from Callao and at a distance of about 600
leagues (2,400 miles). He was so confident in this specific position that he
talked the Viceroy into organizing the first Mendana expedition which was ac-
tually sailing straight into the waters immediately surrounding Easter Island
when Mendana, to Gamboa's disgust, altered course and, instead, discovered
other islands further away from Peru, first Melanesia, and, on a subsequent
voyage, Polynesia.

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U.S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-45-

46 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

The remarkable capacity of balsa sailing rafts and the expertness of
their crews in navigation were unanimously praised by the contemporary chron-
iclers, including Saamanos, Xeres, Andagoya, Oviedo, Zarate, Las Casas, Bal-
boa, Gamboa, Inca Garcilasso, Benzoni,and Cobo.

In 1619 the Dutch admiral Spilbergen had his whole fleet atPayta, Peru,
supplied with dried fish from a sailing raft that had been out fishing for two
months in the open ocean between Payta and the Galapagos group. The raft is
illustrated with a native crew navigating with characteristic guarahoards sunk
between the logs fore and aft.

In 1680 the buccaneer Captain Sharp cruised in the local waters, trying
as well to land in the Galapagos. His sailing vessel first followed the coast
towards Peru, but turned into the open ocean off Punta Parina to avoid being
detected by the Spaniards. Out there, where the impact of the Humboldt Cur-
rent strikes out towards the Galapagos, and in the midst of what the buccan-
eers describe as a very stiff off-shore gale, they encountered a merchant bal-
sa raft under sail. Their own pilot advised them not to meddle with its native
crew, "for it was very doubtful whether we should be able to come up with
them or not..." We learn from the same early buccaneer record that these ab-
original balsa rafts sail "excellently well," and that some are so big as to
carry two hundred and fifty packs of meal from the valleys of Peru to Panama
without wetting any of it.

In 1736 two Spanish naval officers, Juan and Ulloa, made the first tech-
nical study of the ingenious guara method which permitted the Indians to steer
their rafts into the open ocean irrespective of the direction of the winds. Ar-
chaeological specimens of guara, dating back to pre-Inca times, are still pre-
served in desert graves from the Chimu area and as far south as Paracas and
lea in south central Peru, and, ethnographically, guara were commonly in use
in northern Peru and Ecuador during Juan and Ulloa's investigations in the
Guayas region. They reported that Ecuadorian balsa rafts, from 75 to 90 feet
long, with entire families onboard, and often a cargo of 20 to 25 tons, resisted
the rapidity of the currents in the open ocean off Puna Island and northern
Peru, and added: "...but the greatest singularity of this floating vehicle is,
that it sails, tacks, and works as well in contrary winds as ships with a keel,
and makes very little leeway. This advantage it derives from another method
of steering than by a rudder; namely, by some boards, three or four yards in
length, and half a yard in breadth, called guaras, which are placed vertically,
both at the head and stern between the main beams, and by thrustingsome of
these deep in the water, and raising others, they bear away, luff up, tack, lay
to, and perform all the other motions of a regular ship. An invention hitherto
unknown to the most intelligent nations of Europe..." (Juan and Ulloa, 1748,
vol. 1, p. 264).

Humboldt, Stevenson, and Paris continue to praise the amazing sailing
abilities and seaworthiness of the balsa rafts surviving in the 19th century.

No. 44) HEYERDAHL: GALAPAGOS SYMPOSIUM 47

and in 1832 Morrell reported seeing them fifty miles from land and able to "beat
to windward like a pilot boat..." Skogman on his world cruise in 1854 reported
that deep sea-going balsa rafts even visited the distant Galapagos group, and
he met them at sea navigating with bipod masts and long guaras sunk between
the logs fore and aft (Skogman, 1854, vol. 1, p. 164).

About the turn of the century the balsa rafts disappeared, and the direct-
ly associated and ingenious technique of guara navigation was ignored and
forgotten. Archaeological guara were common, but often ignorantly labeled as
agricultural tools, while writers who have realized it was a former naviga-
tional device have judged the guara to be a kind of rudder or a usual center-
board serving merely as a substitute to a keel to reduce the leeway of a raft.

At this time the first scholarly discussions of possible pre-Spanish vis-
its to the Galapagos began. Historians of Inca history from Markham in 1907
to Means in 1942 have been so impressed by the obviously historic aspect of
Inca Tupac's ocean voyage that they believed his raft armada to have visited
the Galapagos, since these were the nearest oceanic islands. Hutchinson
(1875) had by then termed the balsa raft a "floating bundle of corkwood,"
and Means, although believing the Inca had reached the Galapagos, underesti-
mated the raft which had taken him there, stating it was "obviously a type of
boat that would awake nothing but scorn in the breasts of shipbuilders of al-
most any other maritime people in the world.

Lothrop (1932) made a more comprehensive study of the practical as-
pects of such a voyage, but was misled by an erroneous 19th century source
to believe that the Galapagos could never have been reached by balsa rafts.
He referred to Byam (1850), an English traveller a century ago, who also saw
a balsa beating against the wind off northern Peru, and who was told by his
captain that these rafts could tack much closer into a contrary wind than a
European whale-boat, but that they went slower through the water, and that in
a few weeks they lost their buoyancy and had to be taken ashore to dry. From
the latter statement Lothrop concluded that a balsa raft was unable to remain
afloat at sea long enough to complete a voyage to the Galapagos, and he sug-
gested that Tupac may rather have transported an army by sea and plundered
the mainland to the north of Guayaquil.

Hornell(1946) wrote: "Certainly no ordinary, untreated balsa raft could
make a prolonged oversea voyage unless the Inca's seamen knew of an effec-
tive method of treating its absorbent logs with some kind of waterproofing
composition..." He found it likely, however, that the early Peruvians used some
preparation of gum, resin or wax in some solvent to rub over the logs, and
that this had helped the Inca rafts remain afloat to the Galapagos.

However, the erroneous verdict of the balsa rafts had now spread into
the general Pacific literature, and deprived archaeologists of any stimulus to
investigate the arid and uninhabited Galapagos. General visitors to the group,
rather than being alerted to the possibility of finding pre-Inca vestiges, denied

48 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

it absolutely. For example, vonHagen (1949, p. 178) was lead to assert: "What-
ever islands the Inca sailed to, he did not sail to the Galapagos." He backed
this assertion by citing presumably authoritative statements to the effect that
the Andean seaboard dwellers were "majestically inept" in marine matters,
and concluded that Inca landings in the Galapagos "was a manifest impossi-
bility."

Subsequent events have shown that the modern verdict on balsa rafts
has been erroneous and directly misleading. Since 1947, five manned sailing
rafts from Peru have passed the Galapagos, one to be picked up later drifting
about in the doldrums, and four to end up in East, Central, and West Polynesia.
One was actually heading on for Melanesia when picked up off Samoa. Of more
importance still, renewed experiments with the guara technique carried out by
Estrada, Reed, Skjolsvold, and the writer in a balsa raft off Ecuador in 1953,
resulted in the rediscovery of the functional system of this exceedingly in-
genous navigational invention, verifying all the discredited early records to
the effect that, through a correct interplay between guara fore and aft, the bal-
sa will turn around and tack along any chosen course regardless of wind direc-
tion. Other experiments have shown that balsa rafts of green timber will re-
tain perfect buoyancy for two years and probably more.

Accordingly, the Galapagos are located far within the feasible range
of aboriginal Peruvian and Ecuadorian navigation.

With this knowledge in mind, an expedition organized to search for pos-
sible archaeological sites was led to the Galapagos by the writer in 1953,
with E. K. Reed and A. Skjolsvold as participating archaeologists. No attempt
was made to accomplish an exhaustive survey of the group or any single is-
land, and areas for investigation were selected according to apparent geo-
graphical possibilities for aboriginal occupation combined with primitive land-
ing facilities.

Four pre-Spanish occupation areas were located on three different is-
lands. The largest site was on the plateau above James Bay on Santiago Is-
land, where eight different aboriginal camp sites were located. A mountain
ridge separated these from another site at Buccaneer Bay on the same island.
The two other sites were encountered respectively at Whale Bay on Santa Cruz
and at Black Beach on Floreana. An additional prehistoric site was located
at Cabo Colorado on Santa Cruz by Mr. J. C. Couffer and Mr. C. Hall subse-
quent to the departure of our expedition.

The combined sites yielded in all 1961 aboriginal ceramic sherds, re-
presenting at least 131 pols, probably more. Of these, 44 pots were identifi-
able with known ceramic wares from the coasts of Ecuador and northern Peru
and 13 additional pots are probably identifiable with ware from the same area.
The remaining 74 pots represent aboriginal ware of which 67 are unidentified
merely because of insufficient characteristics in the limited material preserved,
whereas 7 pots are unidentifiable in spite of striking characteristics in the

No. 44) HEYERDAHL: GALAPAGOS SYMPOSIUM 49

remaining sherds. Some sites produced only Peruvian sherds, while others
yielded both Peruvian and Ecuadorian material. The ceramic types from the
North Coast of Peru were studied and identified by C. Evans and B. J. Meggers
of the Smithsonian Institution.

La Plata Molded ware is represented by 3 pots from two different local-
ities in James Bay. San Juan Molded is represented by one pot from another
locality in James Bay. Queneto Polished Plain is represented by 2 pots from
two different localities in James Bay. Tiahuanacoid ware is represented by 3
pots from two different localities in James Bay. San Nicolas Molded is repre-
sented by one pot from James Bay. Tomaval Plain is represented by at least
15 pots from James Bay, Buccaneer Bay, Whale Bay, and Black Beach. Another
five pots from three sites were probable Tomaval Plain. Castillo Plain is re-
presented by at least 10 pots from James Bay, Whale Bay, and Black Beach.
The latter site also produced a Mochica-type clay whistle. Another 6 pots
were probable Castillo Plain. The other identifiable pots were characteristic
plainware of the Guayas area in Ecuador. The material is reported in detail
by Skjolsvold and the writer in Memoir no. 12 of the Society for American
Archaeology.

With the exception of three pots of hitherto unknown non-European type,
represented by 377 rim, handle, and body sherds of a very thin ware with thick,
glossy red slip and complex form, no distinctly new types of ceramic were en-
countered. In other words, the material collected, as such is in itself of scant
scientific value. Its only importance is embodied in the fact that it has been
left behind in the Galapagos Islands, from 600 to 1,000 miles from its identi-
fiable mainland points of origins.

Naturally then, the question arises: to what extent may some of these
remains have found their way to these oceanic islands in post-Columbian times?
It may be useful therefore to review very briefly the early history of the Ga-
lapagos.

The group was accidentally discovered by Europeans in 1535, when
Bishop Tomas de Berlanga was caught by the strong off-shore set of the com-
bined El Nino and Humboldt Current while sailing from Panama bound for Peru.
A day was spent on one island and two on another in futile search of water,
whereupon the Spaniards barely managed to tack hstck to Ecuador against the
strong westbound currents. Coming from Panama, however, the Bishop and
his party could hardly have brought aboriginal Peruvian or Ecuadorian ceram-
ics to the Galapagos.

A second visit to the group occurred in 1546, when Captain Diego de
Rivadeneira stole a ship at Arica, present Chile, and set sail for Guatemala.
He rediscovered the Galapagos, and a brief and futile search for water was
made on one of the smaller islands, whereupon the ship immediately left the
group without setting foot ashore on any of the other islands. Under these cir-
cumstances this party could not have left the sherds under discussion.

50 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

We know that some extremely few other Spanish caravels sailed into the
Galapagos Sea in the latter part of the 16th century, but it is also known that
they made no use of the islands, which they found to be desert and without
fruit or water. It is possible that some of these caravels carried some Indians
on board, and that some of the latter went ashore with ceramic pots, some of
which were broken there, but it is hardly possible that they carried a minimum
of 131 aboriginal pots ashore, and broke them all. Nor would they even have
brought along such variety of ware, representing widely separated geographi-
cal regions and cultural epochs in aboriginal Peru and Ecuador.

Although first referred to as Galapagos on a map by Ortelius in 1570,
this remote group in the treacherous Humboldt Current remained Las Islas En-
cantadas to the Spaniards, until the British buccaneers found it a convenient
hide-out towards the end of the 17th century. As cited above, the buccaneer
Captain Sharp, who described merchant balsa rafts carrying cargo between the
valleys of Peru and Panama, attempted to call at the Galapagos in 1680, but
the currents prevented him even from landing. Four years later, in 1684, Euro-
peans got a brief foothold ashore for the first time, when a group including
Cowley, Dampier, Davis, Wafer, Ringrose, and John Cook anchored for twelve
days in James Bay on Santiago, while dividing their spoils. A British Museum
manuscript by Cowley reflects the isolation of the group until then: "...wee
sailed away to the Westwards to see if wee could find those Islands called
theGalipoloes, which made the Spaniards Laugh at us telling us that they were
inchanted Islands and that there was never any but Captaino Porialto that
had ever seen them but could not come nearethem to Anchor at them, and they
were but Shadowes and noe reall Islands."

A curious incident is that this buccaneer party in 1684 stored a strange
booty in James Bay, including eight tons of quince marmalade. The Viceroy
of Peru detected their hide-out, all the large jars were destroyed, and count-
less sherds of thick, wheel-made "Spanish jars," first noted by Colnett in
1798, are still found all over the local plateau. An interesting point is that
some of these sherds were seen by us imbedded in the large black lava flow
part of which covers a main portion of the local valley, thus showing that this
major volcanic outburst on Santiago Island post-dates A.D. 1684.

These pioneering British buccaneers were followed in 1700 by a French
expedition under Beauchesne-Gouin which remained a month, whereas the Span-
iards arrived to explore and map the group under Torres in 1789, a visit which
is recorded to be the first of any consequence by a Spaniard since Berlanga's
brief visit of discovery.

There is, accordingly, no foundation for a hypothesis of post-European
introduction of the aboriginal refuse in various sites in the Galapagos group.
The identification by Evans and Meggers of the Peruvian ware shows that the
local deposits consist of material dating back through Estero, La Plata, and
Tomaval periods on the mainland, which means that refuse from at least two

No. 44) HEYERDAHL: GALAPAGOS SYMPOSIUM 51

of the Galapagos sited are dateable to Coastal Tiahuanaco times.

The discovery of sherds from a minimum of 131 aboriginal pots broken
and left behind in the Galapagos implies a considerable human activity in
precolonial times. It is quite obvious that our cursory survey failed to encoun-
ter all sites, and only uncovered part of the material still available. Owing to
the general scarcity of soil on the coastal cliffs, much of the refuse is also
washed into the sea. It is also clear that we are dealing with repeated visits
rather than permanent habitation, as the latter would have left thicker depos-
its and a more homogenous ware. A local development would scarcely have
succeeded in achieving an independent evolution in pottery that closely fol-
lowed the mainland pattern from Castillo and Tomaval Plain ware through poly-
chrome Tiahuanacoid, San Nicolas Molded, and finally the three characteris-
tic types of Chimu blackware as represented by Queneto Polished Plain and
San Juan and La Plata Molded. The refuse deposited represents ceramic types
from the Guayas area of Ecuador down to the Casma Valley near the transition
to the Central Coast of Peru, 1,000 miles away.

To summarize: The use of the Galapagos Islands probably as a fishing
outpost is not a practice of European origin, but the continuation of an abor-
iginal pattern that appears to date at least as far back as the Coastal Tia-
huanaco period in the Peruvian archaeological sequence.

Literature Cited
Byam, G.

1850. Wanderings in some of the western republics of America... London.

HAGEN, V.W., VON

1949. Ecuador and the Galapagos Islands. University of Oklahoma Press,
IX + 290 pp.

HORNELL, J.

1946. How did the sweet potato reach Oceania? Journal of Linnaean Society
of London, vol. 53, no. 348, pp. 41-62, figs. 1-2, 1 map. London.

Hutchinson, T. J.

1875. Anthropology of prehistoric Peru. Journal of the Royal Anthropological
Institute, vol. 4. London.

Juan, G., and A. De Ulloa

1748. Relacion historica del viaje a la America Meridional... Vol. 1. Madrid.

LOTHROP, S. K.

1932. Aboriginal navigation off the West Coast of South America. Royal An-
thropological Institute, vol. 62,. London

Skogman, C.

1854. F reg at ten Eugenics Resa Omkring Jorden Aren 1851-53. Vol. 1 . Stockholm.

OPPORTUNITIES FOR BOTANICAL STUDY
ON THE GALAPAGOS ISLANDS* i

Henry K. Svenson

U. S. Geological Survey
Washington, D. C

Establishment of a permanent biological station on the Galapagos Is-
lands offers botanists an unusual opportunity for study of the ecology and
systematics of flowering plants and lichens. Only a small part of the Galapa-
gos Islands has been well explored. The flowering plants are known only in a
provisional way. The lichens, worked on byLinder (1934), are present in pro-
fusion but are comparatively little known, although as "orchilla moss" they
were once used in dyes, and represented the only vegetable product of the Is-
lands that was of any commerical value. The general ecology of the Islands
has been treated in some detail by Stewart (1915), but the ecology of varia-
tion within individual species is almost unknown.

Much of the southern part of Indefatigable Island is accessible by foot
from the Darwin Research Station. Even in the neighborhood of the Station the
complex variability within individual species would be sufficient for the solu-
tion of many fundamental problems that have been known since the time of
Darwin. For example, careful field examination with a hand lens would allow
differentiation of the various species of Cordia (Boraginaceae), the identifi-
cation of which was based by Johnston (1935) primarily on the presence of
simple, branched, or stellate hairs. Likewise, field examination of mature
seeds or achenes of such genera as Altemanthera and Scalesia would further
the understanding of fruiting parts in these difficult genera. It is to be hoped
that plants can be experimentally grown from seeds, in order to solve many of
the tangles associated with variable species in the Galapagos Islands. Such
experiments could be carried on in Hawaii, California, or even in a little plot
adjacent to the laboratory.

Variability within individual species on the Galapagos Islands is more
marked than in the same species on the mainland of Ecuador (Svenson, 1946,

• Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U. S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi bishop Museum, and the University of Hawaii.

1 Publication authorized by the Director of the U. S. Geological Survey.

-53-

54 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

p. 142). The variability commonly takes the form of reduction in leaf surface,
as may be seen in Croton (Svenson, 1935, plate 4), or the lack of spines in
Acanthospermum microcarpum (Robinson, 1902, plate 1), or of leaves and car-
pels as in Sidaspinosa. This variability within species is fundamental to the
study of evolution of species in the Galapagos Islands, and probably uncon-
sciously impressed itself on Darwin. Although Darwin had no extensive knowl-
edge of South American plants and depended upon his friend. Hooker, for ident-
ification of specimens, he was an admirable collector. He saw the great dif-
ference in the vegetation of the Islands compared with what he had seen on
the Peruvian coast. Excellent accounts are given in the Voyage of the Beagle,
and references in the Origin of Species. 2 The letter which he wrote from the
Galapagos Islands to his sister is unfortunately missing (Barlow, 1946). As
an incentive to exploration it may be mentioned that Darwin collected a num-
ber of species in the Islands, including small Compositae such as Elvira in-
elegans, which have never been found again.

Lack (1947) published a memorable account of Darwin's finches, the
only group of birds outstanding as an example of adaptive radiation. As the
diet of many of these birds is vegetative, the identification of seeds in bird
crops should be one of the goals of field study in the Islands [See Bowman,
1961]. Lack states (page 17) that "Most species of Darwin's finches occur on
a number of islands. In some cases the island populations differ sufficiently
to justify division into subspecies, in other cases the differences are less
marked, and yet in others, they are barely perceptible. They are not in general
confined to individual islands." He notes that populations of finches on the
smallest islands, such as Wenman and Tower, are the least variable; that those
on the moderately small islands of Abingdon and Bindloe are somewhat more
variable; and that the population on the larger island of James is more vari-
able still. Whether such generalizations are true of plants is not known. The
relatively small number of species of plants on the Galapagos Islands should
make studies much easier than on the mainland, with its more complicated flora.

Lack notes (page 115) that Darwin's realization that a species may be
represented by different forms in different regions was one of the most impor-
tant results of the voyage of the Beagle, since it led directly to the question-
ing of the immutability of species. He states (page 125), "The apparent fixity
of species is most striking and provides the basis for systematic zoology...
Charles Darwin and many after him are wrong when they assert that the deter-
mination of species is purely arbitrary." Dobzhansky (1941, page 365), simi-
larly finds that, "The notion, entertained by some biologists unfamiliar with

2 In this footnote I extend my appreciation to the late Professor L. J. Henderson of Harvard
University. His course on the history of science introduced me to the Origin of Species, Merz'
History of European Thought in the Nineteenth Century, and his own book, The Fitness of the
Environment, a background for Darwinian evolution.

No. 44) SVENSON: GALAPAGOS SYMPOSIUM 55

the subject, that species are arbitrary units like all other systematic units,
is unfounded." Zimmermann (1954, page 195) observes that Linnaeus passes
in general as the representative of constancy in species from the beginning,
and of an artificial system, but that is correct only of the younger Linnaeus.

We may now turn our attention to a correlation between the vegetation
of the Galapagos Islands, the South American mainland, and the Caribbean re-
gion, and the means by which plants may have come to the Islands. Many Com-
positae are tree-like on islands, but such a point of view can easily be over-
emphasized. Compositae (Baccharis) and also cacti (Cereus) are just as large,
if not larger, on the adjacent mainland of Ecuador. The Galapagos Islands, it
is true, are a focal point of dry zones from the Caribbean to Peru. But between
these dry zones intrudes the great tropical rain forest, which extends from
Darien to Ecuador, with species that have little or no relationship to the Ga-
lapagos flora. Overlooking of this simple fact is, I believe, the basis of much
of Croizat's troubles (1958) in respect to the Galapagos vegetation. Species
on the Galapagos Islands are more variable than those on the adjacent conti-
nent, and Howell (1934, page 515) has fittingly called the Islands "Evolution's
workshop and showcase." The number of species in the Islands is relatively
small, which is all to the good, for more attention can then be paid to varia-
tion in species, without being overwhelmed by their number. It does not mean
that new species will not be discovered in the Galapagos Islands, for every
expedition finds them. The studies should try to show how continental spe-
cies have reached the Islands, in the manner of the excellent contribution
made by Howard (1950) for Bimini Island in the Bahamas.

As adequate meteorological observations are made on the Islands, there
is the opportunity of correlating the climatic area occupied by individual spe-
cies with the distribution of the same species on the mainland. For example,
the yellow-flowered Piscidia carthagenensis Jacquin is one of the largest
trees on the Islands. It was long considered to be the same as the widespread
P. erythrina. Stewart knew it from Chatham and Santa Cruz Islands. Altitudi-
nal distribution of this tree (Svenson, 1935, page 210) exceeds that of any
other tree in the Islands, extending from near the coast at Academy Bay to
over 2,000 feet elevation. Its greatest size is in the most humid region; above
1,000 feet elevation it is dwarfed. On the mainland, Piscidia carthagenensis
is known only from western Ecuador, the Cartagena-Barranquilla region of
Colombia, and the north coast of Venezuela. All of these areas have a dry
climate. Thus the continental distribution of this tree demonstrates that even
the moistest parts of the Galapagos Islands correspond in their vegetation to
areas of dry climate on the mainland. Such continental areas in northern South
America are shown on a map by Sorge (1930). From a general point of view,
the climatic references in respect to vegetation given by Koppen (1931), Lauer
(1951 and 1952), Tregurtha (1961), and especially Papadakis (1961), should
also be consulted.

56 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

The best knov/n example of radiative adaptation of plants in the Gala-
pagos Islands is Scalesia. Sixteen species are recognized by Howell (1941).
The genus is related to Helianthus of western South America, but the exact
relationship is not known. Also of extraordinary interest from the point of
adaptive radiation is the genus Euphorbia, which was elaborated by A. Hass-
ler (1929). All Galapagos species of Euphorbia are related to one another ex-
cept E. viminea, which is known also from the Bahama Islands, and chiefly
from Turks Island. Euphorbia viminea may thus be presumed to have come
from the Bahamas. Nevertheless, the shrub is now common throughout the Ga-
lapagos Islands, and it was treated by Robinson and Greenman (1895, page
136) as an example of unusual variation, with the notation, "Perhaps no spe-
cies to be found on the different islands better illustrates the noteworthy ra-
cial divergence in related forms than Euphorbia viminea." It was first collec-
ted by Macrae in 1825 on Albemarle Island. The variation is, I think, mainly
the difference between adult and juvenile foliage (Svenson, 1935, plate 2).
This species is probably easily spread by proliferations developed in the leaf
axils, and presumably has come from the Bahamas in connection with the salt
and whaling industry. Turks Island was an important source of high-grade
salt for eastern United States during the first half of the nineteenth century,
especially for preservation of meat; and in early days, the salt was loaded
directly into ships by means of wheelbarrows. My friend, Robert Cushman
Murphy has informed me that he does not know of any definite records of
whalers stopping at Turks Island for salt, but there is no reason to suppose
that they did not do so. To show how easily plant fragments can spread, we
may note the peculiar distribution of Eleocharis pachycarpa, a Chilean spe-
cies which appeared at Port Jackson in Australia at a very early date. The
well known anthropologist Herbert Spinden, then of the Brooklyn Museum, sug-
gested a possible explanation to me. In order to avoid the hot journey around
the Cape of Good Hope, ships transported sheep and cattle from England to
Australia by way of Cape Horn, with stops at Buenos Aires and Santiago for
pasture. Under such conditions, fragments of the Eleocharis could easily be
picked up.

In the Galapagos Islands, modern scientific investigation begins with
the visit of David Douglas and John Scouler in January, 1825, but whaling op-
erations were carried on at an earlier date. Woodes Rogers and other pirates
were there as early as 1708. What plant introductions, if any, these early vis-
itors made upon the arid shores of the Galapagos Islands is unknown.

