JOURNAL

of the Linnean Society

Bicentenary Joint Meeting with
the Botanical Society of the
British Isles

VOLUME 101 NUMBER 3 NOVEMBER 1989

Published for

the LINNEAN SOCIETY OF LONDON
by ACADEMIC PRESS

H ISSN 0024-4074

BOTANICAL JOURNAL OF THE LINNEAN

SOCIETY

EDITORIAL BOARD OF THE BOTANICAL JOURNAL

EDITOR:

Dr S. L. Jury

Department of Botany, University of Reading,
P.O. Box 221, Reading RG6 2AS

ASSOCIATE EDITORS:

Dr R. Allkin (numerical methods)
Computing Section, Royal Botanic
Gardens, Kew, Richmond TW9 3AB

Dr P. E. Brandham (cytology)

Jodrell Laboratory, Royal Botanic Gardens,
Kew, Richmond TW9 3DS

Dr P, R. Crane (North American authors)
Department of Geology, Field Museum
of Natural History, Lake Shore Drive,
Chicago IL 60605

Dr Q. C. B. Cronk

(conservation and plant geography)

Botany School, Downing Street, Cambridge
CB2 3EA

Dr M. W. Dick (fungi and algae)
Department of Botany, University of
Reading, P.O. Box 221, reading RG6 2AS

Dr Dianne Edwards (palaeobotany)
Department of Geology, University of Wales
College of Cardiff, P.O. Box 914, Cardiff
CF1 3YE

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President: Prof. M. F. Claridge

Botanical Secretary: Dr F. A. Bisby
Editorial Secretary: Prof. J. D. Pye

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Botanical Journal of the Linnean Society (1989), 101: 261.

jM

Botanical Society of the British Isles Conference Report Number 21

Preface

Heathers and heathlands

Edited by S. L. JURY

The eight contributions contained in this issue were presented at a symposium
entitled ‘Heathers and heathlands’/ held in the rooms of the Linnean Society of
London on Thursday 20 October 1988. The meeting was organized jointly by
the Botanical Society of the British Isles (B.S.B.I.) and the Linnean Society as
part of the celebrations of the bicentenary of the foundation of the Linnean
Society. It was attended by 143 participants, who filled the meeting room, with a
significant number of late registrations sadly turned away.

The B.S.B.I. celebrated its own sesquicentenary in 1989 and, like the Linnean
Society, has a long and valued tradition of contributions to British and Irish
botany. The two Societies have collaborated before, but their coming together
on this occasion resulted in a particularly happy and successful day, both socially
and scientifically. Other joint meetings are thus likely to be held in the future.

Heathers and heathlands constitute a characteristic community of Atlantic
Europe, and constitute a large and important part of the vegetation of the British
Isles, perhaps not given the attention deserved by scientists. It was, therefore, a
welcome suggestion by Mr David McClintock that they should form the theme
of this meeting.

However, it was pleasing to be able to include in the programme a paper by
Mr E. G. H. Oliver of Stellenbosch on the Ericoideae and the southern African
heathers. This contribution put the impoverished British and European
ericaceous flora into context. It is unfortunate that the paper printed here
cannot include the spectacular colour photographs that he showed to the
conference or convey the impression made by a spectacular display of living
plants that he had brought and assembled.

Both Societies wish to pay tribute to Dr F. A. Bisby and Mrs M. Briggs who
undertook much of the hard work in putting the programme together, ably
assisted by Dr N. K. B. Robson. We are grateful to Cdr J. Fiddian-Green, at the
time Executive Secretary of the Linnean Society, who oversaw the
administration and domestic arrangements, and to his staff. Thanks are also due
to the chairmen, Professor C. A. Stace and Professor C. H. Gimingham.

Reading, May 1989 S. L. Jury

261

Botanical Journal of the Linnean Society (1989), 101: 263-268.

Heather and heathlands

C. H. GIMINGHAM

Department of Plant Science, University of Aberdeen, St. Machar Drive,
Aberdeen AB92UD

GIMINGHAM, C. H., 1989. Heather and heathlands. Studies of the biology and ecology of
heather ( Calluna vulgaris (L.) Hull) reveal a remarkable combination of characteristics, accounting
for its success as a heathland dominant and its ability to persist under traditional forms of use and
management. New work on the life history and physiology of the species is helping to explain recent
changes in heathlands, and to develop appropriate methods of conservation.

ADDI TIONAL KEY WORDS: — Calluna - Ericaceae - ecology - life history.

CONTENTS

Introduction . 263

Attributes of Calluna . 264

Calluna as a dominant of mountain heaths, and on peat . 265

Calluna as a dominant of heathlands . 265

Conclusion . 268

References . 268

INTRODUCTION

Heather ( Calluna vulgaris (L.) Hull) must by now be one of the most intensively
studied of British plants. While this gives a remarkable and fascinating insight
into the biology and ecology of the species, it is certainly not the case that we
know all there is to know about it, or even all we need to know for purposes of
using, managing or conserving it. It is quite a long time since the first
comprehensive monographs and accounts of Calluna vulgaris were being
published (Nordhagen, 1937; Beijerinck, 1940; Gimingham, 1960), but there is
still a great deal of extremely interesting research involving this plant in progress
at the present time, yielding exciting new information and requiring the revision
of preconceived ideas.