Dry areas of the Islands seem to have the more pronounced endemism.
Darwin found the Galapagos finches to be characteristic of arid regions, and
Howell mentions pockets in arid regions where endemism. is exceptionally well
developed. Thus Howell (1941, page 237) states, "Not uncommonly the same
ecologic factors affecting segregation are locally active in several, unrelated
groups of plants, and because of the peculiar geologic history or critical geo-

No. 44) SVENSON: GALAPAGOS SYMPOSIUM 57

graphic position of the particular district where they grow, an endemic area
may emerge in which unrelated entities exhibit parallel responses to some
specialized ecologic condition. Such an area seems to occur in the vicinity of
Sullivan Bay on James Island where several remarkable and distinct species
are found... another is that region including the Seymour Islands and adjacent
Indefatigable."

Stebbins (1952, page 34), in a general discussion of aridity as a stimu-
lus to evolution, not specifically on the Galapagos Islands, mentions that,
"In the dryer areas it is possible that more species originate, reach their cli-
max, decline, and become extinct, than in more favorable regions. Reduction
of leaf surface, development oftrichomes, scales and other coverings, ofsunk-
en stomata, of deciduous leaves, of extensive root systems, of bulbs, storage
roots, and other structures... all of these appear as frequent modifications of
xerophytes." Many references have been made to the lack of certain families
of plants in the Galapagos Islands, but to me the absence of the Capparida-
ceae, so prominently represented as bushes and trees on the xerophytic coasts
of Ecuador and Peru, is the most striking.

From the foregoing review, opportunities for botanical research in the
Galapagos Islands would appear to be outstanding. For much of the background,
and for help in what I have said, I am especially indebted to John Thomas
Howell of the California Academy of Sciences.

Literature Cited
BARLOW, Nora, ed.

1946. Charles Darwin and the Voyage of the Beagle, unpublished letters and
notebooks. 279 pp. The Philosophical Library. New York.

Croizat, L.

1958. Panbiogeographie. Vol. 1, 961 pp. The New World. Weldon & Wesley,
Herts, England.

DOBZHANSKY, T.

1941. Genetics and the origin of species. Vol. XVL 364 pp. Columbia Univer-
sity Press, ed. 2.

Hassler, a.

1939. On the limitation of the species within the Euphorbia-group Cheloneae
Doiss. Botaniska Notiser, For., Ar. 1939, pp. 745-748.

Henderson, L. J.

1913. The fitness of the environment. The MacMillan Company. New York.

Howard, R. A.

1950. Vegetation on the Bimini Island group, Bahamas, B.W.I. Ecological
Monographs, vol. 20, pp. 317-349.

Howell, J.T.

1934. Cacti in the Galapagos Islands. Cactus and Succulent Journal, vol. 5,

pp. 515-518, 531-532, figs. 1-9.
1941. The Genus Scalesia. Proceedings of the California Ac ademy of Sciences,

ser. 4, vol. 22, pp. 221-271.

58 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Johnston, I. M.

1935. The Genus Cordia. Journal of the Arnold Arboretum, vol. 16, pp. 174-176.

KOPPEN, W.

1931. Grundriss der Klimakunde, ed. 2. Walter de Gruyter & Co. Berlin.

Lack, D.

1947. Darwin's finches. 208 pp. Cambridge Unitersity Press. Cambridge Eng-
land.

Lauer, W.

1951. Die Zahl der humiden bzw. ariden Monate (Isohygromenen) in Siidamer-

ika u. Afrika. Erdkunde, Band V, Heft 4.

1952. Studien zur Klima und Vegetationskunde der Tropen. Bonner Geograph-

ische Abhandlungen, Heft 9.

LiNDER, D.

1934. Lichens of the Galapagos Islands. The Templeton Crocker Expedition
of the California Academy of Sciences. Proceedings of the Cali-
fornia Academy of Sciences, ser. 4, vol. 21, pp. 211-221.

Merz, J. T.

1903. History of European thought in the Nineteenth Century. London.
PAPADAKIS, J.

1961. Climatic tables for the world. Av. Cordoba 4564, Buenos Aires.

Robinson, B. L.

1902. Flora of the Galapagos Islands. Proceedings of the American Academy
of Arts and Sciences, vol. 38, no. 4, pp. 77-269.

ROBINSON, B. L.,and J. M. Greenman.

1895. On the flora of the Galapagos Islands, as shown by the collection of Dr.
G.Baur. American Journal of Science, ser. 3, vol. 50, pp. 135-149.

SORGE, E.

1930. Die Trockengrenze Slidamerikas. Zeitschrift der Gesellschaft fiir Erd-
kunde zu Berlin, pp. 277-287.

Stebbins, L.

1952. Aridity as a stimulant to plant evolution. American Naturalist, vol. 86,
pp. 33-44.

Stewart, A.

1911. A botanical survey of the Galapagos Islands. Proceedings of the Cali-
fornia Academy of Sciences, ser. 4, vol. 1, pp. 7-288.

1915. Some observations concerning the botanical conditions on the Galapagos
Islands. Proceedings of the Wisconsin Academy of Sciences, vol. 18,
pp. 272-340.

SVENSON, H. K.

1935. Plants of the Astor Expedition (Galapagos and Cocos Islands). Ameri-
can Journal of Botany, vol. 22, pp. 208-277.
1946. Vegetation of the coast of Ecuador and Peru and its relation to the Ga-
lapagos Islands. American Journal of Botany, vol.33, pp. 394-498.
TREGURTHA, G. T.

1961. The earth's problem climates. University of Wisconsin Press.

Zimmermann, a.

1954. Evolution, die Geschichte ihrer Probleme und Erkentnisse. Freiberg.

BIOSYSTEMATIC STUDIES
ON GALAPAGOS TOMATOES* i

Charles M. Rick

University of California
Davis, California

Introduction

The present investigations were undertaken in order to ascertain the
natural relationships of the Galapagos tomatoes. These anomalous members
of the genus Lycopersicon deserve attention for several reasons: (1) Systema-
tic problems. Although the Galapagos tomatoes have been collected frequently
and are therefore well documented in various herbaria of the world, numerous
problems have persisted in their biosystematics. The first specimens were
collected by Darwin in 1835 and many additional collections have been made
by numerous expeditions since that time. Various forms of the Galapagos to-
matoes have been classified into as many as four species and subspecies. Al-
though they have attracted the attention of relatively few systematists, much
disagreement can be found among these few treatments. The taxonomic situa-
tion was reviewed and a regrouping of the material proposed by Rick (1956).
(2) Potential contribution to the genetics and breeding of tomatoes. As a new
source of germ plasm for such studies, the Galapagos tomatoes have already
exceeded expectations. For reasons that will be briefly outlined below, these
accessions prove to be unusually useful in enriching the genetic variation of
cultivated tomatoes. (3) Adaptability to experimental approaches. All acces-
sions so far obtained have proved amenable to culture. Although they do not
thrive well under field conditions in the Central Valley of California, they
survive there and grow luxuriantly in the greenhouse and in the field in other
regions (for example, coastal California). The plants flower and fruit when
grown in small containers, and controlled matings can easily be made. Seed
dormancy posed an obstacle to our first investigations, but this problem was

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U. S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

^ Partial support of this work by grant no. G-10704 of the National Science Foundation and GA
AGR 5547 of the Rockerfeller Foiindation is gratefully acknowledged.

-59-

60 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

eventually solved by the application of special seed treatments (Rick and Bow-
man, 1961). These tomatoes therefore constitute one of the few genera in the
Galapagos biota that can be subjected to a wide range of biosystematic ap-
proaches: the nature of breeding systems, compatibility with other species,
genetic differentiation between races, etc. (4) Relationships to the Galapagos
flora in general. In any such investigations it is naturally hoped that the find-
ings on a specific group might shed light on the larger problems— in this case,
the evolution of the Galapagos flora.

The present study is based on herbarium specimens and on living cul-
tures established from 34 accessions collected by Alf Kastdalen, Zouzou
Coray de Castro, Miguel Castro, Otis Barton, and Robert I. Bowman, and by
the writer during a visit in 1956. The writer is greatly indebted to the afore-
mentioned people for tomato accessions and for assistance in many other re-
spects.

Description of Races

The Galapagos tomatoes are all low, spreading herbs with relatively
diminutive plant parts. Although they can be treated in culture as shortcycle
annuals, most plants encountered in the wild are perennials, continually pro-
ducing new branches from the crown of the plant in the same fashion as most
other wild species of Lycopersicon do in their native habitat. They abound in
the arid, lowest zone of the islands, but have also been encountered occa-
sionally in the middle, forested belt of the larger islands. Phenomenally
drought-resistant, they continue to grow throughout the year, and are often the
only mesophytic plants in leaf during the long dry period of the lowest zone
(figures 1 and 2). All examined collections have twelve pairs of chromosomes,
in common with other species of Lycopersicon.

Although differentiated into many different biotypes, all truly native
forms of the Galapagos tomatoes possess in common at least five morphologi-
cal and physiological traits by which they can be distinguished from all other
known species: (1) Yellow or orange fruit color; (2) Yellow-green foliage co-
lor; (3) Minute seed size; (4) Consistent and severe seed dormancy; (5) Char-
acteristic physiological growth requirements. Although poorly understood, the
latter differ from those of any other tomato species we have cultured.

The same traits were recognized in an earlier survey (Rick, 1956), which
was based on herbarium specimens and living material from only three acces-
sions. One of those collections, LA292, then identified as L. esculentum var.
cerasiforme, has since been demonstrated to have been a cultigen, probably
escaped from a nearby garden. No such form with large (>2cm.) red fruits has
been demonstrated unequivocally to be native to the Galapagos Islands. For
more details concerning the taxonomy and description of races the reader is
referred to Rick (1956).

No. 44)

RICK: GALAPAGOS SYMPOSIUM

..W *'

Figure 1. Single plant of L. esculentum var. minor growing among lava rocks near the
north shore of Jervis Island. Elevation 25 feet. Opuntia myriacantha in background. All other
plants are dead or dormant, characteristic of vegetation in the lowest zone during the dry season.

The commonest biotype is L. esculentum var. minor (L. cheesmanii vat.
minor) hereafter designated var. minor. This form is known from at least six of
the main islands and from many different sites on Albemarle and James islands.
In addition to those characteristics that are constant in all Galapagos toma-
toes, as noted above, this biotype exhibits short internodes, large accrescent
calyx, dense hairiness, and highly dissected leaves. The consistent appear-
ance of these four unique traits and other less tangible ones leaves little
room to doubt the close genetic relationship of all accessions of this type.
These traits are shown in figures 1 to 5 of Rick (1956), and the general as-
pects in the wild are shown in figure 1. Var. minor has always been found at
low elevations, sometimes within 100 feet of, and only several feet in eleva-
tion above, the surf. The widespread distribution and proximity to the strand
of this form hint that marine transport of some kind might have been respon-
sible in part for its present distribution.

The next most common entity is one that has most generally been class-
ified as .a form of L. pimpinellifolium, hereafter designated as Gal. ppn. In
contrast to the two preceding biotypes, it has longer internodes, less divided

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

leaves, more elongate corolla segments, fewer hairs, and smaller, spreading
calyx. It corresponds to Rick's drawings (1956), figures 7 to 10, in all details
except for the absence of pedicel articulation illustrated in the latter. Recent-
ly, field studies have revealed that the monogenically-determined absence of
joint is limited to the Academy Bay region of Indefatigable Island and that
normal articulation prevails throughout most of the range of this type. It has
been found on four of the islands, generally at higher points in the lower zone
than var. minor and occasionally extending to the interior of the islands, as
on Indefatigable. As a race this one is less clearly defined, various constant-
ly breeding deviations have been seen in some of the collections as well as
inter gradations with the following form in a few populations. Its typical habi-
tat is shown in figure 2.

The third main type is the typical form of Lycopersicon cheesmanii, the
type locality for which is the north side of Indefatigable. Collections of liv-
ing material have been obtained from this general area and also from nearby
Seymour Island. In some respects typical L. cheesmanii is intermediate be-
tween the two preceding forms. Its morphological affinities are closer to those

Figure 2. Colony of Galapagos form of L. pimpinellifolium (LA430) growing among the
lava boulders along the volcanic escarpment 1 km. NE of Academy Bay, Indefatigable Island.
Note dormant condition of the trees (Piscidia erythrina) and absence of any other vegetation in
leaf, characteristic of the lowest zone during the dry season.

No. 44) RICK: GALAPAGOS SYMPOSIUM 63

of Gal. ppn., but it resembles var. minor in respect to its shorter internodes.
It is intermediate in respect to density of epidermal hairs. Its foliage is some-
what different than that of the two other forms, being less divided than either
and having lateral segments orbicular in outline. A collection showing some
resemblances to typical L. cheesmani has been collected from Essex Point
on the southwestern extremity of Albemarle. The key morphological features
of this biotype have been illustrated by Luckwill (1943).

Various other biotypes of more limited distribution have also been dis-
covered. In most cases these have been encountered in only one population
or in an otherwise very narrowly restricted region. For the most part they can
be described satisfactorily as combinations of characteristics of the preced-
ing three main biotypes.

Population Structure

The flower parts of Galapagos tomatoes, like those of the cultivated
L. esculentum, are disposed to promote self-pollination. After being shed into
the anther tube, the pollen drifts downward to the stigma, which is situated at
the mouth of the tube or is exserted slightly beyond it. The flowers are small
and arrayed much less conspicuously than those of the highly cross-pollinated
species. No inherent barriers to self-pollination exist; a very high proportion
of the artificially selfed flowers set fruit; and under the insect-free condi-
tions of a screened and fumigated greenhouse fruits are set freely, even with-
out agitation of the flowers.

Advantage was taken of every opportunity in the wild to observe the vi-
sits of insects to flowers of Galapagos tomatoes. Such observations were
made in some twelve native populations, the period of observation varying be-
tween two hours to several days per population. The only insect visits observed
were those to a large colony of Gal. ppn. (LA430) in the vicinity of Academy
Bay in the talus of a volcanic escarpment along the trail to the highlands (fig-
ure 2). Here the only known native Gala'pagos bee, Xylocopa darwinii Cocker-
ell (Hurd, 1958), was observed to make sporadic visits to the tomato flowers.
In contrast, the amount of bee activity in nearby flowering trees of Piscidia
was intense. The bees were unquestionably visiting the tomato flowers for
the purpose of collecting pollen because they displayed the usual vector ac-
tivity in such acts as grasping the anther tube with their legs and vibrating it
rapidly with a high-pitched buzz. In a period of 2 1/2 hours spent in this pop-
ulation, only four bees were seen visiting tomato flowers— an activity of re-
markably lower level than that observed in any tomato species on the adjoin-
ing mainland (Rick, 1950) and far less than that seen in neighboring species
of Piscidia, Momordica, and Cryptocarpus.

It was not surprising therefore to find the genetic structure of most pop-
ulations to be exceedingly uniform. With one exception the plants generally
showed remarkable agreement for such genetically stable characters as flower

64 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

shape, inflorescence structure, fruit color, and anthocyanin pigmentation. In
the population LA430, 75 plants were systematically scored for ten morpho-
logical characters and only two were found to deviate in gross morphology
from a single prevailing phenotype. One plant had a normally developed pedi-
cel articulation, in contrast to the aforementioned jointless (/2) condition, and
another had small seedless fruits, presumably resulting from some type of gen-
etic sterility. Opportunity for similar studies was found in two other popula-
tions of the same biotype within the same general area. Extreme uniformity
was again observed in 19 plants constituting the total of one of these popula-
tions (LA439) found on the cliffs bounding the west side of Academy Bay. In
the third population (LA432), encountered 1 km. east of LA430, 163 plants
were examined and 16 were found to deviate in one of several well defined
traits chiefly of the fruits (figure 3). With the following exception, all the
other wild populations studied showed the same degree of uniformity.

The exceptional population (LA438) was one encountered along the
coast of Albemarle approximately 5 km. southwest of Villamil. This area was

also exceptional for the sympatric existence of both var. minor and Gal. ppn.
Here, one isolated colony of about 20 plants was found to show great varia-
tion between plants in what seemed to be various combinations of the traits
of these two biotypes. Of 13 plants that were examined in detail, five were
typical var. minor, the rest being "hybrid" in respect to the presence of some
Gal. ppn. traits. Among the latter, five different types could be distinguished,
several plants each being found for some of the types. Plants of Gal. ppn.
were found several hundred feet away in lower places.

The distributional map of races (figure 5) suggests that a situation sim-
ilar to that for LA438 might exist on the slopes of the crater of Narborough.
Max. minor and Gal. ppn. coexist there and an intermediate phenotype, closely
approximating typical L. cheesmanii has also been found. Since population
studies have not been made there, the existence of variable populations is un-
certain.

The same remarkable degree of uniformity is characteristic of progenies
grown in culture from single wild plants. In no case, even among offspring
from the variable population on Albemarle, was any genetic variation detect-
able. These populations, mostly of no'more than 20 plants apiece, have been
grown from over 50 parent plants from many populations. The degree of uni-
formity typical of this material is illustrated by seedling cultures in figure 4.
In contrast, the level of variability encountered in single-plant progenies of
other wild tomato species is very much greater. From 20 years' experience in
progeny testing tomato lines, I can state with confidence that the uniformity
of Galapagos tomatoes is matched only by highly inbred lines of the cultivated
L. esculentum.

Another interesting aspect of population structure of the Galapagos to-
matoes is the fixation of various recessive genes. One of the first examples

No. 44)

RICK: GALAPAGOS SYMPOSIUM

Figure 3. Fruit samples from population LA432 of Galapagos form of L. pimpinellifolium
east of Academy Bay, Indefatigable Island. One cluster was taken from each of six different
plants, some showing marked morphological deviations from the normal type. Typical form with
jointless f/^j pedicels in upper right. Deviant with normal pedicel joints in middle left. Deviant
with small fruits at lower left. Deviant with strong anthocyanin pigmentation (atv) in lower right.
(1/2 Reduction)

66 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

is the aforementioned jointless trait, governed by a single recessive gene, /2.
Since the time of the earlier work (Rick, 1956), field studies have shown that
this gene is completely fixed in several populations in the vicinity of Aca-
demy Bay. The yellowish foliage color of many populations of L. pimpinelli-
folium is at least partly due to the presence of the lutescent gene /I. A com-
plete lack of anthocyanin, characteristic of an entire population of Gal. ppn.
near Wreck Bay, Chatham, was ascertained to be determined by ag. Although
opportunity has not been found to investigate all of the encountered variations,
at least one mutant trait encountered segregating within a population has been
found to be determined by a previously unknown gene: high anthocyanin con-
tent of fruits and foliage (figure 3) from the LA434 population segregates in
this fashion. In backcrosses of L. esculentum, the purple flush of the fruit has
not been recovered, but the recessive homozygotes can be clearly identified
by the intense anthocyanin coloring of leaves under cool growing conditions.
This new gene is provisionally named atroviolaceum (atv).

The very high level of inbreeding that must exist in these populations
provides ideal conditions for the fixation of such genes and the rapid differ-
entiation of races. It is very likely that the observed monogenic variations
arose from mutations in the Galapagos material and it is tempting to suppose
that at least some of them have been fixed purely at random without reflecting
selective advantage.

Distribution

All of the foregoing evidence reveals an extremely high level of uni-
formity within populations of the Galapagos tomatoes. With minimal excep-
tions among the whole group, it is therefore valid to equate a single popula-
tion with a single genotype, thereby simplifying the visualization of geographic
distribution. Figure 5 illustrates graphically the distribution for variation in
four key morphological characters. The presence and intensity of expression
of these characters is symbolized by Anderson's (1949) familiar ideograms.
According to the scheme adopted. Gal. ppn. and var. minor are the contrasted
extremes, the latter being represented in figure 5 by a solid circle with three
long appendages and the former by an empty circle without appendages. Only
those populations are included that have been grown in culture or for which
adequate herbarium specimens exist.

It is evident from this summary of geographic distribution that var. minor
is widespread throughout the archipelago, lacking in only four of the larger
islands, possibly for reasons of inadequate collections. Gal. ppn. appears on
at least four of the main islands and is as widely distributed as the preceding

Figure 4. Typical pattern of variation in seedling progenies. Each family, appearing to
the right and above its respective number, is the progeny of a single plant collected in the wild.
Family 471 and 474 are typical L. cheesmanii. Family 472 and 473 are L. esculentum var. minor.
(1/4 Reduction)

No. 44)

RICK: GALAPAGOS SYMPOSIUM

[470

[4.0

[4743

SPa^w

C473: ;;;

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

form in respect to longitude. Typical L. cheesmanii, represented in figure 5
by a half-solid circle and single vertical appendage, is distributed to three
and j>erhaps four larger islands.

Such widespread distribution of single biotypes contrasts strikingly with
the narrow endemism of many other components of the Galapagos biota. To il-
lustrate this contrast, figure 6 has been prepared to show the distribution of
Scalesia species according to Howell's (1941) monograph. In this familiar ex-
ample of Galapagos endemism, all but five of the nineteen well distinguished
species are restricted to single islands. It is safe to speculate that at least
part of this difference in distribution reflects differences in dispersal ability of
the two genera. As already stated, the very close approach of var. minor to the
strand of several islands suggests that this form might occasionally be distrib-
uted by the sea. Experiments with seed germination, presented in the next sec-
tion, offer additional suggestions as to mechanisms of interisland dispersal.

Another hint of successful dispersive ability of the Galapagos tomatoes
is given by evidence of their recent invasion of new habitats. Some popula-

Hoirs

3rd order leof

divisions
Intemode length

Colyx lorge ft
Decrescent

L pimpinel-
li folium

noneO
noneo

long
no

L esculentum
vor minor

mony^
much n

short o
yes '~^

Figure 5. Geographic distribution of races of Galapagos tomatoes. All islands are shown
except the northernmost two, Culpepper and Wenman, from which tomatoes have not been re-
ported. The population phenotypes are indicated by ideograms according to Anderson (1949).
Galapagos L. pimpinellifolium is represented by an open circle; L. esculentum var. minor, by a
solid circle with three long appendages; and typical L. cheesmanii, by a half-solid circle with
a single vertical appendage.

No. 44)

RICK: GALAPAGOS SYMPOSIUM

Figure 6. Geographic distribution of species of Scalesia (after Howell, 1941). All islands
are shown except the northernmost two, Culpepper and Wenman. Species are designated by the
following symbols: af - S. affinis, as - aspera, at - atractyloides. B - Baurii, co - cordata, Cr -
Crockeri, Da - Darwinii, di - divisa, g - gummifera. He - Helleri, Ho - Hopkinsii, in - incisa,
m - micTocephala, p - pedunculata, V\-- var. typica, P2 - var. Svensoni, P3 - var. parviflora, P4 -
vaT.indurata, P5 - var. ^/7osa, t- retroflexa, Sn- Snodgrassii, St. - Stewartii, v-villosa, S. Snodgras-
sii has been collected from Wenman Island and an unidentified species from Culpepper Island.

tions— for example var. minor on Bartholomew Island— have been found growing
in crevices of lava flows in which the pristine condition of ripple marks at-
tests very recent volcanic activity. Also, native tomatoes have been collected
from areas where volcanic activity has been observed in historic times. Such
populations have been collected from at least six different places, including
the interior of the large central crater of Narborough Island, which suffered a
violent eruption in 1825. The Galapagos tomatoes are clearly well adapted to
migrate and colonize new areas. They are nevertheless endemic in the sense
that the whole group is restricted to the Galapagos Islands.

Seed Dormancy

The problem of seed dormancy will not be presented in detail here, since
this subject and the development of effective means of overcoming thedorman-

70 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

cy are treated by Rick and Bowman (1961). In summary it was found that all
seeds of any races of Galapagos tomatoes thus far acquired show a severe
dormancy, which is not corrected by prolonged storage. Of the many different
treatments applied, the only ones effective in improving germination were meth-
ods that partially or wholly removed the seed coats. The behavior of the seeds
in those tests suggests that the inhibition is simply mechanical: once the
seed coat is partly or entirely removed, the radical emerges rapidly. The simp-
lest and most effective treatment was found to be the exposure of seeds to
strong solutions of sodium hypochlorite. In a search for mechanisms that might
permit natural establishment of the Galapagos tomatoes, it was found that
passage of the seeds through the digestive tract of the giant Galapagos tor-
toise, Testudo elephantopus porteri resulted in improvement of germination of
war. minor from 1 to 85 per cent and of Gal. ppn. from 1 to 11 percent. Two to
four weeks were required for passage through the tortoise gut. If this is a na-
tural mechanism for establishment, it would be effective not only in permitting
germination but also in expediting dispersal by virtue of the long digestive
period. Dependence upon animal digestion poses some interesting evolutionary
problems. The selection and establishment of such a dependency would seem-
ingly call for much trial and error and would likely require a long period for
establishment.

If animals play a major role in breaking the tomato seed dormancy, the
question might be asked: to what extent are they responsible for the present
distribution of Galapagos tomatoes? The role of the tortoises is problematic:
if they were responsible to any large degree for dispersal of the native toma-
toes, the endemic distribution of the tortoises themselves would be contradic-
tory. Beebe (1922) has ascertained that the tortoises can survive and swim in
sea water. On the other hand, safe landings on the hazardous Galapagos shores
are another matter. Yet, death or severe injury to a tortoise at landing would
not necessarily preclude establishment of the tomatoes. This problem is ob-
viously complex and has many facets; nevertheless, the possibility of inter-
island dispersal by tortoises as a rare event cannot be precluded at the pres-
ent state of knowledge. Other possible agents are marine or such terrestrial
bird species that can migrate from one island to another. The only likely avian
agents, however, would be those with a mild digestive action— for example, the
Galapagos mocker— for tomato seeds do not tolerate much grinding by gizzards.
The two native species of iguana might also be implicated.

A treatment of the tomato distribution would not be complete without
consideration of the effects of possible early changes in the configuration of
the archipelago. The ocean floor is so shallow in the Galapagos area that only
slight lowerings of the water level or elevations of the land masses would re-
sult in land connections between various islands. Under such conditions wide-
spread dispersal of the tomato races would not have presented serious diffi-
culties.

No. 44)

RICK: GALAPAGOS SYMPOSIUM

Compatibility Tests

Various accessions of Galapagos tomatoes have been subjected to rou-
tine tests of cross-compatibility among themselves and between them and other
species of tomatoes. These tests have been conducted in the spring and fall
seasons under standard greenhouse conditions at Davis, California. Five to
ten plants of each accession were used for the matings and six or more flowers
were pollinated in each combination tested. The results of these hybridiza-
tion experiments are presented in graphic form in figure 7. The tests consis-
tently revealed absence of severe barriers to crossing between the two most
widespread races from the Galapagos, var. minor and Gal. ppn. and L. esculen-
tum, L. pimpinelli folium (typical form from the mainland), L. hirsutum, L. min-

^ 0 S t^^CEss

'0^

esculentum

pimpine
lifolium

L
minutum

L.
chilense

Figure 7. Compatibility polygon indicating the degree of compatibility between Galapagos
forms and other tomatoes. The width of connecting lines indicates the relative amount of hy-
brid seed produced by the hybridizations, the widest lines being equivalent to complete com-
patibility as measured by the yield of selfs or sibs within the race. A dotted line indicates
failure of hybridization. Circled numbers refer to specific accessions. All accessions that are
intercompatible and behave similarly in all test crosses to Galapagos races are enclosed in
larger circles.

72 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

utum, and Solanumpennellii [which in these and other tests (Rick, 1960) shows
a much closer genetic relationship with Lycopersicon than Solanurn\. Seeds
produced by these crosses yielded F^ hybrids that were vigorous in all com-
binations and fertile in all save combinations with S. pennellii. On the other
hand, very severe barriers prevent crossing with L. chilense and L. peruvian-
um, none of the hundreds of attempted crosses yielding hybrid progeny.

In addition to the aforementioned tests, thirteen other Galapagos acces-
sions (seven of Gb\. ppn., three oivar. minor, two ofL. cheesmanii, and one of
the intermediate type from Albemarle) were hybridized with L. esculentum.
These crosses likewise produced normal yields of seeds, and the hybrids and
backcross generations to L. esculentum grown therefrom displayed normal vig-
or and complete fertility. Although these additional collections were not sys-
tematically tested against each other and the other tomato species, it is a
foregone conclusion that they would manifest the same compatibility relations
as the two accessions (LA166 and 317) that were tested more extensively. The
Galapagos tomatoes therefore comprise an interfertile group of races that hy-
bridize freely with L. esculentum and other species of the L. esculentum com-
plex.

The complete compatibility between Galapagos tomatoes and members
of the L. esculentum complex was entirely unexpected because the latest tax-
onomic treatments (MuUer, 1949; Luckwill, 1943) placed the former in the
same subsection as L. peruvianum and L. chilense. From the standpoint of
tomato genetics and breeding this finding was a pleasant surprise, for it meant
that the whole gamut of variation in Galapagos tomatoes is available for trans-
fer to L. esculentum by applying the appropriate breeding techniques. Although
it is not the main objective of this paper to consider applications in the area
of genetics and breeding, some of the findings are illuminating from the stand-
point of systematics and phylogeny. To date a number of interesting charac-
ters have been transferred by backcrossing from Galapagos races to the gar-
den tomato. Backcrosses from all of 15 different accessions, including the
main races, have recovered the gene B, which diverts synthesis of the fruit
carotenoids entirely to beta-carotene. The presence of this gene accounts for
the yellow and orange fruit color in all accessions of Galapagos tomatoes.
Other monogenic traits that have been encountered are the aforementioned /2,
ag, l-^, and atv. Of this group of genes, ag and l-^ behave normally in back-
crosses to L. esculentum, But /2 induces unexpected pleiotropic effects on
floral parts, and the effects of atv seem to become diluted in the sense that
the intense anthocyanin pigmentation develops on the herbage but not on fruits
of backcross derivatives. Still other characters have been encountered in the
derivatives, which were unknown in the wild parent. Examples of such "sur-
prise" characters are elongate fruits, a thick, leathery calyx, and a pedicel
joint that has normal morphology yet fails to abscise. The mode of inheritance
of these characters has not yet been ascertained, but the limited available

No. 44) RICK: GALAPAGOS SYMPOSIUM 73

data suggest simple genetic determination probably by recessive genes. Un-
doubtedly such latent characters owe their appearance to a complementary in-
teraction between genes from the wild parent and the genotype of the culti-
vated tomato. Since extensive breeding tests are required to reveal these la-
tent characters, only a slight beginning has been made in the survey of this
source of new germ plasm.

Natural Relationships

According to all available evidence the races of Galapagos tomatoes
are closely related among themselves. All genuinely native accessions pos-
sess in common at least five unique traits, which are, except for B, unknown
in any other wild tomatoes. No barrier, whether relating to incompatibility,
vigor or fertility of F-j^or later generations, has been found to their interbreed-
ing. The same freedom of hybridization has been revealed between them and
L. esculentum and closely related species. If all the facts are taken into ac-
count, separation of the group into different species can scarcely be justified.
The taxonomic status of the whole group, on the other hand, is problematic.
By morphological criteria alone, it should be recognized as a species. Yet the
genetic evidence points to such a close relationship with L. esculentum that
a rank above subspecies would not be justified: geographic isolation may be
the only factor presenting merging and intergradation with forms of the latter
species. Clearly then, although changes in the nomenclature are needed, any
decision must be to some extent arbitrary. Since the taxonomy of the group is
not the primary objective and complete taxonomic documentation not appro-
priate here, no systematic revision is currently proposed.

The above conclusions differ from those reached in an earlier study
(Rick, 1956) based on herbarium material and experiments with living material
of three accessions. The three were treated as L. esculentum vai. minor (LA-
317), L. pimpinellijolium (LA166), and L. esculentum var. cerasifoTme (LA-
292). That study suffered the shortcomings of inadequate living collections
and lack of first-hand experience in the native habitat. In the meanwhile the
opportunity to study living plants in many populations in the Galapagos and
in experimental cultures has shown unequivocally that LA292, though correct-
ly classified in 1956, is not native but likely excaped from nearby gardens in
the same fashion as many other cultigens in the Galapagos. When this item is
removed from the scene, homogeneity is evident between the two remaining
collections and all other known truly native tomatoes.

Origin of the Galapagos Tomatoes

The conclusions reached in the earlier survey (Rick, 1956) concerning
the origin of Galapagos tomatoes are largely fortified by the new evidence.
In respect to the elimination of LA292 from consideration as a native form.

74 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

the picture is, in fact, simplified. These conclusions can be briefly summar-
ized as follows. The closest approach to the Galapagos tomatoes in terms of
morphology and genetic compatibility is found informs of L. pimpinellifolium
from coastal Ecuador and Peru, although the former are well distinguished by
their aforementioned exotic traits. Of these unusual features, orange fruit col-
or (B), the accrescent calyx, and extreme hairiness of vegetative parts found
in var. minor also appear in L. hirsutum, also native to the Ecuadorean coast.
Whatever differentiation occurred in the origin of the Galapagos elements, it
was expedited by their high level of self-pollination.

The problem of origin has two aspects: determination of the ancestral
forms from the mainland and differentiation of races on the Galapagos. In com-
mon with most endemic groups of the archipelago, the two events might not
have been independent; differentiation of races might have begun before mi-
gration; although this process appears less likely than the migration of a sin-
gle stem line. •;

Any attempt to specify ancestral forms is fraught with the usual prob-
lems of gaps in the record: absence of a reliable fossil record, uncertainties
about the geological history, and others. If the new data contribute in any way,
they reinforce the implication of L. pimpinellifolium and L. hirsutum or some
extinct closely related forms. The former provides the closest approximation
in total morphology to the Galapagos tomatoes; the latter could have furnished
some of the exotic traits. The B gene previously found to be exclusive in L.
hirsutum, LA166 and LA317 has been detected in every living collection from
the Galapagos, and it seems safe to extrapolate that it exists in all Galapagos
tomatoes. All accessions of var. minor, including living and herbarium mater-
ial, possess in common the aforementioned accrescent calyx and excessive
hairiness. In addition, one of the latent traits revealed in the new studies— a
thick leathery calyx -points again to L. hirsutum. This new character is iden-
tical in appearance with fleshy calyx (fl), a monogenic trait bred into L. escu-
lentum from L. hirsutum (Butler, 1952), although a genetic test of identity has
not yet been made. Taken together, the data suggest a relationship between
the Galapagos tomatoes and L. hirsutum. Little more is revealed, however,
and it is highly uncertain how they came to share these genes. Since L. hirsu-
tum and L. pimpinellifolium differ extensively in a great welter of other morph-
ological and physiological characters, it is tempting to suppose that hybridi-
zations between the progenitors of the two led to introgression of a few genes
from the former into the latter to form the stem line of the Galapagos tomatoes.

It was pointed out in the early survey that self-pollination could have
played a key role in the differentiation of the group. The recently acquired
evidence from progeny tests, population variability, and activity of insect
vectors reinforces the conclusion that the Galapagos tomatoes are very highly
self-pollinated. Such a reproductive system guarantees a maximum opportun-

No. 44) RICK: GALAPAGOS SYMPOSIUM 75

ity for rapid differentiation of biotypes and for fixation of genes. It could also
account for the anomalous frequency of fixed monogenic abnormalities appear-
ing in some or all individuals of certain populations. Nothing remotely com-
parable to the fixation in whole populations of such genes as / l-i , or ag is
known in any other wild tomatoes. Although guessing at the adaptive value
of such characters is always hazardous, it is tempting to suppose that the sur-
vival in similar environments of genes that on the one hand control loss (ag)
and, on the other, intensification (atv) of anthocyanin is a random process.
Also it is difficult superficially to perceive a selective advantage for partial
loss of chlorophyll f/]^) or complete loss of pedicel articulation C/o).

Genetic variation within populations was found at only very low levels
in the intensively studied examples. Otherwise the only evidence of appre-
ciable genetic variability was found inLA438 on the coast of Albemarle. Even
in this instance, however, the variants were not products of immediate genetic
segregation, for progenies of the tested plants bred true. The responsible gen-
etic segregation, if any, must have occurred earlier, possibly many genera-
tions earlier. The unique variation in this population is accompanied by an-
other unique feature: the sympatric occurrence of var. minor and Gal. ppn. in
the vicinity of LA438. This remarkable coincidence strongly suggests that
the observed variation stemmed from introgression between the latter two races.

The mode of derivation of the various races of Galapagos tomatoes re-
mains highly conjectural. The high rate of self-fertilization and the widespread
and occasional sympatric distribution of the three dominant races suggest
that these races originated by natural selection from an ancient, variable stem
line. Segregants from the introgression of L. pimpinellifolium and L. hirsutum
and/or natural mutation might have provided the variable milieu from which
these successful races emerged. From their original sites they could have
spread together or separately throughout the archipelago. The aspects of dis-
persal and colonization of these races are discussed in the sections on dis-
tribution and seed dormancy. The other, rarer races might have originated in
the same fashion or by introgression from sporadic hybridization as suggested
by LA438.

If the proposed origin of the Galapagos tomatoes in L. pimpinellifolium
and L. hirsutum is correct, attention would be directed to the immediate main-
land of Ecuador and north coast of Peru. Although forms of L. hirsutum occur
elsewhere, the ones most compatible with the L.escw/erz^ww complex are found
in the above region. In this respect the tomatoes provide another example of
the many ecological and botanical ties between these continental areas and
the Galapagos outlined by Svenson (1946). Transport to the islands from the
adjacent coast is favored by several oceanographic features. In the first place,
the prevailing Humboldt Current sweeps northwestward alongthe coast of Peru,
and Ecuador whence it veers westward toward the Galapagos. In the second
place, the ocean floor rises to form the Carnegie Ridge, which extends from

76 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

the Galapagos toward continental Ecuador, being separated from the latter by
a narrow but deep trench (Shumway, 1954). If this ridge emerged above sea
level at an appropriate time it might have aided the migrations of tomatoes
and other forms of life to the Galapagos.

Summary

The Galapagos tomatoes comprise a group of closely related races pos-
sessing in common five exotic morphological and physiological traits, in which
they differ from most other species of the genus Lycopersicon. The three com-
monest races are relatively well distributed throughout the archipelago and
account for nearly all individuals of known populations.

All observations on floral structure, pollination mechanisms in nature
and in culture, population structure, and progeny tests point to a very high
level of self-pollination. Appreciable genetic variability between individuals
was discovered in one wild population, although the individuals bred true for
their deviating phenotypes in progeny tests. Otherwise the extent of genetic
variation between plants in a single population is so low that most individuals
conform to a single phenotype. Various recessive genes of well distinguished
phenotype are fixed throughout certain populations and appear in a small pro-
portion of individuals of others. Considerable genetic differentiation is evi-
dent between populations but is not much greater between islands than between
populations on the same island. The inbreeding consequent to automatic self-
pollination readily accounts for such population characteristics.

Seeds of Galapagos tomatoes are minute and seldom germinate without
treatments that remove or soften the seed coats. Passage through the digest-
ive tract of the Galapagos tortoise improves germination, revealing a likely
mechanism of natural dispersal and establishment.

All tested Galapagos accessions are completely inter-compatible and
cross-compatible with L. esculentum, L. pimpinellifolium, and other closely
related entities. All such combinations tested yield viable, completely fer-
tile F^ , Fo, and BC hybrids. Like other members of the L. esculentum com-
plex, they are separated from L. peruvianum and L. chilense by severe com-
patibility barriers. In common with all other known species, the Galapagos
tomatoes have twelve pairs of chromosomes.

According to the available evidence, all genuinely native Galapagos to-
matoes should be treated as sub-specific forms of a single species of the L.
esculentum complex. While they are approached most closely in morphology
by L. pimpinellifolium, certain other traits are to be found in L. hirsutum, both
of these species being native to the adjacent mainland. On the basis of these
and other facts, suggestions are presented to account for the origin and differ-
entiation of the Galapagos tomatoes. Rapid evolution of diverse races was
undoubtedly promoted by the strictly autogamous breeding system. Dependence

No. 44) RICK: GALAPAGOS SYMPOSIUM 77

upon animal digestion for establishment might account for the widespread dis-
persal of certain races.

Literature Cited

Anderson, E.

1949. Introgressive hybridization. Wiley, New York. 109 pp.

BEEBE, W.

1924. Gala'pagos: world's end. G.P.Putnam's Sons, London. 443 pp.

Butler, L.

1952. The linkage map of the tomato. Journal of Heredity, vol. 43, pp. 25-35.

Howell, J. T.

1941. The genua Scalesia. Proceedings of the California Ac ademy of Sc iences,
4th ser., vol.22, pp. 221-271.
HURD, P. D., Jr.

1958. The carpenter bees of the eastern P acific Oc ean islands. Journal of the
Kansas Entomological Society, vol.31, pp. 249-255.
LUCKWILL, L. C.

1943. The genus Lycopersicon; an historical, biological, and taxonomic sur-
vey of the wild and cultivated tomatoes. Aberdeen University Stud-
ies, 120 pp.

Muller, C. H.

1940. A revision of the genus Lycopersicon. United States Department of Agri-
culture Miscellaneous Publications, 382 pp.

RICK, C. M.

1950. Pollination relations of Lycopersicon esculentum in native and foreign

regions. Evolution, vol. 4, pp. 110-122.

1956. Genetic and systematic studies on accessions of Lycopersicon from
the Galapagos Islands. American Journal of Botany, vol. 43, pp.
687-696.

1960. Hybridization between Lycopersicon esculentum and Solanumpennellii:

phylogenetic and cytogenetic significance. Proceedings of the Na-
tional Academy of Sciences, vol. 46, pp. 78-82.

RICK, C. M., AND R. L Bowman

1961. Galapagos tomatoes and tortoises. Evolution, vol. 15, pp. 407-417.

Shumway, G.

1954. Carnegie Ridge and Cocos Ridge in the east equatorial Pacific. Journal
of Geology, vol. 62, PP. 573-586.

SVENSON, H. K.

1946. Vegetation of the coast of Ecuador and Peru and its relation to the Ga-
lapagos Islands. I. Geographical relations of the flora. American
Journal of Botany, vol. 33, pp. 394-426.

COMPOSITION AND RELATIONSHIP

OF THE TERRESTRIAL FAUNAS OF EASTER,

JUAN FERNANDEZ, DESVENTURADAS,

AND GALAPAGOS ISLANDS *

Guillermo Kuschel

Centra de Investigaciones Zoologicas
Universidad de Chile
Santiago, Chile

South America has a great number of offshore islands, particularly in
the fjord region of southern Chile, but there are also other truly oceanic is-
lands lying far from the mainland and composed entirely of volcanic material.
In this paper I shall attempt to present a general account of the composition
of the terrestrial faunas of the oceanic islands, and to show their relationships
with the faunas of other regions, before discussing the origin and possible
antiquity of their older elements. Easter Island, Juan Fernandez, Desventura-
das, and the Galapagos will be considered here, but the isolated Salay Gomez
and the Cocos and Malpelo islands will not be dealt with because they are
not sufficiently well known. In table 1 is shown the location of the islands to
be considered, together with other basic data (see also fig. 1).

Easter Island

This remote island has a low and uniform topography relieved by a few
craters which have no human record of volcanic activity. It is fairly arid, hav-
ing no streams, lakes, or swampland, and showing surface water only in the
depths of three of the craters. Its climate is warm-temperate, with its rainfall
evenly distributed through the year (Cfa in the Koppen-Geiger classification).

It is the only island of the four with a native human population. Man
and his domestic animals, particularly sheep, have been largely responsible
for the impoverishment of the flora and for this reason Easter Island has only
31 species of flowering plants. Skottsberg, in 1928, was therefore able to say

♦ Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science

Association, held at the University of Hawaii, Honolulu, Hawaii, U. S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-79-

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

-©

PASCUA (Easter)
Lat. 27° 10'
Long. 109° 26'
Area 118 km^
Alt. 530 m
Rainfall 1149 mm
Temp. 20.4 C

GALAPAGOS
Lat. 00°00'
Long. 89° 00'
Area 7643 km^
Alt. ISOO m
Rainfall 665 mm
Temp. 23.6 C

PANAMA

COLOMBIA

ECUADOR

- 5

- 10

- 15

PERU

DESVENTURADAS

Lat. 26° 19'
Long. 79° 47'
Area 7 km ^
Alt. 478 m
Rainfall + 600 mm
Temp. 17.3 C

JUAN FERNANDEZ
Lat. 33° 44'
Long. 78° 50'
Area 185 km
Alt. 1500 m
Rainfall 1152 mm
Temp. 15.3 C

- 20

CHILE

- 40

- 55

No. 44)

KUSCHEL: GALAPAGOS SYMPOSIUM

Table 1. Data on four island groups of the southeastern Pacific Ocean.

PASCUA

JUAN FERNANDEZ

DESVENTLIRADAS

GALAPAGOS

(Easterls.)

Latitude

27° 10' S

33° 37' S

26° 21' S

00° 00'

Longitude

109° 26' W

78° 52' W

79° 47' W

89° 00'

Area (km )

118

185

7643

Max. altitude (m)

530

1500

478

1500

Ann. Temp. C.

20.4

15.3

17.3

23.6

Rainfall (mm)

1149.3

1152.2

600

665

Distance from

continent (km )

3760

666

859

950

in all fairness, "there does not exist another Island of the size of Easter and
with such a fine climate where the native flora is so poor."

Although we would not expect a rich fauna on Easter Island it is quite
clear that the fauna has become further impoverished and it is possible to
point to certain features which, in this respect, distinguish Easter Island from
others under consideration:

(1) The cosmopolitan or wide-spread element in its fauna is very high,

(2) The Indo-Malayan, or Pacific, element is also appreciable.

(3) Of the 79 terrestrial species of animal life only six are endemic and
the position of even some of these is still debatable. These endemic species
are:

a) Chrysopa skottsbergi Esben Petersen, 1924 (Neuroptera)

There is nothing published on its relationships with other species
but it was most likely introduced from South America.

b) Lipsana insulae-paschalis Enderlein, 1940 (Diptera)

For this species Enderlein created a genus but gave no account
at all of its relation to other genera. He also raised a new sub-family which
he put in the Lonchaeidae.

c) Bidessus skottsbergi Zimmermann, 1924 (Coleoptera: Dytiscidae)

This is said to be extremely close to two Australian species.

d) P acindonus bryani (Swezey, 1921)

(Coleoptera: Curculionidae: Cossoninae)
The genus Pacindonus Kuschel is of Indo-Madagassian origin but
is widely distributed through the Pacific. It has a dozen species or so, and
is not represented in the Americas or in the cold-temperate regions.

Figure 1. Schematic position ofthe islands. Vertical line: South American con-
tinent, with the parallels. Horizontal line: the equator. Arrows: main relationships of
the terrestrial fauna.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 2. Climatological data for Easter Island.

LATITUDE 27° 10' S

LONGITUDE

109° 26* W

ALTITUDE 41 m

Mean max.

Mean Temp.

Mean m in.

Relative

Rainfall

temp. C.

Humid it y

mm .

January

27.0

23.1

19.1

104.9

February

28.2

23.7

19.6

78.6

March

27.4

23.1

19.3

100.9

April

25.5

21.5

17.8

120.7

May

23.4

19.9

16.9

114.7

June

21.9

18.3

15.1

116.5

July

21.4

17.8

14.6

88.6

August

21.5

17.8

14.7

85.7

September

22.1

18.1

14.5

75.7

October

23.3

19.1

15.2

70.6

November

24.2

20.2

16.3

90.5

Dec ember

25.5

21.8

17.9

101.9

Annual

24.3

20.4

16.8

1,149.3

Years of

observation

e) Tetragnatha paschae Berland, 1924 (Araneae)

The genus is of world-wide distribution and this species may pos-
sibly occur in other Pacific Islands.

f) Melampus pascus Odhner, 1922 (Mollusca)
This is of Oriental origin.

Of the six endemic species so far known, three are of Oriental origin,
one of Australian origin, and the origin of two is as yet undetermined. So far,
then, there is no proven South American element in the fauna, and Easter Is-
land must be considered as one of the Pacific islands which have the Indo-
Malayan element as the strongest in their faunas.

Juan Fernandez

This is really a small archipelago comprising the islands of Masatierra,
Santa Clara, and Masafuera, and Santa Clara may be counted a continuation
of Masatierra, for it is separated from the western tip of the latter only by a
narrow channel. Both Masatierra and Masafuera have a dense but varied cover
of vegetation and this is particularly well developed around the higher hills
of Masatierra. Only 170 km. (92 miles) separate Masatierra and Masafuera,
yet each has its own endemisms. Masafuera tops Masatierra by 600 metres,

No. 44)

KUSCHEL: GALAPAGOS SYMPOSIUM

Table 3- Composition of the terrestrial fauna of Easter Island.

ENDEMICS

S. AMERICA

ORIENTAL

AUSTR-
NEOZ.

WIDE
SPREAD

UNDEFINED

Oligochae ta

• ■

• •

Isopoda

• •

Myriapoda

••

Insecta

(4)

(-)

(8)

(1)

(42)

(2)

Coll embola

Odonata

. .

Blattariae

Orthoptera

■ •

Embioptera

• •

Dermaptera

• •

Thysanoptera

■ •

Psocoptera

• •

Hemiptera

• •

Ne uroptera

Lepidoptera

Diptera

Coleop tera

Hymenoptera

••

Araneae

Mollusca

••

■•

Vprtebrata

••

-•

Total

Table 4. Relationships of the

fauna of Easter Island.

S. AMERICA

AUSTRALIA

ORIENTAL-
POLYNESIAN

WIDE
SPREAD

UNDEFINED

Number of species
Percentage

••

2
2.53

20.25

52
65.82

9
11.39

its peaks are covered with snow in winter, and light falls of snow are common
in summer. It is on these summits that the interesting Magellanic element of
its flora is found.

Both islands have some permanent streams but they lack lakes and
swampland. There are no volcanic craters aDthough an eruption a century and
a quarter ago (1835) took place off the extreme south-east of Cumberland Bay
on Masatierra close to the coast.

Juan Fernandez has a warm temperate climate with rain throughout the
year, but with considerably more precipitation in winter than summer (Csb2

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 5- Climatological data of Juan Fernandez (Masatierra).

LATITUDE 33° 37' S

LONGITUDE 78° 52' W

ALTITUDE 6 m.

Mean max.

Mean temp.

Mean m i n .

Rel ative

Rainfall

temp. C.

temp. C .

Humidity

mm.

January

21,7

18.4

15.2

24.9

February

22.0

18.9

15.6

30.1

March

21.0

18.3

15.1

39.8

April

19.7

16.8

13.4

82.4

May

17.8

15.2

12.0

149.0

June

16.0

13.7

10.5

160.3

July

15.1

12.9

9.8

142.0

August

14.7

12.3

9.2

113.8

September

15.2

12.4

9.4

76.8

October

16.2

13.3

10.2

54.5

November

18.0

15.0

11.7

34.2

Dec ember

20.0

17.0

14.0

26.4

Annual

17.9

15.3

12.2

1,152.2

Years of

observation

in the Koppen-Geiger classification). The lower-lying areas at some distance
from the hills have a very dry summer and an arid soil that applies to the ex-
treme west of Masatierra and to Santa Clara.