Calluna has many claims upon our attention. For example, there can be few
sights more rewarding than heather in full flower, whether viewed at close
quarters in a garden or from a distance in mass on a hillside. But in addition to
its contribution to horticulture and landscape, it also supports wild herbivores ol
use to man and since Neolithic times has provided valuable grazing on poor soils
for his domestic animals. As a dominant of extensive tracts of country, it has
given rise to distinctive landscapes and has supported rural communities within
which unique customs, implements and breeds of sheep and cattle have evolved.
These are the landscapes we know as heathlands. This paper addresses the role of

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C. H. GIMINGHAM

heather as the leading dominant of west European heathlands, and seeks to
identify some of the biological and ecological characteristics of the species on
which that role depends.

ATTRIBUTES OF CALLUNA

Heather is essentially a European species. Its geographical distribution
extends from N. Scandinavia and Iceland to the Mediterranean and from the
Atlantic seabord to the Urals. However, it is only in the more oceanic and
montane parts of this range, and only where trees or tall shrubs are lacking, that
Calluna can become widely dominant of heathlands.

To be sufficiently vigorous to exclude competitors and attain dominance,
Calluna requires the absence of shade, a moist atmosphere and soil throughout
much of the year, and relative freedom from temperature extremes. These
conditions can be obtained in oceanic west Europe and at appropriate altitudes
in the mountains, and here Calluna is the dominant species in a number of
distinct plant associations and over quite a wide range of habitats.

Certain general properties of Calluna contribute to its ‘success' across this range
of environmental conditions. One is its capacity to perform effectively on acidic
soils which are low in plant nutrients, especially phosphorus and
nitrogen — conditions which tend to depress the growth of many of its
competitors. It has been suspected that this ability to maintain vigorous growth
in oligotrophic habitats relates, in part, to the ericoid type of mycorrhiza in the
roots of Calluna. The role of this mycorrhizal association has still to be fully
explored, but there can be little doubt of its importance. Bajwa & Read (1986),
for example, have shown that many amino-nitrogen sources can be utilized by
the mycorrhizal fungus of Calluna. The subsequent demonstration by Abuarghub
& Read (1988) that amino-acids may occur in some quantity in the organic
horizons of heathland soils suggests that the ericoid mycorrhiza may be very
important for the nitrogen economy of Calluna on these soils.

A further relevant attribute of Calluna is the freedom with which it produces
adventitious roots from stems which are in contact with or become buried in
moist litter, humus, peat or even dense vegetation such as Sphagnum or other
mosses. This capacity is by no means confined to young branches, the first
formed of which often trail along the ground and begin to root, but can be seen
(or produced experimentally) on quite old, woody stems (Scandrett, 1987). In
freely-drained soils, Calluna is able to root deeply by the development of its
primary root systems, but in moist humus or peat a dense mass of feeding roots is
produced adventitiously near the soil surface.

Thirdly, Calluna displays remarkable plasticity in its above-ground growth-
form. This results largely from the way its branch system is made up primarily of
a combination of long-shoots (the main axes of growth) and short-shoots (laterals
of limited growth; the chief photosynthetic units). Normally, at the start of a new
season’s growth each long-shoot apex is replaced by two to four new long-shoots,
keeping shoot density at the periphery constant as the bush expands radially.
Typically, this produces a dome-shaped shrub, but if at any time a long-shoot
apex is destroyed or damaged, any of the short-shoots can grow out into new
long-shoots. Although the shape of the bush is then distorted, the plant can
continue to grow in various directions depending on the position and frequency
of damage.

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265

CALLUNA AS A DOMINANT OE MOUNTAIN HEATHS, AND ON PEAT

These three main attributes help to account for the ability of heather to
establish dominance in highly wind-exposed habitats on the one hand, and on
growing peat surfaces on the other. On mountains, long-shoots rising above a
few centimetres may be killed, confining growth to lateral branches or even basal
short-shoots, while destruction of all apices on one side may lead to a trailing
type of growth in which extension is always in one direction. This, coupled with
adventitious rooting from the trailing stems, enables the plant to form the
familiar low mats or ‘waves' on mountain plateaux. In addition to this plastic
response to environment, Grant & Hunter (1962) have shown that genotypes in
which the same pattern of growth is fixed have been selected in high altitude
populations.

On peat surfaces at lower altitudes, the behaviour of heather is different,
through determined by the same attributes. Here, where the substratum is wet,
extension growth of the main frame-branches is active but rather lax and
straggly, such that the main stems readily spread outwards and sag, their bases
often becoming buried in moss or growing peat. With the development of
adventitious roots, this results in a form of ‘layering' and may lead to a type of
vegetative spread in which one original individual gives rise to a ring (or part
ring) of offsets (Keatinge, 1975). This behaviour, which enables Calluna to share
dominance with Eriophorum vaginatum, for example, in a rather stable community
(Forrest, 1971) is possible only where the peat surface is aerated for at least a
part of the growing season. ( Calluna cannot withstand continuous waterlogging. )

CALLUNA AS A DOMINANT OE HEATHLANDS

At middle and low altitudes, extensive heathlands with Calluna as dominant
have occupied freely-drained, often podsolic, soils in many parts of the "heath
region’, for example in S. Sweden, Denmark, N. Germany, The Netherlands,
Belgium, N. and W. France, N. Spain and the British Isles. Throughout most of
this region evidence from pollen analysis, archaeology and historical records
shows that the heaths were derived from former forest as a result of human
impact. Calluna was doubtless a component of forests on acid soils, whether pine
forest in the north or broadleaved forests further south. Although the shade cast
by tree canopies may inhibit flowering and gradually reduce shoot production
until the bushes die (Hester, 1988), Calluna is an ‘opportunist' species and
certainly made use of the many gaps and glades in the natural and semi-natural
woods.

The ability of Calluna to colonize and dominate extensive areas once trees had
been cleared may be related to the fact that it has some of the characteristics of
pioneer or ‘r-selected' plants. These include a very high reproductive capacity
and readily dispersed seeds. Estimates of seed production range from about
250 000 (Mallik, Hobbs & Legg, 1984) to 1 million per square metre in a
vigorous stand, the seeds being very small, light and readily dispersed by wind.
Viability is high and germination takes place abundantly, given sufficient
moisture in the medium and exposure (at least for short periods) to light. A

266

C. H. GIMINGHAM

majority of the seeds can germinate soon after shedding, though some have a
dormancy period and this ensures that germination will continue intermittently
even if a first crop of seedlings fails to survive. Furthermore, if conditions are
unsuitable for germination but suitable for storage, the seeds are long-lived and a
large soil seed-bank is set up.

Heather, therefore, is an effective colonist on appropriate soils and this
contributes to its ability to initiate the formation of heathland. However, it is not
necessarily able to retain dominance in the same way as at the higher altitudes or
on certain types of peat surfaces. Although on podsols the lowermost branches
may root adventitiously in damp moss or humus, the plant normally adopts a
radiating, dome-shaped form as described above, and lateral spread is limited.
A. S. Watt (1947, 1955) showed that in the course of time, often after some
20 years, a Calluna bush begins to open up with the formation of a central 'gap'
in its canopy, while from the age of about 30 it generally begins to degenerate
and may eventually die back completely. Watt took the view that after an
intervening period of occupancy by other species, Calluna might recolonize the
spot it had vacated, so establishing a vegetation cycle. This has been questioned,
but recent work has confirmed that it does occur (Scandrett, 1987; Gimingham,
1988), though only in default of the arrival of some other species which will
continue the process of succession. In these habitats Calluna is essentially a serai
plant, giving place to other species: sometimes grasses or bracken Pteridium
aquilinum ) but often trees such as birch (. Betula spp.), pine (Pirns sylvestris) or oak
( Quercus spp.). These invaders find regeneration niches where gaps occur in the
centres of old Calluna bushes, or on the wider areas sometimes vacated by
simultaneous die-back of whole stands.

Nevertheless, it remains true that Calluna continuously dominated many
heathlands over considerable periods of time. This can be explained only in
relation to the use and management of these areas by man, and to the properties
of Calluna which have enabled it to respond favourably to these influences. Three
types of use and management will be touched on: grazing (often accompanied by
burning), cutting and sod removal.

First, grazing, especially by sheep and cattle, has been a widespread use of
heather over thousands of years. Here it is again the growth morphology of the
plant that accounts for its ability to withstand the impact of herbivores, for as
soon as a young, unlignihed long-shoot is bitten off, any of the surviving short-
shoots below the cut can resume growth as new long-shoots. Futhermore,
because every branch grows from a small lateral bud laid down near the long-
shoot apex at the end of the growing season, it retains at its base a group of
dormant meristems marking the positions of the leaf axils of that bud. If most of
the distal green shoots are eaten off, these meristems can then form new shoots to
continue growth. Thus Calluna can survive removal of between 40 and 60% of
the current year’s production of green shoots, although more severe defoliation
(especially in summer) may eventually cause death (Grant, 1971). Mild grazing
tends to keep the plant in a dense, relatively juvenile form in which rather little
new wood is formed.

However, it is not always possible to keep up this level of utilization in the
summer, and even when subject to grazing the plants may continue to partition
assimilate to wood, and to pass into the mature and degenerate phases. It
therefore becomes necessary to supplement grazing management by burning, in

HEATHER AND HEATHLANDS

267

order to remove the old, woody above-ground parts of the plant. If this is done
before the plant is too old, it is able to regenerate vegetatively by resprouting
from the base where, again, there are dormant buds in the positions from which
branches were formed (Mohamed & Gimingham, 1970 ; .

A further point about grazing and burning is that both practices result in the
removal of plant nutrients from the system, thus preventing a build-up of
nutrients which would be inclined to favour competitors rather than the heather.

Grazing has been practised in many parts of the heath region, often
supplemented by burning which, especially in north Britain, became a regular
means of management. In southern England, France and elsewhere cutting was
the main form of management. Cut heather was used for bedding animals and
for roof thatch, and bales of it made a resilient foundation for roads and tracks.
The heather plant responded exactly as with burning, and again nutrients were
removed from the system in the harvest of the bushes.

Finally, a rather different form of heathland use and management became
traditional in The Netherlands and North Germany. Known as ‘plaggeff, this
involved grazing flocks of sheep on the heathland during the daytime and
bringing them in to a barn at night where whole sods which had been cut from
an area of heath, including the upper organic horizon of the soil and the heather
vegetation it carried, were used for bedding. Eventually this material, well
trodden and with dung and urine incorporated, was used as fertilizer for fields
around the village, giving rise to productive ‘plaggen soils’. The areas from
which the sods had been removed were allowed to regenerate, and because the
newly exposed mineral soil contained a substantial proportion of the soil seed-
bank, Calluna (or in wetter areas Erica tetralix ) recolonized vigorously.
Furthermore, the combination of grazing and sod removal represented a
continuous transfer of nutrients from the heath to the neighbourhood of the
village (Gimingham & de Snridt, 1983). Sod cutting was also practised in
southern England, though usually as a source of fuel (Webb, 1986).