The flora includes 147 species of flowering plants. There are no native
species of amphibians, reptiles, fresh-water fish, or mammals, but there are
nine species of land-birds, all of which are related to the Chilean fauna.

According toSkottsberg (1956) there are 147 species of flowering plants
on Juan Fernandez, and of these 101 are endemic. He divided the 147 species
into 6 elements as below:

Andine Chilean element

Subantartic Magellanian element

Neotropical element

Pacific element

Atlantic-S. African element

Eu-Fernandezian element

It is most interesting to note here that the incidence of endemism, on a
percentage basis, is very similar in the insects and flowering plants. It is not
yet possible in the case of the insects to achieve the same precision of class-
ification by origin which Skottsberg made for the plants, but the literature
shows clearly enough that the southern Chilean element predominates strong-

46.9%

10.2%

12.9%

17.7%

4.1%

8.2%

No. 44)

KUSCHEL: GALAPAGOS SYMPOSIUM

Table 6. Composition of the terrestrial Arthropod fauna of Juan Fernandez.

ENDEMIC

NON-ENDEMIC

UNDEFINED

TOTAL NUMBER

GENERA

SPECIES

OF SPECIES

Isopoda

, ,

Myriapoda

Insecta

(54)

(440)

(170)

(77)

(687)

CoUembola

Thysanura

Orthoptera

• 1

Dermap tera

.•

Isoptera

P so cop tera

Thysanopt era

Hemip tera

Neuroptera

Trichoptera

Lepidoptera

Diptera

102

193

Coleoptera

191

235

Hymenoptera

1 1

Arane ae

• •

Pseudoscorpionida

A cari

• •

ly. Second in importance, as in the case of the plants, comes the Pacific ele-
ment, mainly Indo-Malayan.

Desventuradas

These consist of the two tiny islands of San Felix and San Ambrosio
and the islet called Gonzalez. This group lies 777 km. (420 miles) to the
north of Juan Fernandez and 859 km. (464 miles) from the nearest point of the
mainland.

San Ambrosio is larger, measuring roughly 4 km. long by 1 km. wide.
Its coastline is very steeply countered and its upper parts constitute a pla-
teau, lying between 300 and 478 metres above sea level, which is dissected
by a few small and shallow ravines. Surface water and filtrations through the
walls are totally absent except immediately after rain and for this reason the
island is uninhabitable. There are no meteorological data for the Desventur-
adas but it is known that there is abundant rain in winter, while from October
to March no rain falls and the summit is quite free from low clouds.

The prevailing wind is from the south-south-east. The vegetation is
halophytic and though abundant on the plateau it is very scarce on the cliffs
of the island. The island has only 19 native species of phanerogams and one
moss, and there are no ferns at all. Terrestrial vertebrates are non-existent,

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 7. Percen

tage of endemisms of Insecta

and Phanerogamae.

ENDEMIC

NON-ENDEMIC

UNDEFINED

TOTAL NUMBER

Insec ta
Phanerogamae

64.43
68.7

24.35
21.3

11.22

687
147

either native or introduced, but there are seven species of sea birds which
nest on the island and there is one land-bird which is probably only the Juan
Fernandez Sparrow Hawk (Falco sparverius fernandensis Chapman) which is
most likely a recent immigrant.

San Ambrosio is one of the very few islands which has so far avoided
invasionby any terrestrial vertebrates or by any weeds and has totally escaped
the effects of fire.

San Felix Island is only a little, way to the west of San Ambrosio. It is
smaller, lower (170 m. summit), and is less steeply sloped, it is much more
arid and its vegetation is very sparse. It has some eight species of phanero-
gams, two of which are endemic.

Table 8. Composition of the terrestrial Arthropod fauna of San Ambrosio.

ENDEMIC

NON-ENDEMIC

UNDEFINED

TOTAL NUMBER

GENERA

SPECIES

OF SPECIES

Isopoda

• •

••

Chilopoda

• •

••

Insecta

(4)

(16)

(21)

(37)

(74)

Collembola

Thysanura

Orthop tera

••

P socoptera

• •

Thysanoptera

Hemiptera

Lepidoptera

Dip tera

Coleop tera

Hymenoptera

••

Arane ae

Pseudoscorpionida

Acari

• •

(20)

Gamasides

Uropodina

Trombidiformes

Acaridiae

Oribatei

••

No. 44) KUSCHEL: GALAPAGOS SYMPOSIUM 87

A point worth noting in table 8 is that the lepidopterous species out-
number both the Diptera and the Coleoptera.

As the first intensive collecting of the small animal life took place only
at the end of 1960, much of the material yet remains to be determined by spe-
cialists. Although the flora of the island only slightly resembles that of Juan
Fernandez, the fauna is much more closely related. The percentage of endem-
ism seems. to be appreciably lower than on Juan Fernandez, but there are not-
able examples of endemism in both species and genera. Our knowledge to date
enables us to distinguish four endemic genera in the Insecta, a genus of Calli-
phoridae related to Callyntropyga of Juan Fernandez, two genera of Curculion-
idae (Cossoninae) found only on Thamnosens and related to the Juan Fernan-
dez fauna, and a carabid of problematical relationships, but certainly with no
closely related genera in Juan Fernandez or on the Chilean mainland. A few
other genera, formerly considered endemic in Juan Fernandez, are also repre-
sented on San Ambrosio, although not by the same species. It cannot be doubted
that the terrestrial fauna of the Islas Desventuradas is closely related to that
of Juan Fernandez unlike the flora which is only distantly related as a whole.

Galapagos

These islands form an archipelago situated on the Equator some 950 km.
(510) miles) from the nearest South American coast. They comprise 15 largish
islands together with a host of smaller islands. Their total area is more than
40 times greater than Juan Fernandez and they offer a wider variety of envi-
ronments, with arid and moist areas and with an altogether richer vegetation
as they have nearly four times the number of plant species.

The terrestrial vertebrate fauna is comparably well known but the same
cannot be said for the invertebrates. Information on the invertebrates is very
widely scattered, so that it is extremely difficult to obtain a concise overall
picture of the Galapagos fauna, but I have been able to collate all known pa-
pers on the Coleoptera and this is given in table 11 where it is compared with
data for Juan Fernandez.

Within any geographical zone there is a clear enough observable ratio
of flowering plants to insects. The ratio varies with the incidence of endem-
ism. On the basis of this ratio and the number of plants known to exist in the
Galapagos Islands one would expect to find at least 550 to 800 species of
Coleoptera, but up to now there are recorded only 190 species; that is to say,
between a third and a quarter of the expected number. Moreover, the usual ratio
of Carabidae to Curculionidae is roughly 1:5 and it is extremely strange that
more Carabidae than Curculionidae are recorded for the Galapagos. From these
facts we can only deduce that the Galapagos fauna has been selectively and
incompletely collected.

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 9. Climatological data of San Cristobal (Chatham I.}, Galapagos.

LATITUDE 00° 54* S

LONGITUDE 08° 37' W

ALTITUDE 2.7

Me an max.

Me an temp.

Mean min.

Relative

Rainfall

temp. C .

Humidity

mm.

January

28.7

24.8

21.9

5.5

February

29.8

25.8

22.9

190.1

March

29.8

25.9

22.6

241.5

April

30.0

25.9

22.8

141.8

May

28.6

24.9

22.2

14.9

June

27.8

23.8

21.4

5.2

July

26.4

22.7

20.7

6.8

August

25.6

21.7

19.6

8.4

September

25.0

21.1

19.0

6.0

October

25.5

21.7

19.2

6.8

November

25.8

22.2

19.9

10.8

December

27.1

23.2

20.9

26.6

Annual

27.5

23.6

21.1

664.4

Years of

observation

There is also a universally observed ratio between the endemism of
phanagerogams and of the fauna, this being particularly true of the insects.
From the table comparing the Coleoptera of the Galapagos and Juan Fernan-
dez we can see that the incidence of endemism of Coleoptera species is about
the same for both groups of islands, but for plants it is about 48 per cent for
the Galapagos and is 68.7 per cent for Juan Fernandez; this seems to point to
wrong interpretations in plant or Coleoptera studies somewhere, and the neces-
sity for an intensive collection of invertebrates in the Galapagos is very ap-
parent.

The Gala'pagos are further from the mainland than are the Desventuradas
and Juan Fernandez and both flora and fauna are typically Neotropical, with
few exceptions. A high percentage of the species of the Galapagos fauna has
been found, by many authors, to be most closely related to the faunas of Cen-
tral America, Mexico, and the Caribbean islands; but this is due more than
anything to our ignorance of much of the fauna between Panama and northern
Peru. Of the fauna I have personally been able to examine (Curculionidae), I
am quite certain that the most closely related mainland species are those
which live immediately opposite the Galapagos. There are some remarkable
examples of Galapagos species being extremely closely related to species on
Puna Island in the mouth of the Golfo de Guayaquil.

No. 44)

KUSCHEL: GALAPAGOS SYMPOSIUM

Table 10. Climatological data of Seymour Island, Galapagos.

Mean max.

Mean temp.

Mean min.

Rainfall

temp. C.

mm.

J anuary

29.4

2 5.9

22.5

16.5

February

30.0

26.8

23.6

29.7

March

30.1

27.0

23.8

16.5

April

30.0

26.7

23.5

20.6

May

29.2

25.7

22.2

1.0

June

28.6

25.1

21.7

0.2

July

27.1

24.0

20.8

0.2

August

27.1

23.3

19.7

0.2

September

26.8

23.1

19.5

0.0

October

27.1

23.3

19.6

0.0

November

27.5

23.8

20.1

0.0

December

28.2

24.6

21.0

0.0

Annual

28.3

24.8

21.4

85.6

Years of

observat ion

The occurrence ofendemism in species and plants in the Galapagos is
much lower than in Juan Fernandez.

The Origin of the Faunas of
Juan Fernandez, Desventuradas, and Galapagos

As has been mentioned earlier, all these islands have today a purely
volcanic bedrock and their degree of erosion has led geologists unanimously
to believe that the islands cannot possibly be older than the Pliocene; that is
to say, that they are not much more than ten million years old. We have to ask
if this relatively short time, by geological standards, is sufficient to account
for the clear difference observed between the faunas of the islands.

Geographically the Galapagos, Desventuradas, and Juan Fernandez are
roughly the same distance from the South American coast and the line joining
them is not far out of parallel with the line of the Andes. This makes one
wonder if they might not have a common tectonic origin. It is also worthy of
note that petrographic studies have shown very close similarity between the
rocks of Masafuera and the Galapagos.

On the origin of life in these islands much has been written but the opin-
ions expressed have differed greatly, expecially with regard to the Galapagos.
There are those who passionately maintain that winds, sea currents, and birds

90 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

are much more effective dispersal agents than is commonly conceded. That
such agents do play a part in the repopulation of islands is not doubted, but
as far as these particular islands are concerned it is easy enough to point to
a series of components of the fauna which could not have been so transported,
at least not across the natural barriers as they are today. I shall attempt to
tackle this problem, beginning with Juan Fernandez and the Desventuradas.

Geological studies have shown that the Chilean coast south of Valpa-
raiso had more or less the same coastline in the late Cretaceous as at the
present. During the Eocene, however, we know that an important movement
occurred between the 38th and 45th parallels, as this region completely lacks
Eocene sedimentary rocks, and the next marine sediments to appear are of late
Oligocene age, beginning with Navidad strata. This means that during the
Eocene and most of the Oligocene there was formed a continuous ridge of land
which cut off the present coast from the sea. This unstable mass was called
"Land of Juan Fernandez" by Briiggen (1950) and this distinguished geolo-
gist presumed that this land extended obliquely northwards to Juan Fernan-
dez, embracing the Desventuradas, for between these islands there is today
a submarine chain nowhere deeper than 1.430 m.

It is difficult to reconcile the proposed recent origin of the islands with
our certain knowledge that Juan Fernandez and the Desventuradas contain an
abundance of primitive elements in their flora and fauna and it is easier to ac-
cept Brilggen's hypothesis of the islands' origin. That is that, far from being
of Pliocene or Pleistocene age, the islands are the relics of an older exten-
sive land-mass which had direct connection with the continent or at least was
very much closer to it than are the islands today, so permitting dispersal of
the flora and fauna until the very late Tertiary when it is supposed a final
subsidence isolated the present-day islands which are basically volcanic cones.

On the basis of Briiggen's hypothesis, which is founded on some geolo-
gical facts, Skottsberg was able to understand and explain the Eocene flora
of Juan Fernandez and also the high incidence of endemisms in genera and
species. The occurrence of a subantarctic flora on the peaks of Masafuera,
however, is still not satisfactorily explained for the ocean currents cannot be
considered a likely means of transporting plants to island peaks, the present-
day winds do not lie in the right direction, and we do not now observe bird mi-
grations between southern Chile and Juan Fernandez. On the other hand, it is
interesting to note that the subantarctic element in the flora is not paralleled
in the fauna.

As far as the terrestrial fauna is concerned, with its remarkable degree
of generic and specific endemism and its high percentage of species related
to those in southern Chile, the hypothetical "Land of Juan Fernandez" accounts
completely for its presence in the islands. Nevertheless, I would like to draw
attention to two facts of importance:

No. 44) KUSCHEL: GALAPAGOS SYMPOSIUM 91

(1) The number of species of Coleoptera in the leaf litter is startlingly
low despite the favorable conditions for development of such a faunal group.
Most of the elements characteristic of southern Chile are missing, this being
especially true of the Pselaphidae, Melandryidae, and Curculionidae(Crypto-
rhynchinae.)

(2) Among the flying insects, such as the Neuroptera and especially the
Diptera, a large number of species are common to Juan Fernandez and south-
ern Chile, or at least extremely closely interrelated, but many of these are
found only in forests or their surrounds and not near the Chilean ports from
which ships set sail for the islands. This makes it almost impossible for these
species to have been transported to the islands by man 's agency. While on
the subject of flying insects, I might here interpolate some mention of certain
birds which can scarcely have reached the islands under their own power in
conditions as they are today; I have in mind such species as Spizitornis fer-
nandezianus, Cinclodes oustaleti baeckstroemi, and Aphrastura masafuerae.

The first point, concerning the Coleoptera fauna of the leaf litter, seems
to suggest that the Eocene fauna of the leaf litter lacked this element or, and
perhaps more likely, that the "Land of Juan Fernandez" was not entirely con-
tinuous but interrupted here and there sufficiently to prevent the dispersal of
those species belonging exclusively to the soil. We can hope to get nearer
the truth of this matter once the hypogeous fauna has been carefully studied.

There is another geological fact worth mentioning here. Along the whole
length of coast from the 5th parallel (Payta) in northern Peru to just beyond
the 32nd parallel (to the North of Valparaiso), there are found no marine sedi-
ments from the Eocene to the early Pliocene. This means that throughout this
considerable period the coastline must have lain in what is now the Pacific
Ocean, but we know nothing about this addition to the continental margin,
which disappeared only in the late Pliocene. It is worth repeating here that
the flora of San Felix and San Ambrosio is most closely related to that of Ata-
cama, the mainland region immediately opposite the islands, and I might add
that it is extremely difficult to account for this by means of the usual agents
of dispersion, for neither atmospheric nor sea currents run in the required di-
rection and birds do not now migrate from Atacama towards the islands.

On the origin of life on the Galapagos, if I may move on to this last
group of islands, much has been written and one might almost say that the
number of opinions equals the number of authors. If one compares its flora
and fauna with that of Juan Fernandez, it is immediately apparent that its in-
cidence of generic and specific endemisms is proportionally lower, and also,
that its species do not display, as a whole, so many primitive features. On
these grounds we do not expect such an early origin of life in the Galapagos
as in Juan Fernandez and the Desventuradas. As there is an ample evidence
of important geological changes throughout the whole of the Tertiary along

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 11. The Coleoptera o( Galapagos and J nan Fernandez compared.

Galapagos

Juan Fernandez

Genera

Endemic
genera

Species

Endemic
species

Genera

Endemic
genera

Species

Endemic
species

Cicindelidae

Carabidae

...

Dytiscidae

••

Gyrinidae

, ,

. .

Hydrophilidae

, ,

Limnebiidae

, ,

Staphylinidae

Ptiliidae

, ,

Scaphidiidae

, ,

Histeridae

, ,

Passalidae

Scarabaeidae

IC)

2(?)

. ,

Trogidae

.«

, ,

Cantharidae

, .

, ,

Lycidae

, ,

Meloidae

. .

Mordellidae

Tenebrionidae

Alleculidae

Monotomidae

Oedemeridae

Nitidulidae

Cucujidae

Cryptophagidae

Languriidae

, ,

Cisidae

Lathridiidae

Colydiidae

Mycetophagidae

• •

, ,

Elateridae

Melasidae

, ,

Buprestidae

• •

••

• •

Ostomidae

Cleridae

• •

Dasytidae

• •

Dermestidae

• •

Anobiidae

Bostrichidae

(+Lyctidae)

••

• •

Coccinellidae

Cerambycidae

• •

••

Chrysomelidae

Bruchidae

••

• •

••

Anthribidae

Curculionidae

126

120

Scolytidae

• •

••

Platypodidae

••

Total

107

190

152

235

191

No. 44)

KUSCHEL: GALAPAGOS SYMPOSIUM

Table 11. Continued

Galapagos

Juan Fernandez

Genera

Endemic
genera

Species

Endemic
species

Genera

Endemic
genera

Species

Endemic
species

Families (total)

Families with
endemic subspec

ies

Percentage of
genera

94.4

5.6

73.5

26.5

Percentage of
species

18.74

81.26

the rest of the South American coast, we might expect there to have been sim-
ilar disturbances along the coast of Ecuador and Colombia and, in fact, there
is evidence of changes in short level in some fossiliferous raised beaches of
late Tertiary age. The two submarine ridges, the Cocos Ridge which runs from
Costa Rica to the north of the Galapagos, and the Carnegie Ridge which runs
from Ecuador to the same islands, suggest a possible former union or Closer
proximity of islands and mainland. Shumway, however, discounts the former
ridge by saying "the apparent absence of truncated seamounts on Cocos Ridge
is evidence against a former emergence." Of the other submarine feature he
says "on the basis of the bathymetry of Carnegie Ridge and the geological
history of Colombia and Ecuador, it is speculated that the easternmost por-
tion of Carnegie Ridge may once have been part of the western borderland for
the early Tertiary geosyncline which existed along the present coastal low-
land of western Ecuador. This would have shortened the sea route to the Ga-
lapagos Islands and possibly facilitated the rafting of plants and animals to
the Islands."

The foregoing shows that there is yet no geological evidence of a land
connection between the Galapagos and the continent in recent times and, in
fact, dates any such connection as early Tertiary at the latest. This, however,
hardly does more than deepen the mystery as the very close relationships be-
tween animal and plant species on the Galapagos and the continent are most
striking and unquestionable, while other species on both mainland and islands
are identical. If the origin of life in the Galapagos is placed as far back as
the early Tertiary, then it seems impossible to understand the much lower de-
gree of speciation and specialization of the terrestrial organisms on the Gala-
pagos in comparison with those on Juan Fernandez, especially as the more
favorable climate produces a higher turnover of genetic material. One would
therefore expect to find an even greater difference in species between the Ga-
lapagos and the mainland than between Juan Fernandez and the continent. If

94 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

I might be permitted to express a personal view, I would say without much
hesitation after having studied my own group of the fauna of all the islands,
and making the considerable assumption that one can extrapolate from this
group, that the Galapagos' fauna is considerably younger than that of Juan
Fernandez and the Desventuradas. I would also say that the fauna of these
last two remote groups of islands mostly dates back to the Eocene and part of
of the Oligocene, while the Galapagos fauna, including the terrestrial verte-
brates, might go back only to the Pliocene or, even, to the end of the Plio-
cene and to the Pleistocene.

Summary

After a brief description of Easter Island, Juan Fernandez, the Desven-
turadas, and the Galapagos, there follows a general account of the terrestrial
faunas and their relationships with other biogeographic regions. All the base-
ment rock now visible on the islands is volcanic and young in geological time,
probably of the late Pliocene.

The incidence of endemisms in species, genera, and even higher sys-
tematic categories is considerably more in Juan Fernandez and the Desven-
turadas than in the Galapagos and it is concluded that most of the life on these
former groups is of more ancient origin than in the Galapagos. Geological evi-
dence suggests that during the Eocene there existed between parallels 38 and
45 along what is now the coast of Chile, an extension of the land surface
which probably embraced Juan Fernandez and the Desventuradas. The struc-
ture of the basement rocks of these islands consisting of basalts and tuffs,
also the small degree of erosion and denudation of the islands, do not indicate
an age earlier than Pliocene for these two groups of islands. It is concluded
that the last remnants of Briiggen's "Land of Juan Fernandez" can only have
disappeared finally beneath the sea in very recent times and this supposition
is sufficient to explain the presence of the younger elements of the flora and
fauna on these islands.

The date of the origin of life on the Galapagos is still an open field for
speculation for, while sea bottom soundings have provided no evidence for the
presence of emerged land of any sort between the continent and islands dur-
ing the late Tertiary, the greater part of the Galapagos fauna, if not all of it,
is relatively young.

No. 44) KUSCHEL: GALAPAGOS SYMPOSIUM 95

Literature Cited

Bruggen, J.

1950. Fundamentos de la Geologia de Chile. Santiago, ed. 2, pp. 1-510, il-

lustr. and maps.

Shumway, G.

1954. Carnegie Ridge and Cocos Ridge in the east equatorial Pacific. Jour-

nal of Geology, vol. 62, pp. 573-586.
SKOTTSBERG, C. ED.

1920-1956. History of Juan Fernandez and Easter Island, 3 vols., 688 pp. Upp-
sala, Almquisl & Wiksells Boktryckeri-A.-B.

SKOTTSBERG, C.

1949. Die Flora der Desventuradas Inseln (SanFelix und San Ambrosio), Goete-
borgs Kungl. Vetenskapoch Vitterh els-Sam ha ell esHandlingar-Femte
Foeljden, Ser. B, vol. 6, p. 3-88, 1937. (Spanish edition in Boletin
Museo Nacional de Historia Natural, Santiago, vol. 24, pp. 1-64.

1945. The Juan Fernandez and Desventuradas islands, in Plants and Plant
Science in Latin America, Waltham, Massachusetts, p. 150-153.

1951. Weitere Beitraege zur Flora der Insel San Ambrosio (Islas Desventur-

adas, Chile), Arkiv for Botanik, ser. 2, vol. 1, no. 12, pp. 453-459.
1957. The vegetation of the Juan Fernandez and Desventuradas Islands. Pro-
ceedings of the 8th Pacific Science Congress, vol.4, pp.l81-185»

THE MARINE SHORE-FISHES
OF THE GALAPAGOS ISLANDS*

Richard H. Rosenblatt

Scripps Institution of Oceanography
La Jolla, California

and
Boyd W. Walker

Department of Zoology
University of California
Los Angeles, California

Introduction

The Galapagos Islands have long been of interest to biologists as a na-
tural laboratory for the study of the effects of isolation on the evolution of ter-
restrial organisms. It has perhaps not been so clearly understood that the 650
miles of deep water separating the Galapagos from the South \merican main-
land forms a barrier to the dispersal of shore-dwelling marine organisms as
well. An analysis of the fish fauna indicates that the barrier has been effec-
tive. The material presented here is based on a manuscript checklist of Gal-
apagos fishes, compiled from a critical review of the literature, a re-examin-
ation of much of the previously existing material, and records from recent col-
lections. Owing to the changes necessary, our analysis is quite different
from any based on published lists (Snodgrass and Heller, 1905; Fowler, 1938).

The Environment

The Galapagos Archipelago is a group of oceanic islands, consisting of
13 principal islands and a host of islets and rocks, lying some 650 miles west
of Ecuador. The main portion of the archipelago is located between the equa-
tor and 1°5' South latitude. Two small islands, Culpepper and Wenman, are
separated by some 80 miles from the main body of the group. These, and a
group of three small islands lying some 30 miles from the main group, are sep-
arated from the major islands by deep water. The largest island, Albemarle, is
about 80 miles long by 30 miles wide, but the others are considerably smaller.

• Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science

Association, held at the University of Hawaii, Honolulu, Hawaii, U.S.A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-97-

98 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

The Galapagos are volcanic in origin, and geological opinion seems to
favor the interpretation that they have never been connected with the main-
land. Fossils of Pliocene age have been found, but the group is probably con-
siderably older.

As might be suspected from their volcanic origin, the Galapagos Islands
are characterized by rocky shores, although sand and coral-gravel beaches
are present. The bottom sediments at moderate depths are predominantly coarse.
The Albatross and Velero station records indicate that the bottom is sand,
rocks, or coral at almost all stations. Only once was mud encountered, at 70-
80 fathoms off Daphne Minor Island (Townsend, 1901, Fraser, 1943).
The Galapagos Islands lie in the South Equatorial Current, which is composed
mainly of cold Peru Current water, but with a component of warm water from
the Equatorial Countercurrent to the north (fig. 1). The heterogeneous devia-
tion of the waters bathing the Galapagos causes great variability in tempera-
ture. Differences of 5° C. (Beebe, 1924) and 11° C. (Garth, 1946) have been
reported for the two sides of Albemarle Island. At irregular intervals, the so-
called "El Niiio" years, the Peru Current is deflected far to the west of South
America. Warm water from Central America then sweeps far to the south and
causes extensive warming, causing fish kills along the Peruvian coast. At
these times, the tropical component in the waters surrounding the Galapagos
must be greatly increased (Schott, 1931; Posner, 1957). Fourteen such El Nino
years have been recorded since 1791, the most recent being in 1958.