Although some heathlands are still grazed and burning remains a regular
practice on grouse-moors and hill sheep farms in Scotland and N. England, in
most areas traditional forms of management have declined or disappeared and
now the results of nutrient accumulation are beginning to be seen. To the
normal return of nutrients to the soil surface with the deposition of plant litter
there is now a considerable addition from polluted rainfall. In Denmark, The
Netherlands and Germany, Calluna is undoubtedly giving place to competitors
such as wavy hair-grass (. Deschampsia fiexuosa ) and it may be that the competitive
balance has been shifted in favour of the latter by an increase in available
nutrients (Heil & Diemont, 1983). It seems also to be the case that in these areas
Calluna may have become more susceptible to attack by heather beetle ( Lochmaea
suturalis ) and it has been shown that there is a correlation between severity of
beetle attack and the level of nitrogen in the shoots of Calluna. Some very recent
results obtained in Germany suggest that senescence in Calluna may be hastened
by increased availability of nitrogen, which seems to cause detectable changes in
both structure and physiology. In this kind of way an increase of nutrients in the
rooting region of the soil may simultaneously depress the vigour of heather and
improve that of competing grasses. The ecological significance of these ideas has
still to be tested, but they appear to indicate a possible mechanism underlying
observed changes in the composition of heathlands.

268

C. H. GIMINGHAM

CONCLUSION

The examples discussed above bear out the claim that Calluna vulgaris is a
remarkable species. It possesses the attributes of an opportunist serai species, but
because of certain morphological and life-history traits it responds well to
grazing and a variety of other types of management. As a consequence it has,
over very long periods of time, remained the dominant of semi-natural heath
vegetation under human influence. Currently there are signs that discontinuance
of management, coupled in places with high nutrient input from polluted
rainfall, may result in the replacement of Calluna by other species, such as grasses
or bracken. This raises important issues in respect of heathland conservation. To
retain Calluna dominance in future it will be necessary to manage in such a way
as not only to keep the plants in a vigorous condition but also periodically to
deplete the stock of nutrients in the system.

REFERENCES

ABUARGHUB, S. M. & READ, D. J., 1988. The biology of mycorrhiza in the Ericaceae. XI The distribution
of nitrogen in soil of a typical upland Callunetum with special reference to the ‘free’ amino acids. New
Phytologist, 108: 425-431.

BAJWA, R. & READ, D. J., 1986. Utilization of mineral and amino-nitrogen sources by the ericoid
mycorrhizal endophyte Hymenoscyphus ericae and by mycorrhizal and non-mycorrhizal seedlings of Vaccinium.
Transactions of the British Mycological Society, 87: 269-277.

BEIJERINCK, W. 1940. Calluna, a monograph on the Scotch heather. Verhandelingen der koninklijke nederlandsche
akademie van wetenschappen. Amsterdam (3rd section), 38: 1-180.

FORREST, G. I., 1971. Structure and production of North Pennine blanket bog vegetation. Journal of Ecology,
59: 453-4 79.

GIMINGHAM, C. H., 1960. Biological Flora of the British Isles, Calluna vulgaris (L.) Hull. Journal of Ecology,
48: 455-483.

GIMINGHAM, C. H., 1988. A reappraisal of cyclical processes in Calluna heath. Vegetatio, 77: 61-64.

GIMINGHAM, C. H. & DE SMIDT, J. 1983. Heaths as natural and semi-natural vegetation. In M. J. A.
Werger & I. Ikusima (Eds), Man’s Impact on Vegetation: 185-199. The Hague: Junk.

GRANT, S. A., 1971. Interactions of grazing and burning on heather moors. 2. Effects on primary production
and level of utilisation. Journal of the British Grassland Society, 26: 173-181.

GRANT, S. A. & HUNTER, R. F., 1962. Ecotypic differentiation of Calluna vulgaris (L.) Hull in relation to
altitude. New Phytologist, 61: 44-55.

HEIL, G. W. & DIEMONT, W. H., 1983. Raised nutrient levels change heathland into grassland. Vegetatio,
53: 113-120.

HESTER, A. J., 1988. Successional vegetational change: the effect of shading on Calluna vulgaris (L.) Hull.
Transactions of the Botanical Society of Edinburgh, 45: 121-126.

KEATINGE, T. H., 1975. Plant community dynamics in wet heathland. Journal of Ecology, 63: 163-172.

MALLIK, A. U., HOBBS, R. J. & LEGG, C., 1984. Seed dynamics in Calluna- Arctostaphylos heath in north¬
eastern Scotland. Journal of Ecology 72: 855-871.

MOHAMED, B. F. & GIMINGHAM, C. H., 1970. The morphology of vegetative regeneration in Calluna
vulgaris. New Phytologist, 69: 743-750.

NORDHAGEN, R., 1937. Studien iiber die monotypische Gattung Calluna Salisb. Bergens Museums Arbok, 1937.
naturvid. rekke, 4: 1-55.

SCANDRETT, E., 1987. Gap formation and cyclical change in heathland vegetation. Unpublished Ph.D. Thesis of the
University of Aberdeen.

WATT, A. S., 1947. Pattern and process in the plant community. Journal of Ecology, 35: 1-22.

WATT, A. S., 1955. Bracken versus heather: a study in plant sociology. Journal of Ecology, 43: 490—506.

WEBB, N., 1986. Heathlands. London: Collins.

Botanical Journal of the Linnean Society (1989), 101: 269-277.

Heathers in Ireland

E. CHARLES NELSON, F.L.S.

National Botanic Gardens, Glasnevin, Dublin 9, Republic of Ireland

NELSON, E. C., 1989. Heathers in Ireland.

ADDITIONAL KEY WORDS: — Calluna - Daboecia — Erica — Ericaceae.