It is unfortunate that no systematic oceanographic work has been done
at the Galapagos Islands. Little or nothing is known of short- or long-term fluc-
tuations in temperature, and nothing is known of variability from island to is-
land.

Composition of the Fish Fauna

The marine fish fauna of the Galapagos Islands is in large part typical
of the eastern tropical Pacific faunal region, but it is characterized by a high
degree of endemism among the shore species. Twenty-three per cent of the
shore forms are confined to these islands. This endemism, plus significant
elements from the transitional fauna between thePanamic and Chilean faunas,
and from the western Pacific, distinguish the Galapagos fauna as a separate
subunit of the Panamic faunal province.

The fish fauna of the eastern tropical Pacific region (American Pacific
Warm-Water Region of Ekman, 1953) is characterized by a high degree of en-
demism at the species level. With the exception of the circumtropical species
(Briggs, 1961), most of which are pelagic, almost all of the species found in
this area are limited to it.

Owing to the influence ofthe cold Peru and California currents, the ex-
tent of the tropical regions is much curtailed on the western side of the Amer-
icas. The limits of the tropical fauna are at about 25° N. latitude on the outer

No. 44)

ROSENBLATT & WALKER: GALAPAGOS SYMPOSIUM

10=

0°

10=

WINTER

.NORTH EQUATORIAL CURRENT

COST/i
RICA

\TO^I

EQUATORIAL COUNTERCURRENT

^ ^

SOUTH EQUATORIAL CURRENT
GALAPAGOS 'V

PERU

120=

SUMMER

10'

■^EQUATORIAL COUNTERCURRENT J" J

^;A\ t^.. COSTA

RICA

SOUTH EQUATORIAL CURRENT

GALAPAGOS'^'-'

10'

^ %PERU

Figure 1. Current systems in the vicinity of the Galapagos Islands. (After
Schott,1931 and Cromwell and Bennett, 1959).

coast of Baja California and about 5°S. on the Peruvian coast. This is in
marked contrast to the situation in the western Atlantic, where the boundaries
of the tropical region are at about 35° N. and 35° S.

The eastern tropical Pacific fauna is relatively depauperate in compar-
ison with other tropical regions. Probably only the west African fauna is poor-
er (Ekman, 1953, p. 56). This fauna is, however, characterized by a great de-
velopment of fishes characteristic of muddy or sandy bottoms. The families
Engraulididae (anchovies), Ariidae (marine catfishes), and Sciaenidae (croak-
ers) are particularly well developed. In contrast, the fishes primarily adapted

100 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

to coral reefs are very poorly represented. This impoverishment is especially
pronounced in the Labridae (wrasses), Chaetodontidae (butterflyfishes), Scar-
idae (parrotfishes), and Acanthuridae (surgeonfishes).

The relationships of the fishes of the eastern tropical Pacific lie main-
ly with the western Atlantic fauna. A very large number of genera are limited
to the New World tropics. This relationship carries through on a suprageneric
level as well. The blennioid family Chaenopsidae (Stephens, MS) is found on-
ly in this region, as is the trachinoid family Dactyloscopidae (stargazers. In
addition, the atherinid (silverside) subfamily Atherinopsinae (of Jordan and
Hubbs, 1919) is restricted to the New World, as is the gobiesocid (clingfish)
subfamily Gobiesocinae. The clinid subfamily Labrisominae has a similar
distribution, except for two obviously derivative forms found in west Africa,

This basic unity of the American fish fauna (which led Ekman, 1953, p. 30,
to term it the Atlanto-East Pacific Fauna) is due to the presence of a Tertiary
Central American water gap (Durham and Allison, 1960). During the existence
of this connection the faunas on the two sides of the Americas must have been
very similar, although probably not identical. The differences which we see
now are due in large part to differentiation since the destruction of the water
gap, and some migration into the eastern Pacific by Indo-West Pacific species.

The Galapagos ichthyofauna is relatively large as compared with that
of the other oceanic islands of the eastern Pacific. This enrichment is es-
pecially noteworthy in the Serranidae and in certain families that are charac-
teristic of sandy shores, such as the Gerridae, Pomadasyidae, and Sciaenidae.
We record 269 species from 88 families. Seventy-five percent are shore forms
and twenty-five per cent are pelagic or coastal pelagic. The few deep sea
forms that have been taken near the Galapagos Islands are not considered.

Most of the species found on the Galapagos (60 per cent) are found at
other localities in the eastern Pacific, but their ranges do not extend else-
where. By far the largest segment of these (53 percent of the total fauna) are
eastern tropical Pacific endemics, and most are forms ranging widely through-
out the region. This large segment would seem to determine the proper affini-
ties of the fauna. Eight per cent are pantropic. There is small but notable
representation (six per cent of the total fauna) of forms characteristic of the
transitional fauna between the Panamic and Chilean regions. The presence
of these forms indicates the profound effect of the Peru Current on these es-
sentially equatorial islands. Less than two per cent of the species are in
common with the Atlantic and these are also found in other eastern tropical
Pacific localities. Only five species (about two per cent) are found only on
the Galapagos and other eastern tropical Pacific offshore islands.

Endemism

Eighteen per cent of the species are endemic but only one of these (a
flying fish of doubtful validity) is pelagic. The endemism is largely confined

No. 44) ROSENBLATT & WALKER: GALAPAGOS SYMPOSIUM 101

to the shore fishes; twenty-three per cent of these forms are peculiar to the
Galapagos. Further, endemism is not evenly distributed between families.
Over a third of the families with endemic species have two or more such forms.
And the number of endemics does not correlate with the family representation.
The Serranidae (basses) and the Carangidae (jacks) are the largest families;
each has 17 representatives. There are but three endemic serranids, and all
of the carangids have been taken elsewhere. The pomacentrids (demoiselles)
are the next most speciose group with nine representatives, but only one of
these is limited to the Galapagos group. There are seven labrids (wrasses),
but all have been taken elsewhere. On the other hand, three of the five sciae-
nids (croakers) are endemic, as are five of the nine pomadasyids (grunts) and
clinids (klipfishes).

This difference in degree of differentiation correlates with a differen-
tial in vagility. Carangids are strong swimmers, and many live pelagically.
Serranid larvae are well suited to pelagic life (Smith, 1959), and at least some
have special modifications for it. Pomacentrids also have a pelagic prejuven-
ile (Hubbs, 1958) stage in their life history. There is no evidence that the
labrids have a long larval period, but many of the forms are crevice dwellers
and nibblers, and thus would seem eminently suited to rafting.

The sciaenids and pomadasyids are, on the other hand, mostly charac-
teristic of shallow waters in muddy or sandy bays and along open sandy beach-
es. Larvae of these groups are almost never taken in offshore collections, and
very small juveniles are found schooling near the bottom.

Clinids are small, demersal fishes of rocky reefs. The adults are sed-
entary, their eggs are usually demersal, and the larval period is short. Forms
with this type of life history are poor candidates for transport by currents. The
one clinid which seems to be completely undifferentiated (Labrisomus multi-
porosus) has the widest geographic distribution of any Pacific species in the
genus, and also seems to have a longer larval life than is usual for the group
(Hubbs, 1953).

Most of the endemic species of the Galapagos are strongly differentia-
ted from their congeners. It is thus difficult to pinpoint any mainland species
as a sibling or possible ancestor. It is possible, however, to determine the
group (usually generic) to which the Galapagos forms are most closely related.
When the data was analyzed in this fashion we find that of the 46 Galapagos
endemics, 34 are most closely related to eastern tropical Pacific species.
Five are related to forms characteristic of the Peruvian-Chilean warm temper-
ate, two are derived from Indo-West Pacific groups, and one is allied to a
west Atlantic species. The relationships of three were too questionable to in-
clude. This is in general accord with the overall composition of the Galapagos
ichthyofauna.

102 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Analysis of Faunal Relationships

The Galapagos are not particularly close faunistically to the other east-
ern Pacific oceanic islands, Cocos, Clipperton, and the Islas Revillagigedo.
It is true that their faunas have certain common characteristics as opposed to
that of the adjacent mainland areas. They are rich (for this area) in pelagic
types and in Indo-West Pacific species, relatively rich in rocky shore forms,
and poor in sandy shore and muddy bottom forms—that is, they are unbalanced.
In addition the endemics tend to show certain parallel modifications. We do
not feel that these similarities imply any real relationship however. The rela-
tive faunal imbalance reflects two factors. One is the deep water between the
islands and the mainland, which acts as a filter bridge which excludes a large
number of species. The other is the nature of the insular environment, where
deep waters are found close to the shore, and the bottom tends to be mostly
rocky. In the same way the parallel morphological modifications toward more
terete bodies, longer fins, and an increase in number and length of gill-rakers
can be ascribed to adaptation to the island environment.

Snodgrass and Heller (1905) listed seven forms which occurred at two
or more of the islands, and termed them "Eastern Pacific Insular species."
Further collecting indicates that the ranges of four: Prionurus laticlavius,
Melichthys radula, Halichoeres nicholsi, and Lutjanus viridis, extend to the
mainland. Pomacentrus leucorus is restricted to the Revillagigedo Islands
and is replaced at Isla del Coco and the Galapagos by Pomacentrus beebei
(Loren P. Woods, personal communication). Pomacentrus arcifrons and Apogon
atradorsata still are known only from the Galapagos and Isla del Coco.

The presence of these three species on Cocos and the Galapagos indi-
cates that there must have been some faunal transfer in the recent past. It is
almost certain that these species originated on Cocos Island, since transport
is possible only south from Cocos.

The 15 species derived from the warm temperate fauna of Peru and Chile
represent an element not found on the other islands. The presence of these
species and the five endemics with their affinities in this area is related to
the Peru Current which flows from the mainland toward the Galapagos.

Of the 24 Indo-West Pacific forms in the Galapagos fauna (9 per cent)
only two have not been found at other localities in the eastern tropical Paci-
fic. However, one of these is a burrowing eel, otherwise known only from the
type locality, and the other is a pelagic flying fish which likely has a wider
eastern Pacific distribution. Of the remaining 22, 4 are found only on the other
oceanic islands and 18 are found on the mainland as well. Although the abso-
lute numbers of Indo-Pacific forms are about the same at the Galapagos and
the mainland, these species form a more conspicuous element in the depau-
perate Galapagos fauna.

As might be expected, most of these Indo-West Pacific forms are well

No. 44) ROSENBLATT & WALKER: GALAPAGOS SYMPOSIUM 103

adapted to transport by currents. Of the 24 forms, 7 have long pelagic larval
stages and 12 are pelagic as adults as well. Five others are well suited to
rafting, by accompanying floating debris. The two remaining forms are a labrid
(wrasse) and a scarid (parrot fish). Little is known of the early life history
of these groups, but both the young and adults are nibblers and known to
frequent areas of algal growth. Thus they might be good candidates for trans-
port by rafting. These conclusions are in general agreement with those of
Briggs (1961) and Hubbs and Rosenblatt (manuscript).

The evidence indicates that there has been little, if any, direct inva-
sion of the Galapagos Islands from the west. Only two currents impinge on
the Galapagos Islands. The flow of the South Equatorial Current is to the west.
The recently discovered Cromwell Current flows from west to east, but it is
an undercurrent and may well be too deep to be of any use to the larvae or
young of offshore forms (Knauss, 1960, and personal communication). Clipper-
ton and Cocos islands, which are far to the north in the path of the east-flow-
ing Equatorial Countercurrent, have several Indo-Pacific species which have
not been taken elsewhere in the eastern Pacific. If the Cromwell Current were
indeed carrying trans-Pacific migrants, it might be expected that the Galapa-
gos Islands would have a similar number of such forms not found elsewhere.
This expectation is heightened by the prevailing current which flows strongly
away from the mainland. The opposite is, of course, the case. All but two of
the western Pacific migrants found at the Galapagos occur at other eastern
Pacific localities.

The distributional data and the known current patterns in the eastern
Pacific thus indicate that the Galapagos received its Indo-Pacific elements
secondarily from the mainland and Clipperton and Cocos islands. During De-
cember, January, and February there is a southwest flow of water from the
"Panama Bight" into the South Equatorial Current (Cromwell and Bennett,
1959). The possibility for transport would be much greater during El Nino
years, when the flow of warm water from the north is much greater (Schott,
1931; Posner, 1957).

Garth (1946) distinguished a Gulf of California element in the brachy-
uran crab fauna. To explain the uniquely known occurrence at the Galapagos,
and in the Gulf of California, of 11 species of crabs, he found it necessary to
invoke a drastic alteration in the current systems of the Pacific. More recent-
ly (Garth, 1960), this was considered part of a general eastern Pacific island
relationship. As we have indicated earlier, we find no such relationships in
the fishes. Further, we see no reason to expect them. The juggling of ocean
currents to explain distribution patterns is as fraught with hazards as the erec-
tion of land bridges, and should be approached with equal circumspection. It
seems probable that intensive collecting efforts along the mainland coast
would reduce considerably the number of species known only from the Gulf
and the Galapagos.

104 CALIFORNIA ACADEMY OF SCIENCES (Occ Papers

Another concept in need of re-examination is that of the Galapagos ori-
gin of certain Central American species. The burden of Garth's argument was
that a species now occurring at Galapagos and Central America, but without
an Atlantic analogue, must have evolved at the Galapagos. Its absence from
the Atlantic is evidence that it did not invade the Central American mainland
until after the closure of the Central American water gap.

However, the postulate that the western Atlantic and eastern Pacific
had completely common faunas during the existence of a connection between
the Atlantic and Pacific is not compelling. Certainly the connection was a
shallow one, and probably muddy (Schuchert, 1935). Such a connection might
be of little use to a species restricted to the rocky shore habitat. And these
are the species which should be particularly suited to life at the Galapagos,
where rocky habitat predominates.

The fauna of the Gulf of California indicates that continuity of coast-
line in itself does not indicate faunal homogeneity. Certainly the Gulf is in
communication with the rest of the Pacific and yet there are endemic species
of fishes and crabs, and a number of Panamic species are missing (Walker,
1960; Garth, 1960). One could also point to the existence of a large number
of Central American species of fishes which have no Atlantic analogs and
which are not found at the Galapagos or any other oceanic island. If they did
not use the Central American water gap, or if they evolved subsequent to its
closure, may this also not be true of those species which are found at the
Galapagos? This line of reasoning does not prove that the Galapagos have
not been the center of origin of certain Central American species, but we be-
lieve it indicates that the evidence for such an origin is not strong.

Literature Cited

Beebe, William

1924. Galapagos: world's end. G.P.Putnam's Sons, New York, xxi+443 pp.,
frontis, pis. 1-8.

Briggs, John C.

1961. The East Pacific Barrier and the distribution of marine shore fishes.
Evolution, vol. 15, no. 4, pp. 545-554.

Cromwell, T., and E. B. Bennett

1959. Surface drift charts for the Eastern Tropical P acific Ocean. Inter-Amer-
ican Tropical Tuna Commiss ion, Bulletin, vol. 3, no. 5, pp. 217-235
(English): pp. 236-238 (Spanish).

No. 44) ROSENBLATT & WALKER: GALAPAGOS SYMPOSIUM 105

Durham, J. W., and E.G. Allison

I960. The geologic history of Baja California and its marine faunas. System-
atic Zoology, vol. 9, no. 2, pp. 47-91.

Ekman, Sven

1953. Zoogeography of the sea. Sidgwick and Jackson, Ltd., London, xiv +
417 pp.

Fowler, Henry W.

1938. The fishes of the George Vanderbilt South Pacific Expedition, 1937.
Academy of Natural Science of Philadelphia, Monograph no. 2, v +
342 pp., pis. 1-12.

Fraser, C. McLean

1943. General account ofthe scientific work of the Velero III in the eastern
Pacific, 1931-41. Part 111. A ten-year list of the Velero III col-
lecting stations. Allan Hancock Pacific Expeditions, vol. 1, no. 3,
pp. 259-431, charts 1-115.
Garth, John S.

1946. Distribution studies of Galapagos Brachyura. Allan Hancock Pacific
Expeditions, vol. 5, no. 11, pp. 603-638, charts 1-10.

1960. Distribution and affinities of the brachyuran Crustacea. Systematic
Zoology, vol. 9, no. 3, pp. 100-123.

HuBBS, Carl L.

1958. Dikellorhynchus and Kanazawaichthys: nominal fish genera interpreted

as based on prejuveniles of Malacanthus and Antennarius, respec-
tively, Copeia, no. 4, pp. 282-285.

HuBBS, Clark

1953. Revision of the eastern Pacific fishes of the clinid genus Labrisomus.
Zoologica, New York Zoological Society, vol. 3 8, pt. 3, pp. 113-136.

Jordan, D. S., and C. L. Hubbs

1919. Studies in ichthyology: A monographic review of the family Atherinidae
or silversides. Leland Stanford Junior University Publications,
University Series, pp. 1-87, 12 pis.

Knauss, J.

1960. Measurements of the Cromwell Current. Deep Sea Research, vol. 6, no.

4, pp. 265-286.
Posner, G. S.

1957. The Peru Current. Bulletin of the Bingham Oceanographic Collection,

vol. 16, no. 2, pp. 106-155.

Schott, G.

1931. Der Peru-Strom und seine nbrdlichen, Nachbargebie te in normaler und
anorm aler ■ Ausbildung. Annalen der Hydrographie und Marltimen
Meteorologie, vol. 59, pp. 161-169, 200-213, 240-257, pis. 17-22.
Schuchert, C.

1935. Historical geology of the Antillean-Caribbean region or the lands bor-
dering the Gulf of Mexico and the Caribbean Sea. John Wiley, New
York, 811 pp.

Smith, C. L., Jr.

1959. A revision of the American groupers {Epinephelus and related genera).

Microfilm-Xerox copy of Ph.D. thesis. University of Michigan, xiv
+ 563 pp.

106 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Snodgrass, R. E., and E. Heller

1905. Shore fishes of the Re villagigedo, Clipperton, Cocos and Galapagos Is-
lands. Proceedings ofthe Washington Academy of Sciences, vol. 6,
pp. 333-427.

TOWNSEND, C. H.

1901. Dredging and other records ofthe United States Fish Commission Steam-
er Albatross, with bibliography relative to the work of the vessel.
United States Commission of Fish and Fisheries, Commissioners
Report for 1900, pp. 387-562, pi. 1-7.
WALKER, BOYD W.

1960. The distribution and affinities of the marine fish fauna of the Gulf of
California. Systematic Zoology, vol. 9, no. 3, pp. 123-133.

EVOLUTIONARY PATTERNS
IN DARWIN'S FINCHES ♦

Robert I. Bowman

Department of Biology

San Francisco State College

San Francisco, California

Introduction

Darwin's finches of the Galapagos Islands l represent one of the best
known groups of Galapagoan animals. Indeed, they are famous out of all pro-
portion to their size because of their remarkable degree of adaptive radiation
in feeding habits and associated structures — perhaps one of the best exam-
ples of this phenomenon in the class Aves (fig. 1). Furthermore, many of the
species show such an unusual range of variation in structure that to the cas-
ual observer there would seem to be a nearly continuous intergradation of
forms (fig. 2). It was this very fact which greatly impressed the young Charles
Darwin when, in 1835, he first encountered these birds in their native habitat.
In his "Journal of Researches," second edition (1845), he wrote: "Seeing
this gradation and diversity of structure in one small, intimately related group
of birds, one might really fancy that from an original paucity of birds in this
archipelago, one species had been taken and modified for different ends."

Patterns of evolution in Darwin's finches are, fundamentally, adapta-
tions to the environment. In the past it has been customary to explain evolu-
tion as largely or entirely determined by factors of the external environment
acting through selection. Until fairly recently much less attention has been
paid to the inherent properties and potentialities of peculiar genetic systems,
which are the limiting factors of the organism's internal environment (Mayr,
1945; White, 1948). Surely, all evolutionary patterns result from the opportun-
istic interaction of factors of the external environment and genetic systems.

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science
Association, held at the University of Hawaii, Honolulu, Hawaii, U.S. A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

1 One species of Darwin's finch, the honeycreeper-finch (Pinaroloxias inornata), resides only
on Cocos Island, Costa Rica. It is, unquestionably, a member of the Geospizinae subfamily of
fringillid finches. (See Swarth, 1931.)

- 107-

108

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Figure 1. The pattern of adaptive radiation in Darwin's finches.

Figure 2. Variations in shape of bill in 14 species of Geospizinae. A, Geospiza magni-
rostris (Tower Island); B, Geospiza magnirostris (James Island); C, Geospiza conirostris (Hood
Island); D, Geospiza fortis (Albemarle Island); E, Geospiza conirostris (Gardner-near-Hood Is-
land); F, Geospiza foTtis (Chatham Island); G, Geospiza /or//s (Charles Island); H, Geospiza ful-
iginosa (Abingdon Island); I, Geospiza difficilis (Indefatigable Island); J, Certhidea olivacea
(Indefatigable Island); K, Pinaroloxias inornata (Cocos Island); L, Platyspiza crassirostris
(Charles Island); M, Camarhynchus psittacula (James Island); N, Camarhynchus psittacula(Bind-
loe Island); O, Cactospiza pallida (Chatham Island); P, Camarhynchus pauper (Charles Island);
Q, Camarhynchus psittacula (Albemarle Island); R, Camarhynchus parvulus (Indefatigable Is-
land); S, Cactospiza pallida (James Island); T, Geospiza scandens (Abingdon Island); U, Geo-
spiza scandens (James Island); V, Geospiza fuliginosa (Chatham Island), After Swarth, 1931.

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

109

A O

B O

c O

D O

E O

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

In Darwin's finches our study of evolutionary patterns is, necessarily,
restricted in fact to the observable end-products of a long unrecorded history:
There is, of course, considerable basis in theory for a divergence of opinion
regarding the significance of the facts and on the nature and importance of
the biological processes involved; for example, the meaning of intraspecific
variation in bill structure, the importance of the chance factor ("random gen-
etic drift") in accounting for minor interisland differences, and the role of in-
terspecific "competition" in shaping the feeding niches of sympatric "sib-
bling" species. It is not surprising, therefore, that several authors have differed
in their biological interpretation of this remarkable group of birds (Lowe, 1930,
and Stresemann, 1936; Swarth, 1931, and Lack, 1945, 1947; and Bowman, 1961).
We must await the results of many more studies, and especially those of an
ecological and ethological nature, before our understanding of the total biol-
ogy of Darwin's finches is anywhere nearly complete.

The remarks which follow are concerned mainly with the results of evo-
lution; that is, the adaptations by which the Galapagos finches appear to have
"solved" the problems of survival in their particular insular environment.
Some of the views presented here have been discussed more fully elsewhere
(Bowman, 1961).

^^^^--^^^___^ C^^C^

ZONE WIDTH AS A PERCENT

OF TOTAL LENGTH OF TRANSECT

FROM ACADEMY BAY

TO HIGHEST PEAK

ALTITUDINAL LIMITS OF ZONES
ALONG TRANSECT
(IN FEET ABOVE SEA LEVEL)

Figure 3. Altitudinal zonation of the vegetation on the south side of Indefatigable Island,
from Academy Bay to the top. Diagrammatic.

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 111

The Galapagos Environment

Basic to my discussion is an understanding of the Galapagos environ-
ment, about which the following facts are pertinent.

The various islands are remarkably multiform, superficial appearances
to the contrary. They differ in their geologic age (Chubb, 1933), size and ele-
vation, and distance from each other (table 1). The climatic conditions in Gal-
apagos are somewhat anomalous for the tropical Pacific Ocean largely owing
to the modifying effects of the cool Humboldt Current, which surrounds the is-
lands. Whereas there are marked differences in average precipitation both sea-
sonally and yearly, mean daily air temperatures at sea-level vary only two or
three degrees throughout the year (Alpert, 1946).

Correlated with interisland differences in geologic age, climatic expos-
ure, and time of last volcanic activity, are the interisland dissimilarities in
species composition, growth-form, and relative abundance of the vegetation
(table 1), as well as the physical character of the substratum (color, amount
of soil, and mulch).

As is characteristic of most oceanic islands, the flora and fauna are
depauperate in the sense that certain of the typical mainland groups are ab-
sent. With regard to the plants, an individual community is not rich in species,
but because of the local diversity in topography, soil, and moisture, there are
many different plant communities within a single island and between the sev-
eral islands (Howell, 1942; Stewart, 1911, 1915). In response to the climatol-
ogical and pedological features associated with an increase in elevation, there
results an altitudinal zonation of the vegetation on the higher islands. This
phenomenon is most clearly and elaborately demonstrated on the south side of
Indefatigable Island from Academy Bay inland (fig. 3). Close to shore there
is an "Arid Coastal Zone" dominated by cacti, deciduous shrubs, and dwarf
trees (fig. 4); the general aspect is light grey in color, except for a pale green
cast during the rainy season. At slightly higher elevations there is an open
forest growth called the "Transition Zone" (fig. 5); this is a region of inter-
gradation of plants typical of the higher and lower regions. At still greater
elevations a non-deciduous forest prevails, dominated by the tree-composite
Scalesia pedunculata and a dense undergrowth of shrubs (fig. 6). The xero-
phytic nature of the vegetation of the "Scalesia Forest Zone" is most appar-
ent during periods of drought (Svenson, 1946). Above the Scalesia forest two
plant species, Psidium galapageium and Zanthoxylum fagara, retain their tree
stature and constitute the "Brown Zone." Above the Brown Zone on Indefat-
igable Island there occurs a uniqueshrub formation termed the "Miconia Belt,"
about 6 to 10 feet high, composed principally of the fern Pteridium sp. and
the endemic melanostome shrub Miconia robinsoniana (fig. 8). The highest
peaks are treeless and densely vegetated with low growing herbs and ferns,
constituting the "Upland Zone" (fig. 7).

112

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 1. Distribution of 13 species of Geospizinae and comparative data on
16 main islands of the Galapagos Archipelago.

Species

of
Geospizinae

o
-o

E
aj

M
C

o
c

5
a

I-

ttj
a,
a.
u
a

re
0
c

0
0

-a

CO
M

a
c

E
a

C
u
0

3
0

'Ti

c
re
E
c

Geospiza

magnirostris

foTtis

fuliginosa

difficilis

scandens

conirostris

X
X
X
X
X

X
X
X

..f

X
X

••g
X

X
X
X

..c
X

X
X
X

Xh
X

X
X
X
X
X

X
X
X

..d

X
X

..d

Platyspiza
crassirostris

Camarhynchus
psittacula
pauper
parvulus

X
X

X
X
X

..j

• •

X
X

••

X
X

Xk
X

X
X

• •

Cactospiza
pallida
heliobates

■■

X
X

••

..m

• •

••

..n
X

••

Certhidea
olivacea

Total number
of species

per island....

•7

Relative size
of island

(

Highest eleva-
tion (ft.) °

C<1

o
o
in
in

o
in
00

1 — 1

r— 1

0
in
ro
CM

0
in
in

0
in

CO
CM

m
0

0
0

0
m
CO

Vegetation

P
zones

1-3

1-4

1-2

1-4

Total number
vascular
plants

119

329

319

306

103

193

224

Relative size
of flora

Distance from

Indefatigable
Island s

162

. •

139

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 113

One individual collected in September, 1957. Compare with Lack (1945, pp. 9-10) and
Swarth (1931, PP- 146-147).

Compare Swarth (1931, pp. 149-150, 206( and Lack (1945, pp. 8-9).

See Gifford (1919, p. 227) and Swarth (1931, p. 138, 164).

Reported from island but probably not a permanent resident.

^ See Swarth (1931, p. 174).

See Lack (1945, pp. 14-15).

^ See Lack (1945, p. 14).

h , . , .

Now considered extinct.

Numerous individuals collected by author in September, 1957. See alsoGifford (1919, p. 238).

Now considered extinct on this island. See Lack (1945, p. 17), Rothschild and Hartert (1899,
p. 167), and Gifford (1919, p. 246).

The wTiter observed this species on Narborough Island during September, 1957. The only pre-
vious record is that of Snodgrass and Heller (1904, p. 286) based on a single specimen.
Swarth (193L P- 223) refers this specimen to the form "af/inis".

See Gifford (1919, p. 250).

One specimen in collection of the California Academy of Sciences (see Swarth, 1931, p. 249).

See Gifford (1919, p. 254).

Elevations from United States Hydrographic Office Map no. 1798, 11th ed., 1946, except for
Seymour Island.

From Stewart (1911, 1915): 1, dry; 2, transition; 3, moist; 4, grassy.

'^ From Stewart (1911, p. 237).

The smaller the number, the larger (relatively) the flora.

Distances measured in English miles using the American Geographical Society map N.A.-17,
1949 edition.

Darwin's finches reside on all of the main islands of the Galapagos
group, although the number of species represented and their relative abundance
differ from island to island (table 1). In addition to the 13 species of finches,
there is a spotty occurrence of mainland groups of land birds, including the
following resident species: the Yellow Warbler (Dendroica petechia aureola),
the thrasher-like Mockingbirds (four island species of the endemic genus Ne-
somimus), the Martin (Progne modesta), three flycatchers (two species of Py-
Tocephalus and one species of Myiarchus), acuc\ioo(Coccyzus melacoryphus),
and an endemic dove (Nesopelia galapagoensis). Two North American mi-
grants, the Bobolink (Dolichonyx oryzivoms) and the Barn Swallow (Hirundo
erythrogaster), are regular winter visitants to Galapagos (Swarth, 1931).

114

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Figure 4. Vegetation of the Arid Coastal Zone near Academy Bay, Indefatigable Island.
(Photo courtesy R. Freund.)

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

115

Figure 5. Vegetation of the Transition Zone, two miles north of Academy Bay.

116

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Figure 6. Vegetation of the Scalesia Forest Zone, six miles north of Academy Bay.

Figure 7. Vegetation of the Upland Zone, highlands north of Academy Bay. (Photo cour-
tesy R. Freund.)

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 117

Concerning predators on the finches, the following three species of ver-
tebrates are the most important (fig. 9): a hawk (Buteo galapagoensis), the
Short-eared Owl ( Asio galapagoensis), and a colubrid snake (Dromicus biser-
ialis).

Evolutionary Patterns

The major patterns of differentiation in Darwin's finches appear to be
concerned in the main with adaptations for food-getting. Guided by selection,
the exploitation of the constitutional and ecological opportunities has resulted
in an impressive array of food-niche specializations. The adjustments of the
organism to the different ways of feeding have involved not only the basic
feeding mechanism (bill, tongue, palate, jaw muscles, stomach, and intestine)
but also correlated features (plumage, heart, and behavior).

a. Structural pattern in the bill. Darwin's finches are most readily
distinguished on the basis of the relative size and shape of the bill. The 14
species may be grouped into six genera as follows: Geospiza (6 species),
Camarhynchus (3 species), Cactospiza (2 species), Platyspiza (1 species),
Certhidea (1 species), and Pinaroloxias (1 species). Structural features and
mechanical potentialities of the six bill types are summarized in table 2. In
brief, the seed crushing bill of Geospiza, which may be likened to a heavy
duty linesman's pliers (fig. 10), is capable of its greatest adduction at the
base. In Camarhynchus, the bill resembles a high leverage diagonal pliers
with high cutting potential at the tip, and is used to cut into tough woody
tissues wherein insect larvae are to be found. The elongated bill of Cacto-
spiza shows similarities in structure to a pair of long-chain-nose pliers and
serves both for tip-biting and probing while excavating in woody tissues for
insects. The genus Platyspiza is characterized by a bill that basically is
similar to a parrot-head gripping pliers, with crushing potentialities more or
less equally distributed along its length. The bill of Certhidea, somewhat
analagous to a needle-nose pliers, resembles in great detail the bills of cer-
tain parulid warblers, and is suited for probing crevices in search of small in-
sect food. The bill of Pinaroloxias is decurved and slender and resembles
grossly a pair of curved needle-nose pliers. It is well suited for procuring
soft foods such as nectar and insects, and for piercing fleshy fruits.

Species differences in the bills of Geospiza concern the absolute size
and depth-to-length ratio, which features determine the mechanical potential-
ities of the bill. The interspecific differences may more readily be apprecia-
ted if we compare four sympatric species of Geospiza from Indefatigable Is-
land (fig. 11). Especially instructive here is the nature of the individual var-
iation in size of bill in G. fortis, which in its smallest version is but a trifle
larger than G. fuliginosa, and in its largest version only slightly smaller than
G. magnirostris. But despite this impressive size difference within a single

118

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 119

Table 2. Bill features in six genera of Geospizinae.

GENUS BILL CHARACTERISTICS* BILL CAPABILITIES

Geospiza Culmen convex. Strong biting at tip.

Gonys essentially straight. Very strong crushing at base.

Bill large to small, conical elongate.

Camarhynchus Culmen convex (usually strongly so). Very strong biting at tip.

Gonys convex (slightly to strongly). Strong crushing at base.

Bill short, laterally compressed.

Cactospiza Culmen slightly convex. Strong biting at tip.

Gonys slightly convex. Strong probing.

Bill relatively slender.

Platyspiza Culmen strongly convex Very strong crushing along

Gonys straight. entire length.

Bill short, broad, and deep. Very strong biting at tip.

Pinaroloxias Culmen curved. Weak probing.

Gonys straight. Grasping tip.

Bill slender, sharp-pointed, decurved.

Certhidea Culmen straight proximally, slightly Grasping tip.

curved distally. ** Strong probing.

Gonys straight or slightly convex.
Bill small, slender, acute.

* After Swarth, 1931. See fig. 10.
** After Ridgway, 1896 [1897}

population of G. fortis, the same relative shape of bill prevails, as evidenced
by the paralleling of the culmen and gonys in the three sizes of bill.

Within Camarhynchus and Cactospiza, species and individual differen-
ces in the bill involve the absolute size, depth-to-length ratio, and, more
prominently, the curvature of the culmen and gonys. (See fig. 2, and compare
M, N, and Q for Camarhynchus psittacula, and O and S ioT Cactospiza pallida. )

b. Structural pattern in the jaw musculature. The potentialities of
the bills are realized only when the upper and lower mandibles are set in mo-
tion by the jaw muscles. The relative size and position of the muscles affect
the action of the bill. Without entering into a discussion of the kinetics of
the avian bill, or a detailed description of the individual muscles (see Bow-
man, 1961, for details), suffice it to say that within the Geospizinae the great
est variation in the jaw musculature concerns the size of certain of the "ad-
ductor" groups; namely, M. adductor mandihulae extemus and Mm. pterygoi-
deus dorsalis et ventralis (see figs. 12 and 13).

Figure 8. Vegetation of the Miconia Belt, eight miles north of Academy Bay. (Photo cour-
tesy R. Freund.)

120

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

vfvr-r^-M-^^

~ tiWi ; >^ ■

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

121

GEOSPIZA

HEAVY DUTY
LINESMAN'S PLIERS

PLATYSPIZA

PARROT-HEAD
GRIPPING PLIERS

CAMARHYNCHUS

HIGH LEVERAGE
DIAGONAL PLIERS

PINAROLOXIAS

CURVED
NEEDLE NOSE PLIERS

CACTOSPIZA

LONG CHAIN NOSE PLIERS

CERTHIDEA

NEEDLE NOSE PLIERS

Figure 10. Comparison of shapes of bill in six genera of Geospizinae with shapes of six
kinds of pliers (cf. table 2).

To illustrate the nature of the differences, let us consider three sib-
ling species of Geospiza on Indefatigable Island. The large lateral and ven-
tral muscle complexes (nos. 1, 2, 3 and 5, 6, 7, 8, respectively, in figs. 12
and 13) become disproportionately larger as we proceed from the small- to the
medium- to the large-billed species (i.e., G. fuliginosa, G. fortis, G. magni-
Tostris). In parallel fashion we observe a disproportionate increase in size of
these muscles as we proceed from the small- to the large-billed species of
Camarhynchus (fig. 13).

c. The pattern of feeding. On the basis of their diets, the 13 species
of Galapagos finch may be grouped into four categories as follows:

1. Almost exclusively herbivorous: Platyspiza crassirostris

2. Chiefly gramnivorous (with some insects): 6 species of Geospiza

3. Chiefly insectivorous (with some seeds): 3 species of Camarhyn-
chus and 2 species of Cactospiza.

4. Almost exclusively insectivorous: Certhidea olivacea.

Thus there are six different kinds of seed-eating niches occupied by
six species of Camarhynchus , Cactospiza, and Certhidea, in addition to the
herbivore niche occupied by Platyspiza crassirostris.

Figure 9. Three important predators on Galapagos finches. a. Buteo galapagoensis;
b. Asio galapagoensis; c. Dromicus biserialis.

122

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

large magnirostris
small magnirostris

large fort is

culm en

medium fort is

fuliginosa

small for lis

scan dens

gonys

Figure 11. Bill profiles of four species of Geospiza from Indefatigable Island.

A more detailed analysis of the diets and the foraging locations provides
us with important points of difference in the feeding niches. The nine resi-
dent species of finch on Indefatigable Island have been most thoroughly stud-
ied in this regard and data on these are presented in table 3 and figures 14,
15 and 16.

d. Explanation of patterns described. Species of Geospiza represent
several lines of evolution toward the solution of the problem of efficient ex-
ploitation of the seed resources of the Galapagos environment. The great ar-
ray of sparrow-like crushing bills is a clear reflection of the abundance of

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

123

Geospiza magnirostris

Geospiza fortis

Geospiza fuliginosa

Figure 12. Jaw muscles of Geospiza magnirostris, G. fortis, and G. fuliginosa: above,
lateral view of superficial muscles; below, ventral view of superficiar(left half) and deep (right
half) muscles. 1. M. adductor mandibulae externus superficialis; 2. M. adductor mandibulae ex-
ternus medialis; 3. M. adductor mandibulae externus profundus; 4. M. adductor mandibulae pos-
terior; 5. M. pterygoideus dorsalis lateralis; 6. M. pterygoideus dorsalis medialis; 7. M. ptery-
goideus ventralis lateralis; 8, M. pterygoideus ventralis medialis; 9, M. depressor mandibulae;
10, M. pseudotemporalis profundus; 11, M. pseudotemporalis superficialis; 12, M. retractor pal-
atini; 13, Lig. jugomand. art.; 14, Lig. jugomand. ext.; 15, Proc. palato-max.; 16, Proc. transpal.;
17, pterygoid; 18, rhampbotheca.

seeds differing in their size, hardness, and location. A characteristic adapta-
tion of angiosperms in arid and semi-arid regions is a drought-resistant seed
(Stebbins, 1952), which condition is well developed in Galapagos plants (Hook-
er, 1847, pp. 256-257).

The adaptive trends in the Geospiza series proceeding from G. fuligi-
nosa to G. fortis to G. magnirostris are as follows:

Trend

1. more terrestrial in foraging habits

2. consumption of larger seeds

3. consumption of harder seeds

Data presented in
fig. 14
fig. 15
fig. 15

124

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Trend Data presented in

4. consumption of fewer insects fig. 14

5. bill larger and thicker-based fig. 10

6. "adductor" muscles relatively larger fig. 12

Three species of Geospiza; namely, G. difficilis, G. scandens, and G.
conirostns, differ from the foregoing species in having elongated bills; that is,
bills which are longer relative to their basal depth (see fig. 2, I,U,C, respec-
tively). The elongate bill permits the bird to seize food that might be more
difficult to obtain were the bill attenuate, because interference of the eyes
with the substrate is thus substantially diminished. For example, G. scandens
is prone to probe the thick pear-like fruit of Opuntia cactus for moderately
hard seeds, and to insert the bill tip into the spine clusters to procure sugary
secretions at the extra-floral nectaries. In G. conirostric and G. difficilis the
elongated bill permits the birds to reach seeds and insects in crevices and
beneath leaf litter, with a minimum of interference to the eyes.

Platyspiza crassirostris Camarhynchus psittacula Camarhynchus parvulus

Figure 13. Jaw muscles of Platyspiza crassirostris, Camarhynchus psittacula, and Cam-
arhynchus parvulus; above, lateral view of superficial muscles; below, ventral view of super-
ficial muscles; below, ventral view of superficial (left half) and deep (right half) muscles. Num-
bers as in figure 12.

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

125

S I S I S I

FEEDING STATION

C porvuSus

S, 60

S40
2 30
uj20
= 10

®®®
'^ ft

.-^ _^ 1%^

ii Isi

S I S I N I

FEEDING STATION

Plafyspiza

g 60
f^50

IV 40

^30

s 10

Cactospiza

(?.

magnirostns

(? /'or/zs

G fuhginosa

u 60
^50

^40^

2 30 ■:■
? 10 :•;

1- u

_i>:i

C psittacula

r«

1 ■E-i';-

S I S I S L

FEEDING STATION

(^ ground

(B) trunks, large branches

fC) leaves , twigs

1®

S seeds

I insects

fl nectar

L leaves, flowers. seeds

Figure 14. The principal feeding stations and the extent of their occupancy by nine spe-
cies of Geospizinae on Indefatigable Island.

The large-, medium-, and small-billed individuals of Geospiza fortis on
Indefatigable Island (fig. 11) are known to differ in their diets, with the larger
forms taking progressively harder seeds than the smaller forms (see Bowman,
1961, p. 60.

In Camarhynchus, Cactospiza, and Certhidea, the "problem" of extract-
ing insects, which are concealed beneath woody tissues during the daylight
hours to escape from predators and dessication, has been "solved" through
the evolution of powerful tip-biting bills (Camarhynchus), probing bills (Cacto-
spiza), and forceps-like bills (Certhidea).

The adaptive trends in the Camarhynchus series from C. parvulus to C.
psittacula on Indefatigable Island are as follows:

Trend Data presented in

1. more arboreal in foraging habits fig. 14

2. consumption of larger insects larvae fig. 16

3. consumption of fewer seeds fig. 14

126

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Trend Data presented in

4. bill larger and thicker fig. 13

5. "adductor" muscles relatively larger fig. 13

If we compare all the "insectivorous" finches on Indefatigable Island
in the sequence Certhidea olivacea--Camarhynchus parvulus—Camarhynchus
psittacula--Cactospiza pallida, we find that the smaller-billed species feed
on smaller insects (larvae) than do the larger-billed species (fig. 16.) Concom-
itantly, Certhidea ioTSiges typically on the leaves and terminal twigs of bushes
and trees, whereas the larger-billed and smaller-billed species of Camarhyn-
c>?>ws forage typically on the larger and smaller branches of trees, respectively,
with Cactospiza showing a distinct preference for large branches and trunks
in its search for insect booty (see fig. 14).

Geospiza fuliginosa

Geospiza scandens

Geospiza forfis

Geospiza magnirostris

A B C D E F G H I
SIZE OF SEED

Geospiza fuliginosa

A B C D E

SEED HARDNESS

Geospizo scandens

Geospiza fortis

Geospiza mognirostris

Figure 15. Analysis of the diets of four species of Geospiza from Indefatigable Island
on the basis of size (above) and hardness (below) of seeds consumed.

e. Structural pattern in the digestive tract. Invertebrates, general-
ly, it is well known that herbivorous species possess relatively longer intest-
ines than do carnivorous and nectivorous species— a condition correlated with
the greater east of digestion and assimilation of proteins and simple sugars
as compared to starches and celluloses. A trend of this kind may be demon-
strated in species of Galapagos finches on Indefatigable Island (fig. 17) by
comparing the relative lengths of the intestine (i.e., length of intestine over
cube root of body weight) with the relative amounts of cellulose-rich food in
the diets.

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

127

Certhtdea olrvacea

A B C 0

SIZE OF LARVA

Camorhynchus porvulus

Comarhynchus psittaculo

Cactospizo pallido

Figure 16. Analysis of the diets of four species of insectivorous finches from Indefati-
gable Island on the basis of size of larvae consumed.

Whereas the gradual shortening of the intestine in the morphological
series Geospiza magnirostris--G. fortis—G. fuliginosa is correlated with a re-
duction in starch- and cellulose-rich seeds and an increase in protein-rich in-
sects (fig. 14), in G. scandens the still shorter intestine is correlated with a
seed diet supplemented with sugar-rich nectar and comparatively more insects.
The intestine of Platyspiza is conspicuously longer than that of Geospiza
magnirostris owing to the fact that the former species consumes, in addition
to seeds, large quantities of buds, leaves, and flowers, which items are taken
much less frequently by the latter species. Platyspiza rarely feeds on insects.

In the insectivorous series of finches; namely, Camarhynchus parvulus—
C. psittacula--Cactospiza pallida-- Certhidea olivacea, there is a regular re-
duction in the relative amounts of plant food in the diets, tending toward com-
plete insectivorousness in Certhidea. Correlated with this shift in diet is the
gradual reduction in length of intestine (see also fig. 14).

f. Foraging activity and heart size. Recent studies by Hartman (1954,
1955) and Norris and Williamson (1955) have shown, among other things, that
species differences in heart weight may be a reflection of certain inherent
physiological adaptations, and particularly as this relates to activity. It has
been assumed that in any one species a particular heart size is an adaptation
of the circulatory system to the sum total of the various physiological condi-
tions resulting from physical exertion, heat production, and environmental in-
fluences. Since the major differences between species of Galapagos finches
concern adaptations for food-getting, and since food-getting constitutes a major
part of the daytime activity of the birds, some correlation between heart size
and type of foraging activity might be expected.

Platyspiza crassirostris, the largest (heaviest) finch, has the smallest
heart ratio (table 4). Correlated with this is the fact that Platyspiza is most
commonly seen sitting quietly in bushes or trees feeding on berries, leaf buds,
or flowers. Platyspiza show less activity in food-getting than does any other
species of finch.

128

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Table 3- Food habits of the Geospizinae,

P^CJOD HABITS OF GEMS

FOOD HABITS OF SPFCIFS

SPECIES UITH SIMILAR BILL

Geospiza: mainly seeds, and

magnirostris; small variety of

Coccothraustes coccothraustes

occasionally exposed
insects.

hard seeds

( Fringillidae)

fortis: large variety of moder-

Melanospiza richardsoni

ately hard seeds

(Fringillidae)

fuliginosa: large variety of

Passerina cyanea

soft seeds

(Fringillidae)

scandens: small variety of

Tangavius aeneus

moderately hard seeds; pref-

(Icteridae)

erences for fruits and nectar

of Opuntia cactus

difficilist poorly known but

Lophosphingus griseo-cristatus

presumably similar to fuli-

(Fringillidae)

ginosa, but possibly includ-

ing more insects

conirostris: poorly known but

Saltator albicollis

presumably soft to hard

(Fringillidae)

seeds and soft tissues of

Opuntia cactus

Camarhynckius: mainly con-

psiltacula: moderate variety of

Psittiparus gularis

cealed insects excavated

largish insects; fewsoft seeds

( Paradoxornithidae)

from woody tissues, and
occasionally seeds

pauper: poorly known, but pre-

Similar to above

sumably intermediate between

psiltacula and parvulus

parvulus: large variety of

Parus inornata

smallish insects and moder-

(Paridae)

ate amount oi soft seeds

Cactospiza: mainly conceal-

pallida: small variety of larg-

Tachyphonus coronatus

ed insects removed by
furrowing with bill and by

ish insects; soft fruits

(Traupidae)

means of a "tool" held in

heliobates: poorly known but

Similar to above

bill {pallida only); occa-

presumably mainly insects

sionally soft fruits and

from mangroves

seeds

Platyspiza: buds, leaves,

crassirostris: same as for

Structural equivalent not known

flowers, fleshy fruits, soft

genus

to hard seeds

Certhidea; insects exclus-

olivacea; same as for genus

Basileuterus belli

ively, and mainly small

(Parulidae)

exposed forms

Pinaroloxiasr presumably

inornata: same as for genus

Coereba flaveola

insects, nectar, and

("Coerebidae")

some fruit

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

129

LjJ

CO
LU

U.
O

I-
z

LlI
>

1 —

1 1

n 1 r-

1 1

80 -

70 ■

•

no"*

,x-

60 •

•

.^^

50 ■
40 •

C5-

0)-

30 •

1—

— 1 1

H 1 1-

— 1 1

10 20 30 40 50 60 70 80 90

PERCENTAGE OF CELLULOSE-RICH FOOD IN DIET

Figure 17. Relationship between intestinal length and diet in nine species of Geospizinae
from Indefatigable Island.

Camarhynchus psittacula and C. parvulus have very similar methods of
foraging, but there are some fairly obvious differences. In general, C parvulus
forages on the small branches and terminal twigs of trees and bushes, where
its behavior resembles that of certain parids. The larger C. psittacula tends
to forage more on the larger branches of trees, where its twisting actions with
the bill appear to be more vigorous than similar actions in the smaller C par-
vulus, and undoubtedly of greater absolute strength. In other words, the field
observations do not indicate any important differences in intensity of foraging
activity, but do demonstrate certain significant differences in habitat selec-
tion. The difference in heart ratio between C parvulus (.664) and C. psitta-
cula (.632) is prohahly the result oi the diiierences in general body size (fig. 18).

Certhidea olivacea is not only the smallest but also the most active of
the Galapagos finches. Its relatively large heart (largest heart ratio) is surely
a reflection of this high level of activity. Its erratic aerial flights, frequent
wing flitting, and constant changing of position while foraging in the foliage,
are all manifestations of its relatively greater metabolic rate. Certhidea is al-
most the perfect antithesis of Platyspiza with regard to activity and relative
heart size.

130

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

8 9 10 15 20 25 30 35

BODY WEIGHT IN GRAMS

Figure 18. Average heart weight plotted against average body weight for nine species of
Galapagos finches from Indefatigable Island (Logarithmic scale.)

Cactospiza pallida and Geospiza scandens have the same heart ratio
(.690), which value is second largest in the group (table 4). Not only do these
two species have the same body size and superficially similar bills (fig. 1),
but also both may forage on the Opuntia cactus. Because of these similarities,
both were considered originally to be members of the same genus ("Cactomis").
The practice of foraging on the trunks of trees (or cactus) requires an excep-
tionally high expenditure of energy, merely in maintaining ahold, let alone in
climbing about or in excavating with the bill. This might account for the rela-
tively large and identical heart ratio for these species.

The three species of "ground-finch," Geospiza magnirostris, G. fortis,
and G. fuliginosa, have heart ratios of .674, .647, and .594, respectively. This
series constitutes a major exception to the general principle that smaller birds
have relatively larger hearts than do larger birds (Hartman, 1955, p. 223). In

No. 44)

BOWMAN: GALAPAGOS SYMPOSIUM

131

Table 4. Heart ratio for nine species of Galapagos finches from
Indefatigable Island,

SPECIES

HEART RATIO*

SPECIES

HEART RATIO*

Geospiza

magnirostris

fort is

fuliginosa ....
scandens

Cactospiza
pallida ...

.674
.647
.594
.690

.690

Cer thidea
olivacea..

Camarhynchus
parvulus ....
psittacula ..