CONTENTS

Introduction . 269

Daboecia . 270

Erica . 271

Calluna . 275

Conclusion . 275

References . 276

Gaily they grow, the quiet throng,

Fair gems of the realm of sun and wind
The hanging bells of the high crags,

Flowers of the rocks, like cups of honey.

Eihon Wyn (1867 1926).

INTRODUCTION

The poets of our Celtic past, word-smiths that have few modern equals, sang
praises to the wild flowers and the wildernesses in which they lived and
worshipped (Jackson, 1935; Heaney, 1982). They could not, and did not, ignore
such a prevalent plant as heather: “fair gems of the realm of sun and wind" is
apt as a metaphor for these shrubs.

Since early Christian times when men began to write words on vellum,
heather has been reported as a denizen of Ireland. The seventh century poet who
composed the Song of Marban, the hermit, was among the first (Nelson, 1979a):

I have a hut in the wood;

None knows it but my lord.

An ash tree this side, a hazel on the other,

A great fern makes the door.

Two heathery door-post for support,

A lintel of honeysuckle,

Around its close the wood
Sheds it nuts upon fat swine.

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E. C. NELSON

The heathers of Ireland were not merely sustenance for the poet's
imagination: they had mundane uses too; under the ancient Irish law code, the
Brehon Laws, heather was a protected plant codified as losa fedo bushes of the
wood) (Kelly, 1976); heather has been used to produce a yellow dye (Mahon,
1982). While not perhaps as widely utilized as, for example, gorse ( Ulex
europaeus L.), heather certainly was used to thatch boliehouses — the milking huts
in the summer pastures— and to make the two-ply ropes that were used to fix the
thatch to cabins (Evans, 1957). Flowering heather was a source of nectar for bees
(Watson, 1981).

Heather was, and is still a most familiar plant to most people in Ireland it
inhabits moorland and bog contributing to the formation of the peat, cut as turf,
which to this day is an indispensable indigenous fuel. But the familiar,
commonplace heather is not as well-known to scientists, I suggest, as might be
thought. There is much that is puzzling, even poetic, many questions that are
unanswered about the heathers that have colonized Ireland; in particular, we
continue to be puzzled by the imbalance, by the conundrum of species common
to Ireland and continental Europe but absent from Britain (Praeger, 1932;
Webb, 1972).

There are seven native genera of the Ericaceae in Ireland, and about fourteen
species recognized as indigenous, in addition there are a few naturalized aliens
(Scannell & Synnott, 1987). The ericaceous taxa not usually classified in the
folk-taxonomy as heathers are: Arbutus unedo L., Arctostaphyllos uva-ursi L.
Sprengel, 1 7 actinium myrtillush ., V. oxycoccus L., V. vitis-idaea L. and Andromeda
polifolia L. Rhododendron, Pernettya and Gaultheria are represented by naturalized
species. The three native "heather' genera are Calluna (represented by
C. vulgaris (L.) Hull), Erica (with six native species — E.erigena R. Ross,
E.cinerea L., E. vagans L., E. ciliaris L., E.tetralix L., E.mackaiana Bab.), and
Daboecia (represented by D.cantabrica (Huds.) Koch).

DABOECIA

Daboecia cantabrica is unquestionably the most beautiful, most spectacular of
the native heathers, its handsome "bells' are much larger than the flowers of any^
of the heathers native in Britain, and it forms a conspicuous component of the
vegetation of parts of Connemara (County Galway) and southern Mayo. Apart
from work for Atlas of the British Flora (Perring & Walters, 1962), no detailed
studies have been undertaken and published on its distribution in Ireland, and
no-one has defined the precise limits of its range. Why it should be confined to
the Connemara/south Mayo region (cf. Praeger, 1934) is not easy to explain, but
then the distribution of most of the indigenous heathers is peculiar. As difficult to
explain is the species’ absence from Britain. It does inhabit large tracts of south¬
western Europe, from central Portugal northwards into Galicia and thence
through northern Spain, the Pyrenees into western France and on the Azores
there is a population which is sometimes regarded as a separate species.

Daboecia cantabrica varies morphologically but within narrow limits. The more
remarkable wild variants are all now familiar garden plants — white-flowered
ones were reported in the early nineteenth century (Nelson, 1982) and the red-
flowered forms in the 1930s (Walsh, Ross & Nelson, 1983), and though not
common they are certainly not rare and in certain areas can be relatively easy to

HEATHERS IN IRELAND

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find. A 'double-flowered1 plant found in Connemara by the author has a
multitude of petaloid structures inside the corolla replacing the stamens, and a
series of 'inner corollas’ too; this is now in cultivation as D. cantabrica cv. Charles
Nelson (McClintock, 1983).

Daboecia has a unique connection with Ireland, for the generic name is a
misspelt version of the name of one of our ascetic saints. Dabeoc ( pronounced
Davock) of Lough Derg (County Donegal) certainly had nothing to do with this
heather and Linnaeus (1762), in coining the binomial Erica daboecii, based on the
polynomial Erica S[ancti] Dabeoci Hibernis, itself a Latin translation of the Irish
frych Dabeog recorded by the Welsh antiquarian and natural historian Edward
Lhuyd in 1700, haphazardly reversed the “o” and “e” (cf. Nelson, 1985). Thus
we have a name that is unpronounceable gibberish.

Daboecia cantabrica is one of the heathers that contributes to the patchwork of
purple and gold which colours the August landscape in Connemara; purple is
also provided by Erica cinerea, and gold is the gorse (Ulex gallii Planchon;
(Praeger, 1934). Daboecia cantabrica and E. cinerea tend to prefer well-drained,
acidic habitats — they are not plants of the dampest boglands where E. tetralix is
prevalent.