Platyspiza

crassirosiris

.697

.664

.632

.538

* Mean heart weight expressed as a per cent of mean body weight

attempting to account for the differences, it should first be pointed out that
all three species spend about 50 per cent of their time foraging at ground level
where scratching with the feet in search of seeds demands the greatest phys-
ical exertion of any foraging activity typical of these three species. Field ob-
servations indicate that G. magnirostris is somewhat more wary than the two
smaller species, and head movements are much slower and more deliberate in
G. magnirostris. The latter face prompted me to examine the relative size and
weight of the head in these three species. Whereas in all finches other than
G. magnirostris, G. fortis, and G. fuliginosa, the skull and lower jaw make up
23 to 34 percent of the total skeletal weight, in the three species of Geospiza
under consideration the skull and lower jaw comprise 46.8, 38.9, and 27.8 per
cent, respectively, of the total skeletal weight.

In view of these rather striking differences in head size, it would seem
to be reasonable to imagine that the differences in heart ratio between the lar-
ger and smaller species oiGeospiza(G. scawfiews excepted) might be correlated,
at least in part, with the relatively greater energy demands for the function-
ing of the very large jaw musculature, and also for maintaining the posture of
a much heavier head (see fig. 12). The differences in the heart ratios between
Geospiza magnirostris, G. fortis, and G. fuliginosa are attributed mainly to
differences in the relative size differences in the skull and jaw musculature.

Observations on the flight of species of Geospiza in the wild and in cap-
tivity indicate that G. scandens has the strongest and most rapid flight as
well as the greatest agility, whereas G. fuliginosa has the weakest type of
flight. It is probably not fortuitous that, of the four species of Geospiza on
Indefatigable Island, G. scandens has the largest and G. fuliginosa the small-
est heart ratio.

132

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

100

111

-^ INSECTIVOROUS

ABOVE GROUND FORAGING

!'■ ■ i I y ■'■'*■ I ■ ■ ■
••■■■■■■•■■•■

lasaaaaflaaaaB

aaaaaaaaaaaaa

-----^aaaaaea

- - - - a a a

:•:•:■:• ground level foraging :•:•:•:■:■:■:•:

• a ■ ■ ■ ■ ■ ari
■ ■••••■-
■ ■ a a a ■ I

I a • a I
a a a a
I a a a L,
a ■ ■ aji

• a a a a a ■
a a ■ a a a r

a ■ a a a a
a • ■ a a a L

a • a a a a ■
a a a a a a ~

■ ■ ■ ■ iti'n i'l ■■■ i

laaaaaaaaaaaa
aaaaaaaaaaaa
laaaaaaaaaaaa

GEOSPIZA PLATYSPIZA CAMARHYNCHUS

CACTOSPIZA

CERTHIDEA

<
2

V%l^t^T

® ® ! ® © ® ®

Figure 19. Correlation of male plumage condition, foraging level, and diet in five genera
of Geospizinae.

g. Adaptive variation in plumage and bill.

(1) Plumage coloration. Most previous workers on the finches have
claimed that the plumage colorations are of little or no adaptive value. I do
not believe that the available evidence supports this view.

Because of the dietary differences between the finch species, it is not
surprising that we should find differences in foraging level (fig. 14). For ex-
ample, the seed-eaters of the genus Geospiza spend about 50 percent of their
time on the ground in search of seeds. In the arid coastal zone, where these
species are most common, there is a preponderance of dark colored lava. Cor-
related with these conditions of behavior and environment are the adult male
plumages that may be fully black, partially black, or non-black and essential-
ly like that of the females (fig. 19).

The insect-eaters of the genus Camarhynchus, as well as the fruit-and-
bud eaters of the genus Platyspiza, find their food chiefly on the branches and

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 133

among the foliage of trees and shrubs where the dominant colors are green and
grey. Occasionally the birds will forage for seeds on the ground. Thus, these
birds, Camarhynchus and Platyspiza are brought into contact with backgrounds
of strong color contrast, namely, grey-green and black. The plumages of the
adult males of Camarhynchus and Platyspiza are usually black over head and
breast, black on the head only, or completely grey brown like the females
(fig. 19). Those individuals with black on the anterior parts of the body are
surprisingly difficult to see either on the ground or in the trees, because of
the visually disruptive effect produced by this kind of marking.

The remaining species of finches of the genera Cactospiza and Certhi-
dea rarely forage at ground level. Their plumages are various shades of olive
and grey, but never black, thus matching the dominant hues in the trees and
shrubs where they forage.

The selective force in the case of plumage coloration is predation by
hawks, owls, and snakes (fig. 9).

There are numerous examples of geographic variation in plumage color-
ation in the Galapagos finches. The most striking of these is to be found in
the genus Geospiza. In this group there may be a succession of plumages in
the male beginning with no black, followed by increasing amounts of black
over head and breast, to complete blackness (see fig. 19). This gradual de-
velopment is at least partly associated with age. At each annual molt an in-
creasing number of black feathers may appear, but in addition there are some
plumage types that are genetically fixed. Some birds may appear to acquire a
partially black plumage precociously, and retain this stage in subsequent years.
Other males never seem to acquire any black plumage whatsoever. Further-
more, the relative frequency of the various plumage types in adult males seems
to be somewhat different from island to island (Lack, 1945; Swarth, 1931), al-
though an intensive field study of this situation is still wanting. Because
there are differences in the dominant background color between islands, we
may assume that each plumage type has its own selective advantage in cer-
tain kinds of environments, and that the specific frequency of occurrence of
each type may change from season to season, depending upon the age compo-
sition and sex ratio of the population, as well as upon the local feeding hab-
its of the birds. In other words, the non-black, the partially black, and the
fully black male plumages adapt the population as a whole to the extremes of
background coloration. The need for such camouflage is greatest at the end of
the dry season in the arid coastal zone.

(2) Bill structure. It seems clear that a species living on two islands,
differing in their food supply, is going to show geographic variation in its
feeding harits. And such is known to be the case on Galapagos. Let me illus-
trate this point with one example. The bill of the grosbeak-finch (Geospiza
magnirostris) from Tower Island is almost the largest for the species; on In-

134

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

defatigable Island the bill is of somewhat smaller size. An examination of the
skulls from both islands shows that there are differences in the overall rug-
gedness, in the size of processes for muscle attachment, and in relationships
of bones of the skull (fig. 20). The functional significance of these inter-is-
land differences in morphology may be summarized as follows: the finches on
Tower Island are capable of more powerful adduction than the finches on In-
defatigable Island. Indeed, on Tower Island relatively more of the available
seeds are large in size and hard shelled, than are those on Indefatigable Is-
land, to judge from the known facts about the vegetation on the two islands.
The anatomical differences in the head region between these two island pop-
ulations of Geospiza magnirostris are of the same general character as those

Tower Island

Indefatigable Island

Figure 20. Comparison of the skulls of Geospiza magnirostris from Tower and Indefatig-
able islands in lateral profile (left) and posterior profile (right).

differences between large-, medium-, and small-billed individuals oi Geospiza
fortis (fig. 11), about whose functional significance there is no doubt. Addi-
tional examples are discussed elsewhere (Bowman, 1961).

Adaptive Radiation in Darwin's Finches

Within this one insular sub-familial group of songbirds, the Geospizinae,
we find biological equivalents of no less than seven continental familial groups,
(see fig. 1). This pattern of adaptive radiation has been shaped largely by the
nature of the Galapagos environment and by the genetic constitution of the birds.

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 135

Origin of the Geospizinae. Although Galapagos probably has been in
existence since Tertiary times (Shumway, 1954), we have no notion as to the
exact time of entry by the ancestors of the finches, or of any other terrestrial
group. There seems to be little doubt that the Galapagos (and Cocos) islands
are truly "oceanic" in origin inasmuch as they are composed almost entirely
of basaltic lava, and the deeps between the archipelago and the mainland are
so great as to preclude a former continuous land connection (see Shumway,
1954). The general inaccessibility (or unsuitability) of the islands to terres-
trial colonists from the adjacent mainland of South America is indicated by
the seemingly random make-up of the biota, especially well seen in the fam-
ilies of vascular plants and insects (Hooker, 1847; and Van Dyke, 1953).

In view of the remarkable uniformity in the internal anatomy, plumage,
song, nest, and egg in the 14 species of Geospizinae, it is reasonably certain
that Darwin's finches constitute a monophyletic group of birds. But the pre-
cise nature of the ancestral type is not quite so obvious as some writers would
seem to think (see Simpson, et al., 1957, p. 446). Avian systematists are of
the opinion that several New World families of songbirds are phylogenetically
closely related, including the sparrows (Fringillidae), thetroupials (Icteridae),
the tanagers (Thraupidae), the warblers (Parulidae), and the honeycreepers
(Coerebidae). I think it is significant, therefore, that we find among Darwin's
finches ecological and morphological counterparts of these mainland families
(see fig. 1). And in addition, we find equivalents of two other mainland fami-
lies, the parrotbills (Paradoxornithidae) and the titmice (Paridae), which are
not generally considered to be closely allied to the previously mentioned
groups.

Since only five of the 14 species of Geospizinae are clearly identifiable
as "finch" types, I see no reason to assume a priori that a "finch" origin of
the group is any more likely than a "warbler" origin, etc. (see table 3). Also,
we are not obliged to assume that the geospizine ancestors came from the ad-
jacent coast of South America (Ecuador) simply because that region is the most
proximate. To the evidence marshalled by Swarth (1934), showing a close af-
finity between elements of the Galapagos and Caribbean avifaunae, may be
added the example of Geospiza fortis, which shows a striking resemblance to
Melanospiza richardsoni of St. Lucia Island, Lesser Antilles. The Galapagos
may have been no less remote in effect to colonists from the Caribbean than
from coastal Ecuador when one considers the possibility of chance rafting in
mid-Tertiary times by means of an ocean current system flowing through breach-
es in the Isthmus of Panama (Swarth, 1934; Vinton, 1951).

In summary it may be said that we have no precise notion about the na-
ture of the ancestors of the Geospizinae; nor do we know the place of origin
of the colonial stock other than that it was from America.

136 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Conditions on the Galapagos Islands in Colonial times. We can only
speculate on the environmental conditions as they existed when the ancestors
of Darwin's finches arrived in the Galapagos Archipelago. It would appear to
this writer, however, that there is little justification for the unilateral assump-
tion that once the ancestral geospizines gained access to the islands, they
entered into a land of remarkable ecological opportunity (Simpson, etal., 1957,
p. 445), of abundant foods and varied living quarters, unmarred by the presence
of competitive neighbors, and with complete freedom from enemies (Lack, 1947,
p. 114). It is just as likely, I believe, that ecological opportunity was very
limited when the ancestors of Darwin's finches first arrived in their newly
found environment, and that they evolved together with the floral and other
faunal elements of Galapagos, including the predators.

The various islands appear to be of different geological age (Chubb,
1933), which means that the number of islands, their size and height above
sea level, probably were different at various times in the past. Present-day
differences in the flora and fauna of the islands— islands in some cases sep-
arated by only a few miles of ocean— are, indeed, striking (see table 1), and
surely are a reflection of differences which existed to a greater or lesser ex-
tent in the past.

Constitutional make-up of the geospizine ancestors. Whether the or-
iginal colonization of Galapagos included many or few individuals, or if there
was more than one invasion by the ancestral type, we shall never know. Lack
of information on these and other matters makes it difficult to assess the ef-
fect of random genetic drift in the evolution of the Geospizinae. To be sure,
the degree of heterozygosity in the genetic environment of the founding fore-
bears was determined by the number of the invading colonists and their indi-
vidual hereditary constitution. If we assume that the founders were few in
number and derived entirely from a genetically depauperate "peripheral" main-
land population, then one may envision some form of disharmony in the genetic
environment of the colonists (Mayr, 1954). The effects of a "genetic bottle-
neck" may have been manifest at several times subsequent to the initial col-
onization. For example, interisland invasions, volcanic eruptions, and period-
ic droughts are some of the possible causes of major population reductions.

The most favorable structure for rapid evolution is that of a large or
medium sized population divided into many small sub-units or colonies which
are largely isolated from each other, but can interchange genes through occa-
sional migration between them (Wright, 1940). Such a population permits new
gene combinations to become established in the individual sub-units both
through natural selection ("anti-chance" factor) and through random genetic
drift ("chance factor"), without the swamping effect which occurs in large
populations. At the same time, migration between colonies prevents their stag-
nation, and allows the population as a whole to draw upon a large supply of
genes (Stebbins, 1952, p. 35).

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 137

One might ask, is it possible to distinguish the results of natural se-
lection from those of random genetic drift? What criteria are we to use? In
order for two small insular populations to drift apart genetically, there must
be identical, or very similar, environmental conditions on the two islands. At
the present time we know that selection pressures on the finches differ in kind
and degree from island to island as a consequence of differences in food sup-
ply (seeds, insects) and predation pressure (hawks, owls, snakes), and it is
reasonable to think that such differences have existed to a greater or lesser
extent in the past.

All the structural and behavioral features of the Geospizinae studied up
to now have an adaptive explanation. Even certain minor inter-populational
differences in plumage coloration and bill dimensions can reasonably be ex-
plained by selection; there is no need to invoke chance factors. This is not
to say that random genetic drift did not play some role in the evolution of the
Geospizinae through interaction with selection, but rather, that convincing
evidence has not yet been marshalled in support of it.

The constitutional limitations of the founders of Darwin's finches are
suggested by the apparent gaps in the picture of adaptive radiation. For ex-
ample, genetic factors (other than "Sewall Wright effect") might explain the
absence of "lark-finches" and "shrike-finches" in the geospizines, since
alaudids and laniids are not closely related to the "parulid-thraupid-icterid-
coerebid-fringillid" complex, to which the geospizines seem to be allied. It
is likely that the lark and shrike niches are available on certain of the larger
and higher islands of Galapagos. It might be suggested that the absence of a
specialized nectar feeder ("honeycreeper-finch") on the Galapagos is due to
the genetic inability of the Geospizinae to evolve in that direction. But this
appears not to be the case. Rather, on Galapagos there is no continuous and
plentiful supply of nectar to support this kind of feeder, in contrast to condi-
tions on Cocos Island where a "honeycreeper-finch" (Pinaroloxias inornata)
has evolved in a lush tropical rain forest.

We should hardly expect the geospizines to have given rise to "mock-
ingbird-finches", "swallow-finches", "flycatcher-finches", and "cuckoo-
finches" since had mockingbirds, swallows, etc. , been neighbors of the newly
evolving geospizines, these niches would have been occupied and unavail-
able for exploitation by the geospizines. Also, it should be noted that these
mainland types are, presumably, remotely related to the ancestral geospizine
stock, and therefore we may suppose that even if the mainland mockingbirds,
swallows, etc. were absent from Galapagos, geospizine counterparts might
not have evolved. With unlimited ecological opportunity, time and the consti-
tutional make-up of the geospizine ancestors are the over-riding restrictions
shaping the evolutionary destiny of the finches.

The pre-adaptational potential of the ancestral geospizines was consid-
erable, to judge from the results of adaptive radiation that we see today (fig.

138 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

1). This genetic potential was released in the insular environment of Galapa-
gos where rather sudden changes in the feeding mechanism and associated be-
havior were necessitated by frequent shifts in the conditions of the environ-
ment resulting from repeated inter-island invasions. One character, possibly
of a pre-adaptive nature, occurring in all geospizines and also in several close-
ly related mainland groups, is the presence of partially pneumatized window
areas in the cranial vault. These stress-resistant regions may have permitted
more rapid readjustments in the head than would otherwise have been possible,
as new feeding opportunities became available (Bowman, 1961, p. 261).

The origin of new species of Galapagos finches. When the ancestral
geospizines arrived in Galapagos, they were confronted with an environment
different in most of its ecological aspects (food resources, competitive neigh-
bors, and the like) from the one just vacated. Following the original estab-
lishment of a colony on one of the islands, the birds soon moved about the ar-
chipelago establishing footholds on other islands. During such periods of
population dispersal, the birds were confronted with somewhat different food
conditions (among other things), and being more or less isolated by ocean from
other populations, island ecotypes soon evolved. Ultimately, selection piled
up sufficient genetic differences so that when the incipient species on island
"A" (where it had evolved) moved to island "B," it remained reproductive ly
isolated from all other closely related birds present, and thereafter behaved
as a full species. In this manner the various species of Geospizinae were
probably evolved.

Island races of the same species are a reflection of subtle inter-island
differences in feeding niches. For example, the Geospizamagnirostris "format"
might have been evolved on an island where large hard seeds were the primary
food available. Once this basic grosbeak bill appeared, its size could be
further modified by selection to better accomodate the slightly different-sized
hard seeds prevailing on other islands, thus effecting the most efficient bill-
mechanism commensurate with the available food resources.

Conclusion

The patterns of evolution discussed above are largely concerned with
biological adjustments in Darwin's finches to their food plants and animals
(such as powerful bills for crushing hard seeds and cutting into tough woody
tissues)! to predators (such as plumage coloration for concealment), and to
the physical environment (such as relatively small hearts in response to warm
and constant air temperatures). Each pattern involved not only the whole or-
ganism, but the organism plus its environment. It is the totality of these func-
tional systems that has been subjected to selection.

No. 44) BOWMAN: GALAPAGOS SYMPOSIUM 139

Literature Cited
Alpert, L.

1946. Notes on the weather and climate of Seymour Island, Galapagos Archi-

pelago. Bulletin of the American Meteorological Society, vol. 27,
pp. 200-209.

BOWMAN, R. I.

1961. Morphological differentiation and adaptation in the Galapagos finches.
University of California Publications in Zoology, vol.58, pp. 1-VII,
1-302.
Chubb, L. J.

1933. Geology of Galapagos, Cocos, and Easter islands. Bernice P. Bishop
Museum Bulletin, p. 110.

DARWIN, C.

1845. Journal of researches into the natural history and geology of the coun-
tries visited during the voyage of H.M.S. Beagle round the world,
under the command of Capt. FitzRoy, R. N., 2d rev. ed.; London;
John Murray.
GIFFORD, E. W.

1919. Field notes on the land birds of the Galapagos Islands and of Cocos
Island, Costa Rica. Proceedings of the California Academy of Sci-
ences, ser. 4, vol. 21, pp. 189-258.

Hartman, F. a.

1954. Cardiac and pectoral muscles of trochilids. Auk, vol. 72, pp. 267-469.

1955. Heart weights in birds. Condor, vol. 57, pp. 221-238.

Hooker, J. D.

1847. On the vegetation of the Galapagos Archipelago, as compared with that
of some other tropical islands and of the continent of America.
Transactions of the Linnaean Society, vol. 20, pp. 235-262.

Howell, J. T.

1942. Up under the equator. Sierra Club Bulletin, vol. 27, pp. 79-82.

Lack, D.

1945. The Galapagos finches (Geo spizinae ): A study in variation. Occasional
Papers of the California Academy of Sciences,, no. 21, pp. 1-159.

1947. Darwin's finches. Cambridge University Press. 208 pp.

Lowe, P. R.

1930. Hybridisation in birds in its possible relation to the evolution of the
species. Bulletin of the British Ornithological Club, vol. 50, pp. 22-29.

MAYR, E.

1954. Change of genetic environment and evolution. In, Evolution as a process,

pp. 157-180; Editors: J. Huxley, A. C. Hardy, E. B. Ford; London:
George Allen and Unwin.

NORRis, R. A., AND F.S.L. Williamson

1955. Variation and relative heart size of certain passerines with increase in

altitude. Wilson Bulletin, vol. 67, pp. 78-83.

RIDGWAY, R.

1896 [T897]. Birds of the Galapagos Archipelago. Proceedings of the U.nited
States National Museum, vol. 19, pp. 459-670.

140 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Rothschild, W., and E. Hartert

1899. A review of the ornithology of the Galapagos Islands. With notes on
the Webster-H arris expedition. Novites Zoologicae, vol. 6, pp. 85-205.

Shumway, G.

1954. Carnegie Ridge and Cocos Ridge in the east equatorial Pacific. Jour-
nal of Geology, vol. 62, pp. 573-586.

Simpson, G. G., C S. Pittendrigh, and L. H. Tiffany

1957. Life: an introduction to biology. New York: Harcourt, Brace and Co.
845 pp.

Snodgrass, R. E., and E. Heller

1904. Papers from the Hopkins-Stanford Galapagos expedition, 1898-1899.

XVI. Birds. Proceedings of the Washington Academy of Sciences,

vol. 5, pp. 231-372.
Stebbins, G. L.

1952. Aridity as a stimulus to plant evolution. American Naturalist, vol. 86,

pp. 33-44.
Stewart, A.

1911. A botanical survey of the Galapagos Islands, Proceedings of the Cali-
fornia Academy of Sciences, ser. 4, vol. 1, pp. 7-288.

1915. Some observations concerning the botanical conditions on the Galapa-
gos Islands. Transactions of the Wisconsin Academy of Sciences,
Arts and Letters, vol. 18, pp. 272-340.

Stresemann, E.

1936. Z ur Frage der Artibildung in der Gattung Geospiza. Orgaan der Club
van Nederlandische Vogelkundigan, vol. 9, pp. 13-21.

SVENSON, H. K.

1946. Vegetation of the coast of Ecuador and Peru and its relation to the Ga-
lap a-gos Archipelago. American Journal of Botany, vol.33, pp. 394-
426.

Swarth, H. S.

1931. The avifauna of the Galapagos Islands. Occasional Papers of the Cali-
fornia Academy of Sciences, no. 18, pp. 1-299.

1934. The bird fauna of the Galapagos Islands in relation to species forma-
tion. Biological Reviews, vol. 9, pp. 213-234.

VAN Dyke, E.G.

1953. The Coleoptera of the Galapagos Islands. Occasional Papers of the

California Academy of Sciences, no. 22, pp. 1-181.

Vinton, K. W.

1951. Origin of life on the Galapagos Islands. American Journal of Science,
vol. 249, pp. 356-376.

White, M. J. D.

1948. Animal cytology and evolution. Cambridge University Press.

Wright, S.

1940. Breeding structures of populations in relation to speciation. American
Naturalist, vol. 74, pp. 232-248.

PROTECTION AND

CONSERVATION PROBLEMS

ON THE GALAPAGOS ISLANDS*

Misael Acosta-Solfs

Instituto Ecuatoriano de Ciencias Naturales
Quito, Ecuador

The Galapagos Archipelago is a jewel of nature which, after Darwin's
studies in 1859, has attracted the attention of scientists the world over.

In 1934 several sections of Galapagos were declared an official reserve.
At that time, the Government of Ecuador authorized a survey by the engineer
Frederick Paez. He was encouraged by a group of professors at the Ecuador-
ian Central University, and by many other persons fond of nature, including
the learned professor Jonah Guerrero.

Unfortunately, the executive decree of 1934 did not have the expected
results because there was no means for its enforcement. The scientific inter-
est of the world bloomed again in 1935 because of the centenary of Darwin's
visit to Galapagos.

In 1937 the Ecuadorian Government organized its first National Scien-
tific Commission. The members of this commission, which included this au-
thor, and helped by the President in charge at that time. General Albert Enqi-
quez, took a trip to Galapagos in a warship of the National Navy, Cotopaxi
Cannoneer. On its return, a complete report was prepared which pointed to the
necessity of preserving all nature in the Archipelago and especially its rich
fisheries resources. But practically no real protection resulted. Then this au-
thor suggested the need for establishing a biological station so that scientif-
ic investigations on the Galapagos biota could be carried out and at the same
time some protection afforded the native biota. Only after 23 years, because
of interest demonstrated by the Government of Ecuador, UNESCO, and the In-
ternational Union for the Conservation of Nature, has the establishment of a
biological station on Galapagos become a reality. This research center has
been named in honor of Charles Darwin, the great British naturalist, and au-
thor of the "Origin of Species."

* Presented at the TENTH PACIFIC SCIENCE CONGRESS of the Pacific Science

Association, held at the University of Hawaii, Honolulu, Hawaii, U.S.A., 21 August
to 6 September 1961, and sponsored by the NATIONAL ACADEMY OF SCIENCES, BERNICE

Pauahi Bishop Museum, and the University of Hawaii.

-141-

142 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Galapagos is one of the most interesting scientific reserves in Ecua-
dor, and, indeed, in the world.

To preserve Galapagos as a National reserve means the protection and
conservation of its resources. Its protection is indispensable not only for my
country, but also for the world. For many years scientists and scientific in-
stitutions have been unsuccessful in coordinating their plans, but since 1957,
as a result of the studies and reports of two biologists, Dr. Robert I. Bowman
of the United States of America, and Dr. I. Eibl-Eibesfeldt of Austria, plans
moved quickly ahead for the establishment of a biological station at Academy
Bay on the south side of Indefatigable (Santa Cruz) Island. Sponsors of the
1957 reconnaissance were the International Union for the Conservation of Na-
ture, UNESCO, the International Committee for Bird Protection, the New York
Zoological Society, the Conservation Foundation, and Life Magazine. In 1959,
and coincident with the "Darwin Centennial," the Charles Darwin Foundation
for the Galapagos Isles was founded by Professor Victor VanStraelen, in Bel-
gium. The principal purpose of this international scientific organization is to
conserve the indigenous biota of Galapagos and to promote scientific research
of a fundamental nature in the Galapagos region.

Now we must ask, does the Galapagos Archipelago need only protection
or does it also need better methods of conservation?

Distinction Between "Protection" and "Conservation"

We need to distinguish between "protection" and "conservation," since
these terms are often confused.

"Protection" is a word generally used by naturalists who are not prim-
arily concerned with economic benefit or any other utilitarian exploitation.
Their point of view is mainly scientific and esthetic. They are concerned with
spiritual enjoyment for themselves and future generations. "Conservation" is
a practical and positive word with economic connotations, that is used by
those who look upon nature as a resource for exploitation, but who use mod-
ern principles of management to preserve the resources of today so that some
will remain for the future. Thus the purposes and objectives of the protec-
tionists and conservationists are rather different, technically speaking. It is
not possible to separate their activities because the protectionists also tend
to preserve the fauna, flora, and minerals; the conservationists, in turn, sup-
port the protection of certain species of plants and animals and kinds of min-
erals.