ERICA

Erica tetralix is perhaps not as interesting as some of the rarer species; it is
ubiquitous throughout Ireland in suitable habitats, easily identified by its
densely hirsute ovary, and while occasional strange variants are recorded for
example, one with glabrous foliage and a sparsely hirsute ovary about north
Mayo (reported as Erica x stuartii ( = E. x praegeri.); cf. Lamb, 1964), and
prostrate coastal forms — little attention has been paid to morphological
variation patterns in this species’ Irish populations. Casual observations suggest
that it reproduces and spreads principally by seed; seedlings occur most
frequently in burnt areas. Vegetative reproduction is rarely observed;
infrequently is there regeneration from old rootstocks, so no tufts are seen on the
vertical faces of disused turf-banks. This is in sharp contrast to another species,
sometimes regarded as a mere sub-species of E. tetralix, but one certainly
deserving full specific rank, namely E. mackaiana.

Erica mackaiana is one of the three heathers found in Ireland and western
Europe but not in Britain. Some of its habitats in northern Spain (Nelson &
Fraga, 1984; Fraga, 1984) are remarkably like those which it frequents in
western Ireland, but this is a superficial judgement based on a brief visit some
years ago. In other Spanish haunts it hugs pine wood margins, a habitat not
present on the bogs of Connemara and Donegal at the present time.

Quite a lot has been written about this species which is today the least
contentious; for example, it was suggested that a single clone was present about
Craiggamore in Connemara (McClintock, 1972; Scannell & McClintock, 1974).
Again, even casual observations made in the region will reveal several different
‘types’, with distinct corolla shapes, sizes and colour-shades. The Craiggamore
populations have been sampled and plants, propagated from these, have been
cultivated together under a uniform regime at the National Botanic Gardens,
Glasnevin, for seven years; the morphological differences observed in the held

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E. C. NELSON

persist, and can be quantified. Corolla shape, size and shade are not the only
characters which vary — plants have different habits and other distinctive traits
could be studied under garden regimes.

One of the most enigmatic characteristics of the Irish populations is their
apparent sterility (Webb, 1972). In Spain seed is abundant and seedlings are
frequent. Under cultivation at Glasnevin, I have found that Irish plants are not
fertile, while the Spanish plants can have swollen, seed-laden ovaries. No
adequate explanation of this phenomenon has been attempted, because no
comparative research has been carried out into the reproductive biology of these
plants. A study in progress on the reproductive strategies of Erica mackaiana and
E. tetralix in Connemara, especially their respective abilities to spread by
vegetative means, may begin to help us understand the enigma.

Another casual observation which had not been subjected to detailed study is
the frequent occurrence of malformed stamens, styles and stigmas in the flowers
of Irish Erica mackaiana. The extreme example is the well-known cutivar
E. mackaiana 'Plena' in which all the reproductive organs have been replaced
with petaloid bracts. Plants with lesser malformations, ranging from fused
filaments (forming a ‘second corolla') to slightly broadened filaments, and
sometimes with enlarged or truncated styles are often found when random
population samples of E. mackaiana are studied. I have no precise figures for the
prevalence of this syndrome of malformations, but it is present in the two
separate Connemara populations [fide specimens in DBN); there is no evidence
for it occurring in Donegal.

As far as the ecology of Erica mackaiana is concerned, nothing useful can be
added to the information given by Webb (1955) in his biological flora. Erica
mackaiana is frequent around lough margins and on cutaways in peatlands; the
study in progress will enlarge our store of knowledge about the relative
distribution patterns of this species and its close relative, E. tetralix, at least in the
principal Connemara locations. Erica mackaiana is now known to be more
widespread than early accounts suggested; the Connemara population has been
mapped and it extends from Errisbeg north towards Clifden (Nelson, 1981a).
The Carna population was lost and then found again, while the Donegal one is,
as recorded by Webb (1954), confined to the immediate environs of Upper
Tough Nacung.

Since the beginning of this century, it has been recognized that Erica mackaiana
and E. tetralix cross-pollinate in Ireland, and the siblings of this marriage are now
named E.xstuartii (MacFarlane) Linton (formerly familar as E.xpraegeri
Ostenf. ) (McClintock, 1979, 1980). This hybrid is abundant in the three Irish
stations, but it has not been reported in Spain, even where the two species are
sympatric although such a situation is extremely rare (Nelson & Fraga, 1984;
Fraga, 1984). Erica mackaiana totally displaces E. tetralix in the relatively cool, wet
habitats on the northern and western sides of the Cantabrian mountains, and
during field-work in Spain only four sites were discovered where E. mackaiana
and E. tetralix grew together (Nelson & Fraga, 1984).

In Ireland, given the inability of Erica mackaiana to produce seed, except
perhaps very infrequently, this hybrid must result from the pollination of
E. tetralix. Hybrid plants may not be entirely sterile — either a few are capable of
producing seed, or some pollen grains are viable — for a swarm in intermediates

HEATHERS IN IRELAND

273

between E. tetralix and E. x stuartii has been collected in Connemara, there is
almost a continuum in some areas with plants grading from the typical E. tetralix
(with a hirsute ovary) to plants with a scarcely pubescent ovary. Webb &
Scanned (1983) stated that no back-crossing appears to take place, but my
observations suggest that back-crossing (at least against E. tetralix) must occur,
perhaps frequently. In E. mackaiana the ovary is completely devoid of hairs, and a
few intermediates have been collected with a few hairs at the summit of the
ovary, again suggesting back-crossing against it; these observations have not yet
been quantified.

Within the area inhabited by Erica mackaiana and E. x stuartii in Connemara
there are more species of heather to be collected than in any other place in these
islands. The heather flora includes the rarest of the indigenous species, E. ciliaris,
Dorset Heath.

Erica ciliaris is restricted to a small patch beside the road between Clifden and
Roundstone where it was first discovered in 1846 (Eager, Nelson & Scanned,
1978). Whether the present minute population is the ‘original1 one is often
discussed and the likelihood is that it is.

In Ireland Erica ciliaris is eglandular (McClintock, 1968)— I think it likely
that the half-dozen or so clumps which exist represent a clone, so the uniformity
is not inexplicable. Furthermore, while a few dowers may be seen in August, the
peak of flowering does not occur until late September and the plants continue in
bloom through the autumn (Nelson, 1983). Under the climatic regime of
western Connemara it is unlikely that E. ciliaris has any opportunity to set viable
seed in Ireland and the survival of the populations is thus dependent upon its
ability to reproduce vegetatively by layering.

As pointed out by Webb (1966) the Irish habitat differs from that occupied by
this species in Britain and on the continent where Erica ciliaris colonizes 'dry
heaths’. In Ireland it grows in a damp hollow although remarkably the best
growth is immediately adjacent to the road-filling. The plant is protected by law,
although that cannot prevent natural predation by wild animals (Nelson, 1986).

Not as rare, but hardly less puzzling, is Erica vagans, Cornish Heath, which has
had a chequered history in Ireland being reported from County Waterford early
last century, then becoming ‘lost’, and rediscovered in County Fermanagh in the
1930s (Praeger, 1938, 1946): the Waterford report was always suspicious and
may now be discounted as a phantom; the Fermanagh population is thriving.
On a moorland site at Carrickbrawn — the rock of sorrows — E. vagans grows on a
gently sloping hillside not far from a small mountain stream. Its habitat was
intensively sampled and a detailed vegetation survey underpinned by soil
analyses was carried out in the summer of 1970 (Nelson & Coker, 1974). To
summarize those results, the heather was confined to an area through which
percolated water enriched with dissolved minerals; significantly higher
concentrations of calcium and other bases were recorded within the colony
suggesting that E. vagans grows there because of a less acidic, nutrient-rich soil.
The Carrickbrawn population is uniform in flower colour, white — the pinks and
lavender shades seen in Cornwall are absent — so the present population may be
a clone although seedlings have been seen in one area.

The principal question still posed by this population is whether it is native or
introduced. On the whole, I adhere to the view that it is an indigenous

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population, not introduced in recent times, but perhaps sometime, long ago, it
was assisted by man to colonize Ireland (Nelson & Coker, 1974). I do not believe
Cornish Heath was deliberately planted at Carrickbrawn: that is the most
improbable of the improbabilities.

H uman influence on the composition of the present flora of Ireland has been
considerable, but botanists have generally been reluctant to proclaim plants as
exotic imports without good historical evidence. Recent remarkable finds, of
which Juncus planifolius R. Br. (cf. Webb & Scanned, 1983) and Haloragis
micrantha (Thunb.) Sieb & Zucc. (Green, 1989) are the most celebrated, do
indicate that plants can arrive and may flourish unnoticed, spreading rapidly
and ousting native species. That particular rush is now found in substantial
quantities in Connemara and doubtless its conquest of Ireland is only beginning.

Erica erigena, Irish Heath, is one of the most perplexing plants in the heather
flora. It is sometimes described as rare, but its populations range over thousands
of hectares of moorland and mountain, generally where there is moving water,
although it will grow almost totally submerged in bogs (Foss, Doyle & Nelson,
1987). This species is apparently spreading, occupying new habitats, but not
ranging far outside those places whence it has been reported for more than 50
years; the species’ distribution in Ireland has been mapped recently, and all the
populations previously reported — for example by Robert Lloyd Praeger — were
relocated (Foss, Doyle & Nelson, 1987). In the last few years E. erigena has been
studied by Foss (cf. Foss & Doyle, 1988), and he has answered some questions
and provokingly suggested that this is an introduced plant, perhaps brought to
Ireland in the fifteenth century from north-western Spain, maybe as packing
material for wine-flasks. Pollen profiles from sites now profusely covered with
E. erigena had its pollen only in the upper levels. In striking contrast to
E. mackaiana , pollen of this species is not known from Irish sites in the pre-
Christian period (cf. Mitchell & Watts, 1970).

Erica erigena is an opportunist: it has colonized old railway embankments in
Mayo; it occurs on lazy beds — derelict potato fields abandoned perhaps 150
years ago — on the slopes of Mweelrea; it grows on cut-over bogs throughout
Mayo; and inhabits stream banks and lough shores. It reproduces by seed and
there is a range of colour forms from pallid cream pinks to dark lavenders and
even some with clear pink (Walsh & Nelson, 1988).

In many ways this is a plant that is out of place, spectacularly so, as it blooms
in early spring when few other indigenous species are in flower. It is tolerant of
salty winds but not so tolerant of heavy frosts, and thus tends to inhabit coastal
areas.

Erica cinerea is the last of the indigenous species. Like E. tetralix it occurs
throughout the island in suitable habitats. Like E. tetralix it apparently displays
little morphological variation: yet prostrate forms do occur in coastal areas and
occasionally white-flowered plants are noticed. Red (not purple) blossomed
variants are occasionally reported.