The conservationists tend to preserve definite species of animals, for
example, because they constitute an economic resource, that is to say, a na-
tural resources which must not be exhausted and thereby harm those people who
make their living by its exploitation. These people are not interested in a
species as such, but in its quantity. On the other hand, the protectionists are
preoccupied, fundamentally, with species which are disappearing or which are

No. 44) ACOSTA-SOLIS: GALAPAGOS SYMPOSIUM 143

close to extinction. The protectionist is not interested in the species for its
economic utility or for personal profit, but for science. He looks at species
as objects for scientific study.

The main difference between protectionists and conservationists is in
the application of their own concepts to the native biota and to the introduced
or exotic one. The protectionists are almost entirely preoccupied with the
protection of the native biota that forms the natural life of a specific environ-
ment, because invasions by exotic species always produce a disturbance of
the biological equilibrium of the environment where the invasion has taken
place. But the latter does not disturb the conservationists, especially if they
are hunters or fishermen. The protectionist, using scientific means, tries to
prevent the invasion of species which will disturb the natural biological en-
vironment. He does not oppose the introduction and acclimatization of exotic
species, provided they are retained in some special gardens. The introduction
of exotic species in large areas or national parks can form the basis of a new
economic resource deserving of the conservationist's attention.

For the protectionist, any species deserves protection when it is threat-
ened with extinction. The conservationist is interested only in the species of
economic value as exploitable resources of nature.

Thus insofar as Galapagos is concerned, it must be borne in mind that
both concepts, protection and conservation, are applicable to the biology and
pedology of the different islands of the archipelago.

Some Protectionist Suggestions

The protectionist suggestions given by this author since 1937 and sub-
sequently encouraged by UNESCO and lUCN reports are, in short, as follows:

1. To determine those islands or areas to be set aside as reserves for
Galapagos wildlife where effective protection can be enforced. In the areas
declared as "reserves," all hunting, agriculture, and human settlement will
be prohibited by law. Visits by tourists to these reserves will have to be
strictly controlled; only the scientific excursions under competent leadership
will be permitted; scientific collections should always be allowed but only
under strict regulation in reserve areas.

2. The areas or islands declared as "reserves" will be those which
have rare species, or species in danger of extinction, or those that have scen-
eries which are worthy of protection as a living museum of nature. Reserves
must be without settlements. In the areas where there are villages, the "re-
serves" should not be established and that is why we cannot speak about
"reserves" in Chatham (San Cristobal) and Charles (Floreana) islands; also
in the southern part of Albemarle (Isabela) Island. On the contrary, on Inde-
fatigable Island (Isla Santa Cruz) there is a special situation. The western
side still possesses a relatively undisturbed habitat with good-sized colonies

144 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

of giant tortoises, in need of protection. And in the eastern end of the same
island there are agricultural lands which have not yet been farmed and where
human population is scarce. In this case the best thing to do is to delimit the
areas: those for protection, and those for settling and agriculture. In this way
there would be less interference between the two functions, the natural biol-
ogy of the giant tortoises, and the use of the natural edaphic resources, all
managed under conservationist principles.

3. Besides the legal and technical provisions suggested since 1937 in
behalf of protection of the Galapagos biota, it will be necessary to instigate
a campaign of protectionist publicity all over Ecuador, in the grade schools,
high schools, etc., and enlist their cooperation in the governmental project,
so that they will visit the Archipelago and be spokesmen for its protection,
and by their actions set a good example. On the other hand, the campaign of
conservationist education will have to be taught to the settlers who live in
Galapagos, through lectures, illustrated pamphlets, and motion pictures. In
this way, the settlers will learn how to be responsible to surrounding nature
and to recognize the value of the native biota.

Some Conservationist Suggestions

The conservationist must bear in mind the following points when deal-
ing with the economic resources of Galapagos.

1. Recognition of the good agricultural lands in Galapagos. According
to our experience, the islands that have agricultural lands with areas or high
strips at 500 meters above sea-level are the large ones, that is to say, where
humidity and rains have permitted the formation of a thicker soil stratum, where
there is a lush herbaceous, shrubby, and arboreal vegetation. We have some
examples of these on Chatham (San Cristobal) and Charles (Floreana) islands,
on the eastern side of Indefatigable (Santa Cruz) Island, and on the south of
Albemarle (Isabela) Island.

2. After the pedological and agricultural studies, we must classify the
lands according to agricultural capacities, that is to say, to delimit them on
a special map. It is true that this work would take a long time, but on the
other hand this would show us the best use of the lands for grazing, planta-
tions, forests, horticulture, etc. Good land use is essential for maintenance
of continuous productivity of agricultural crops as well as for wildlife.

3. Careful planning of colonization and agriculture is absolutely neces-
sary for wise land use on Galapagos. The productivity of Galapagos is strictly
limited and therefore Galapagos colonization must be meticulously controlled.

Galapagos Fauna that Must be Protected Immediately

According to our personal observations in 1937, supplemented by the
findings of later investigators, the following groups of animals must be pro-

No. 44) ACOSTA-SOLIS: GALAPAGOS SYMPOSIUM 145

tected by legal decrees and also by actual enforcement.

1. The gigantic tortoises on Hood (Espanola), Duncan (Pinzon), and
Abingdon (Pinta) islands, and, if not too late, the ones in the interior of Cha-
tham (San Cristobal) Island. There are numerous torotises on Indefatigable
(Santa Cruz) and Albemarle (Isabela) islands, which are also in great danger
of extinction because of the relentless and uncontrolled hunting.

2. The land iguana needs protection, especially the small colony that
exists on Indefatigable Island. If the western portion of the island is set aside
as a biological reservation, and if we enforce the protective laws, then the
little colony can be saved and even increased in its own habitat.

3. The fur seals of Galapagos must be protected from hunters.

4. Birds of all species deserve protection and care from the commercial
hunters. Penguins and flightless cormorants are not abundant and need full
protection. The flamingos are not very common according to several reports,
and every effort should be made to fully protect this beautiful species in Ga-
lapagos.

Special Areas

In Galapagos we can distinguish several islands or special habitats for
certain groups and species of fauna and flora. In a protectionist sense the
following islands or areas may be mentioned as being of great biological im-
portance:

A. Special areas for bird protection:

1. Hood (Espanola) Island is the nesting site of the Galapagos al-
batross and where blue-footed boobies, frigate-birds, red-billed tropic-birds,
and Ion-billed mockingbirds are concentrated. The gigantic tortoise is very
rare or possibly extinct on this island. One of the longest coral-sand beaches
in all of Galapagos is situated on the north shore of the island, adjacent to
Gardner- near-Hood Island.

2. Tower (Espaiiola) Island has a large number of nesting red-footed
and masked boobies, frigate-birds, and one of the largest examples of Darwin's
finches, Geospiza magnirostris. Besides, in this island there is much beauti-
ful scenery, such as the central crater lake with its mangrove swamps and the
picturesque Darwin Bay.

3. Narbo rough (Fernandina) Island constitutes the largest home of
the Galapagos penguin and flightless cormorant. Here there are large colonies
of land and sea iguanas, and the native rat (Nesoryzomys narboroughi). The
scenery of the central crater of this island is magnificent. There are hot sul-
phur springs and very fresh lava flows, all of which are of much interest to
geologists and volcanologists. In the fresh water that formerly occurred in
the central crater, a fish has been collected, hitherto unknown for the Galapa-
gos region. The gigantic tortoises still occur on the south side of the island.

146 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Narborough Island is very important to scientists because of its primitive na-
ture and the fact that the biota has not been spoiled with the exotic plants and
animals that have found their way to all the islands with permanent human hab-
itations such as Chatham (San Cristobal), Charles (Floreana), south Albemarle
(Isabela), and Indefatigable (Santa Cruz) islands.

4. Culpepper rocks, forming the most northerly point in the Gala-
pagos Archipelago, is the appropriate site for the large concentration of sea-
birds, including boobies, frigate-birds, terns, and petrels.

B. Special areas for the protection of the gigantic tortoises:

1. Indefatigable (Santa Cruz) Island is by far the most interesting
of the reserves for the gigantic tortoises. These large reptiles have been dis-
appearing because of abuse from colonists, hunters, and collectors. The west-
ern half of Indefatigable Island must be set aside as a reserve in which no
agriculture will be permitted.

2. Duncan (Pinzon) Island has some giant tortoises still remain-
ing on its south side. If we keep out the hunters and collectors we should be
able to restore this small colony to its former level of abundance.

3. Abingdon (Pinta) Island still likely has a few tortoises. Full
protection should be afforded those few remaining animals.

4. Albemarle (Isabela) Island has many tortoises and is second
only to Indefatigable Island as an important reservoir of these animals. From
Perry Isthmus to the north end of the island should be kept as a reserve. Much
could be done to teach the colonists on the southern part of Isabela Island
about the necessity of protecting these chelonians.

C. Special areas for the protection of land iguanas:

1. Harrington (Santa Fe) Island is the home of thousands of land
iguanas and feral goats. Land iguanas have survived the inroads on their num-
bers made by commercial hunters. From now on hunting must be curtailed and
the civil authorities must assist in the patrol work.

2. Plaza Island, located at the east end of Indefatigable (Santa
Cruz) Island, constitutes the typical habitat of a pink-colored iguana. Be-
cause of their small numbers there is great danger of extermination by hunt-
ers. This island also harbors sea lions, petrels, tropic-birds, and because of
certain unusual geological aspects, it constitutes a very important area in need
of reserve status.

3. Narborough (Fernandina) Island, in addition to being a reserve
for birds, must be considered as a reserve for the marine and land iguanas; at
present, the colony of land iguanas is very large and great herds of marine
iguanas may be found along the outer shores. But I repeat, they need official
and scientific control.

FUTURE SCIENTIFIC STUDIES
IN THE GALAPAGOS ISLANDS*

Jean Dorst

Museum National D'Histoire Naturelle,
Paris, France

The Galapagos Islands rank among the most celebrated places in the
world, since they provide one of the most clearcut natural experiments in or-
ganic evolution. Every biologist, once in his life, should go on a pilgrimage
to the spot where one of the greatest achievements of science was born.

It was in the Galapagos that young Charles Darwin found his inspira-
tion. In July, 1837, not later than two years after his visit to Galapagos, Dar-
win wrote: "I opened my first notebook on Transmutation of Species. Had
been greatly struck from about month of previous March on character of South
American fossils and species on Galapagos archipelago. These facts origin
(especially latter) of all my views."

These prospects are not only of historical and retrospective value. The
islands are still today "evolution's workshop and showcase," and they have
maintained the same importance up to the present time, where a great deal of
research remains to be done in various fields.

Of course, evolution is observable anywhere in the world, but the trends
and the laws which govern the phenomenon often are hidden by complexity and
by the innumerable factors involved. On the contrary the simplification of the
Galapagos ecosystem makes it much more apparent in these islands.

Numerous studies in systematics have already been done on the Gala-
pagos. Vertebrates have been the most thoroughly studied, except the smaller
reptiles and the endemic rats. Nevertheless most of the investigations on in-
vertebrates are outdated or even completely missing. The inventory of all liv-
ing creatures, from the smallest to the giant tortoises, must be undertaken by
priority with all the modern concepts in mind. This will form a basis for fu-
ture studies on the Galapagos fauna and especially those dealing with the
biological aspects. Studies in systematics will also shed new light on the
problems of speciation and on evolution in progress. Owing to the laws which
govern evolution among invertebrates, we may assume that a better knowledge

Pauahi Bishop Museum, and the University of Hawaii.

- 147

148 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

of the microfauna could lead to a better understanding of many biological prob-
lems. In recent years, scientists have brought new techniques to a high degree
of perfection, especially in the field of genetics, chromosome analysis, bio-
chemical tests like chromatography, and even micromorphology. Many Galapa-
gos animals could be tested by such techniques and the results may give clues
to their interrelationships and on the modes of evolution in each group.

This applies especially to genetical investigations. The geneticists
have now achieved a great deal of information on the mechanism of heredity.
New methods and large scale experiments have been undertaken. But we may
wonder why no one has tried to apply these techniques to the Galapagos ani-
mals or plants — a wonderful field for experimentation owing to the simplifica-
tion of the problems involved as mentioned above.

However, evolutionary studies are only one aspect of the investigations
to be undertaken in the Galapagos, where biological researches of all types
might be successful.

One of the many fields of investigation could deal with behavior, some
very peculiar trends being observable on these islands. The earlier natural-
ists reported on strange behavior patterns to be observed among Galapagos
birds and reptiles. Development of these patterns are, in large part, under the
influence of the very particular conditions prevailing in the islands, where
the number of species is smaller than anywhere else, and where few enemies
are present, the mammals being almost completely absent. The splitting of spe-
cies into local populations, owing to isolation on islands with no communica-
tion, has a role which can not be minimized. A great deal of observation con-
firms that the trends apparent in behavior have paralleled those observed in
morphological diversification.

One of the best examples is to be found among the well known Darwin's
finches or Geospizinae, studied from the morphological point of view by David
Lack (Darwin's Finches, London, 1947) and recently by Robert Bowman (Univ.
Calif. Publ. Zool. 58, 1961). The evolution of these fringillids shows a per-
fect adaptive radiation in morphology and anatomy in relation to diversity of
habitats and ecological niches. They also show a very elaborate evolution in
behavior patterns, and especially in vocalizations. In the last few months Dr.
Bowman has undertaken a thorough study of these aspects with modern tech-
niques. But some other aspects might be investigated with success and such
researches have to be extended to other birds like the Galapagos mockingbirds
(Nesomimus) differentiated into several geographical races. Such studies,
which in recent times brought so many interesting facts to our knowledge,
must be extended to all Galapagos birds and also to the reptiles, especially
the marine iguana ( Amblyrhynchus cristatus), one of the most interesting rep-
tiles in the world. This lizard, with numerous adaptations to conditions in the
sea, from which it never straggles far, shows very strong tendencies to gre-
gariousness, especially along the shores of Narborough Island, where colonies

No. 44) DORST: GALAPAGOS SYMPOSIUM 149

of many hundreds may be observed; but anywhere else this iguana is more or
less gregarious and single individuals are met very seldom. This social be-
havior may be very interesting to investigate carefully in relation to ecologi-
cal factors. Of course, these chosen examples are only a few among the many
which could be studied in the Galapagos.

Furthermore one of the main tasks for scientists in these islands is to
study the Galapagos ecosystem. This aspect of investigation has a particular
importance in the light of conservation of nature and wildlife. Nature is badly
threatened in the Galapagos as a consequence of human impact. When they
were discovered in 1535 by the Bishop of Panama, Tomas de Berlanga, they
were in a virgin condition. Since this not so remote time, various people set-
tled, destroyed the habitats, and killed the animals, sometimes for food, some-
times for "fun." Moreover, domestic animals, and especially goats and pigs,
have been introduced and soon became feral. They fundamentally modified the
balance of nature and contributed in a very large measure to depletion of stocks
of endemic species and disruption of natural habitats. Therefore many species
are on the verge of extinction and some must already be considered to have
vanished completely. To preserve what is left we must undertake a thorough
ecological study of the environment in the Galapagos.

The pedological analysis is one of the first tasks as it will constitute
the basis for all further work. It will also be a wonderful field of investigation
in itself, since the Galapagos, purely volcanic in origin, offer various stages
of transformation and colonization of lava flows by microorganisms and plants.
All stages from pure mineral soil to top-soil, where cultivation is possible (in
some very limited areas), are present in these islands. A detailed study of
the soils, in relation to the geologic history of the islands and chronology of
the various lava flows and volcanic eruptions, might lead to discovery of some
very important facts and to a better understanding of the evolution of land of
volcanic origin. By the way, it could also give a basis for better land use,
avoiding utilization for agricultural purposes of land that is better kept in its
natural state.

The second stage of such a broad ecological survey is a thorough study
of structure of vegetation. Provided a complete systematic list of all plant
species living in the Galapagos is available, it would be a fascinating work
to describe the various plant communities and to follow their evolution. These
communities range in type from real desert biomes with a highly characteristic
spaced distribution of cacti and spiny bushes, with large barren areas in be-
tween, to grasslands, and dense moist forests, among which the lofty Scale-
sia trees, an endemic genus of Compositae, are the most conspicuous plants.
Many forms of plants could be studied in relation to the different life zones.
Besides knowledge of their relationship — especially in Scalesia, wild toma-
toes and cacti — could lead to very interesting conclusions on plant evolution.
These studies, in relation to climate and soil distribution, must be synthesized

150 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

and then summarized in a detailed vegetation map covering the whole Archi-
pelago, a great need for all scientists working in this part of the world.

Like animals, plants have been modified to a large extent by the impact
of species introduced by man, voluntarily or not, and which compete with en-
demics and often compel them to modify their response. We have at our dis-
posal numerous data collected by earlier botanists. Comparison with the con-
temporary situation could be of the greatest interest for a historical approach
to an understandingof any fluctuations in the make-up of the flora, and of course
to preserve some of the most typical, and still untouched, habitats.

With this pedological and botanical background zoologists could then
undertake their various investigations on terrestrial communities. Soil com-
munities are of primary interest and, as their elements probably show marked
differences from what is known in other places, the complete study of the sys-
tem could be of the greatest interest. Soil ecology yet remains so little under-
stood over the world that this particular aspect of investigations in the Gala-
pagos Islands could give some clues to several problems as yet unsolved. If
we take into consideration the upper levels of the ecosystem, we may imagine
that here also we could bring new facts to light. There are few mammals and
most of the terrestrial vertebrates are birds or reptiles. Leaving aside the
birds, the place of tortoises, land iguanas, and smaller lizards in the ecosys-
ten is to be investigated thoroughly, and, besides being of interest in itself,
this may give a good idea of what life was like in former times. In the Gala-
pagos we are faced with a "fossil biocenosis." Many adaptations, some very
strict, may be found between reptiles and plants. Recently Rick and Bowman
(Evolution, 15, pp. 407-417, 1961) emphasized the fact that the seeds of na-
tive tomatoes, subject to a dormancy of indefinite duration, may be activated
in the digestive tract of the giant tortoises. The passage through the gut, re-
quiring from one to three weeks and even longer, produces a marked improve-
ment in speed and percentage of germination. Thus tortoises may be the main
agents for breaking the dormancy and also for actually spreading the seeds
through their droppings — a very important adaptive device. Similar examples
of symbiosis might be found in many other aspects of the Galapagos biota,
which, from the biological point of view, constitutes a distinct world in itself,
evolved in isolation from the rest of the world.

To get information on the evolution of the balance of nature in the Ga-
lapagos, much routine work is to be undertaken immediately under the direct
guidance of the Darwin Research Station, beginning with censuses of all threat-
ened species in well defined areas or along carefully chosen linear transects.
Periodically, i.e., several times a year, reptiles and birds must be numbered.
These figures will provide data on their seasonal fluctuations, the dynamics
of their populations, very important basic facts that must be known if we want
to succeed in protecting them efficiently.

No. 44) DORST: GALAPAGOS SYMPOSIUM 151

Evolution of plant communities and of habitats will be watched within
quadrates established in different areas, surrounded by fences and even rat-
proof walls; periodical surveys will be undertaken to see how the vegetation
cover is modified under natural conditions. Comparison with unprotected areas
will measure the importance of the impact of feral animals on the plants. This
work is of primary importance as a background for all types of researches in
the Galapagos, and also as a basis for the recommending of practical mea-
sures to safeguard the wildlife.

If research on terrestrial biomes is of such great importance for the fu-
ture of this invaluable natural heritage, we must not however forget that the
seas surrounding the archipelago also constitute a unique field for investiga-
tions by oceanographers. This part of the Pacific is probably one of the most
complex of all marine sectors. Several currents of various origins meet here,
carrying waters of very different characteristics. The Humboldt Current, flow-
ing from the East, brings cool Antarctic waters, producing oceanographic con-
ditions seemingly paradoxical for islands situated on the equator; it mingles
with warm eastward flowing waters brought by the Equatorial counter-current
and subsurface Cromwell Current, and by a current coming from the Gulf of Pan-
ama. From this odd situation results a juxtaposition of warm and cold areas,
often very distinct and visible like a mosaic of different colors, and an inter-
mingling of marine faunas of various origins. Fur seals and penguins are liv-
ing side by side with flying fishes and tropic-birds; the same may be observed
among marine invertebrates.

Distribution of marine plants and animals within the whole archipelago
must be carefully investigated in relation to oceanographic conditions. This
aspect of the researches will probably bring to light some very interesting
facts such as a narrow range of adaptations of various organisms to certain
physical factors of sea waters.

These investigations could also be of the greatest significance to the
economic development of Galapagos. Seas surrounding the archipelago are nu-
tritionally very rich, and many fishes, the size of which ranges from the small
herring to the big albacore, swarm in these waters. A local fishing industry
has already been established on a very small scale, but with encouraging re-
sults. We must bear in mind that cropping of marine products is the only na-
tural resource of direct economic importance in the Galapagos where agricul-
ture will never be successful, except within very limited areas, owing to water
shortages and untillable land. Efforts to promote agriculture as a resource to
attract settlers or to encourage a major expansion of cultivation, would mean
poor land use with concomitant destruction of habitats suitable to wildlife,
that could never be restored. But if we want to save these islands, so famous
to scientists, we must give to settlers a higher standard of living — the best
way to discourage cropping of tortoises and destruction of habitats, as is true
everywhere in the world. We are convinced that economic development of the

152

CALIFORNIA ACADEMY OF SCIENCES

(Occ. Papers

Galapagos Islands must consist of a rational exploitation of the sea, a contri-
bution of great value to the many Ecuadorians who suffer from an acute pro-
tein shortage. Such exploitation must be based on scientific facts if we are to
manage properly the fishery so as to avoid over utilization and consequent
depletion of the resource. Our research station may assume this tesponsibility
in cooperation with several other organizations interested in oceanographic
researches in this part of the Pacific Ocean, such as the Inter-American Tro-
pical Tuna Commission and FAO Laboratories. Thus we should integrate into
the plan of economic development of Ecuador, which is a point of very great
importance both on technical and psychological grounds.

The program of investigation is therefore unlimited. For all these rea-
sons it was urgent to establish a research station in these islands. This has
now been done thanks to the action of the Charles Darwin Foundation for the
Galapagos Isles, which organization was founded in 1959 and is governed by
an Executive Council including representatives from all nations interested in
these researches. With funds raised in several countries, the construction of
a field station has been achieved at Academy Bay on Indefatigable Island
(figs. 1 and 2). The station is already in operation and material improvements
continue to be made. The main purpose of the Darwin Foundation is to offer
scientists of all disciplines and nationalities living accomodations and work-

Figure 1. General maintenance building of the Charles Darwin Research Station, Academy
Bay, Indefatigable Island, Galapagos. Photo, courtesy R. Leveque, December, 1961.

No. 44)

DORST: GALAPAGOS SYMPOSIUM

153

«^

t9>fM^^'

Figure 2. Main laboratory building of the Charles Darwin Research Station, Academy
Bay, Indefatigable Island, Galapagos. Photo, courtesy R. Leveque, December, 1961.

ing facilities in a well equipped field laboratory. Basic equipment for scien-
tific research, especially in the field of biology, will be available to all visit-
ing scientists approved by the Foundation. A small research vessel for trans-
portation and oceanographic studies will soon be available for use within the
limits of the archipelago.

The Darwin Research Station is run by its own scientific and technical
staff which cooperates fully with investigators working under Foundation au-
spices. Routine scientific work is done by the staff, including meteorological
and oceanographic measurements, censuses of animals, studies on changes in
habitats, etc. Of course, particular scientific investigations will be undertaken
by visiting specialists.

But our main objective is to make the station open to visiting scientists
working on special projects from many branches of science, from geology to
oceanography to terrestrial ecology. It is the intention of the Foundation to co-
operate with all scientific organizations throughout the world that are inter-
ested in Galapagos research.

It must be remembered, of course, that we are the guests of the people
of Ecuador, its government and institutions, which have given enthusiastic
support to our efforts, and with which we are cooperating in all our activities.

154 CALIFORNIA ACADEMY OF SCIENCES (Occ. Papers

Collaboration with the scientific authorities is especially important and it
will be a great accomplishment indeed when young Ecuadorian scientists study
together with foreign specialists in our Station, a real international crossroad.

Moreover, we hope that the Ecuadorian government will consult with the
Foundation in matters concerning the conservation of nature in Galapagos.
All legal measures must be taken by Ecuador, for it is not our intention to in-
terfere in any manner whatsoever with its sovereignty. We are willing, however,
to answer official requests for advice, on the basis of scientific investiga-
tions made under Foundation auspices.

Our Foundation is probably unique in its class. It is an international
institution whose aim is to advance our scientific knowledge specifically in
the Galapagos region and to conserve the remarkable biota inhabiting it. The
evolutionary theories of Charles Darwin, which belong to mankind as a whole,
completely justify such an organization. On the other hand, the invaluable
natural inheritance of Galapagos wildlife was threatened by men of all nation-
alities; it is logical, therefore, that scientists and conservationists from all
nations collaborate with the Ecuadorians to study and save what is left of
these islands for the benefit of generations to come.

MBl. WHOI LIBRARY

UH ITFV J

Internet Archive Audio

Featured

Top

Images

Featured

Top

Software

Featured

Top

Books

Featured

Top

Video

Featured

Top

Mobile Apps

Browser Extensions

Archive-It Subscription

Save Page Now

Full text of "Occasional papers of the California Academy of Sciences"

See other formats