This plant behaves in Ireland as would be expected, frequenting well-drained,
acidic habitats. In Connemara it grows on rocky outcrops where there is a
shallow peaty soil, associated often — as I have noted — with Ulex gallii and
Daboecia cantabrica (Praeger, 1934). Calluna vulgaris will also occur in similar
situations.

HEATHERS IN IRELAND

275

CALLUNA

Calluna vulgaris, ling or fraoch, is undoubtedly the most abundant of the
heathers in Ireland, occupying vast tracts of heathland and peat-bog. It shows
relatively little variation in morphology although prostrate variants have been
collected in extreme coastal sites. Flower colour ranges within the same band as
in Britain and other parts of Europe white-flowered plants are relatively
infrequent and nowhere dominant. From one wild locality, in the early 1930s, a
multi-petalled form was gathered and it survives in cultivation as C. vulgaris cv.
County Wicklow (Nelson, 1981).

This is a plant with a wide tolerance of habitats, from windswept mountain
tops to sheltered woodland margins, from sodden peat bogs to apparently well-
drained rocky hillsides. There is one habitat in Ireland which perhaps few would
immediately regard as a suitable one for Calluna, yet in it Calluna is not just
frequent, it is ubiquitous. The Burren, County Clare, is the archetypal karst
landscape in these islands, with limestone pavements and a flora that is usually
characterized as calcicole — Gentiana vernah ., Dryas octopetalah. and a host of
other lime-tolerant species abound. But again, the casual botanical visitor to The
Burren must surely be impressed and intrigued by the presence on the limestone
pavements of the heathers, both Calluna vulgaris and Erica cinerea abound on the
little ‘islands’ of peaty soil which rest on the rock, and are often thereon
associated with Arctostaphylos uva-ursi and Empetrum nigrum L. (Webb, 1962; Webb
& Scanned, 1983). Narthecium ossijragum T., a distinctly calcifugous species, was
added recently (Nelson, 1989) to the flora of The Burren hills. Ivimey-Cook &
Proctor (1966) noted the presence of Calluna vulgaris and Erica cinerea in several
associations, and described the progression from species communities typical of
calcareous grasslands ( Dryas octopetala Hypericum pulchrum L. association, for
example) through to heather dominated tussocks growing in highly leached soil,
the acidity of which was enhanced by the accumulated organic material derived
from the heathers. To see Calluna and Erica cinerea plants apparently thriving on
limestone pavement is a weird experience which would surely repay detailed
study with modern electronic environmental monitors — Ivimey-Cook & Proctor
(1966) only set out to describe and classify species associations and did not
provide environmental data. To any botanist wanting to see Calluna in Ireland, I
would now say that The Burren is one of the best sites — it certainly provides the
most provocative situations.

CONCLUSION

Those are the Irish heathers, a group of plants with different ecological
propensities and distinctive distribution patterns. They continue to perplex plant
geographers. It has been suggested that the so-called “Lusitaniaff
species — Erica mackaiana, E. erigena, E. ciliaris, E. vagans, Daboecia cantabrica and
Arbutus unedo — survived in some refugium on the continental shell through the
last glacial period, and that when the climate ameliorated they recolonized the
lands vacated by ice and tundra (Mitchell & Watts, 1970). Such an hypothesis is
now regarded as untenable — ocean current patterns changed during the glacial
periods (Ruddimann & McIntyre, 1973; Ruddimann, Sancetta & McIntyre,

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E. C. NELSON

1977) and the western coastline of northern Europe was not bathed in warm
water as it is today. For such frost-sensitive plants to have survived hundreds of
thousands of years in any refuge to the west is most unlikely (Watts, 1977;
Nelson, 1979b). And there is then another problem: if these plants migrated by
way of a landbridge, could they have reached Ireland from Europe before sea-
levels swamped the migration route (cf. Nelson, 1979b; Devoy, 1985)? The
answer is likely to be ‘No1 (cf. Moore, 1987).

There is a long way yet to go, I suggest, before we can be certain that each
species within this group of Irish plants has a common history. The arguments
presented by Foss (Foss & Doyle, 1988) for Erica erigena are persuasive, and while
I would not suggest that E. mackaiana and Daboecia cantabrica were brought to
Ireland by man, we may keep an open mind about the historical biogeography
of these taxa.

Heathers have been an integral part of Irish life for centuries: they have
provided bedding for humans and fodder for domestic stock, ready-made whisks
for spraying potatoes (cf. Scanned, 1983), thatch for houses, tinder for fire; they
have yielded dyes, and honey. Today the heathers have lost most of their
mundane uses being replaced by modern fabricated materials and tools, but the
poetry remains; the tourist brochures proclaim purple mountains cloaked with
heather and the purple prose of advertising agencies trumpets blended liqueurs
as ‘a classic marriage of heather and honey, exotic herbs and Irish spirits’.

For botanists there is much yet to be discovered about these plants, and the
unravelling of the contradictions that characterize the Irish heather flora should
provide much to stimulate active minds for many years to come.

And, of course, we plant heathers in our gardens (Nelson, 1984) to brighten
the summer.

Summer brings low the little stream,

The swift herd makes of the water
The long hair of the heather spreads out,

The weak white cotton-grass flourishes. . .

Flowers cover the world.

Anonymous, c. 900 AD

REFERENCES

DEVOY, R. J., 1985. T he problem of a late Quaternary landbridge between Britain and Ireland. Quaternary
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EAGER, A. R., NELSON, E. C. & SCANNELL, M. J. P., 1978. Erica cilians L. in Connemara, 1846-1853.
Irish Naturalists Journal, 19: 244-245.

EVANS, E. E., 1957. Irish Folk Ways. London: Routledge & Kegan Paul.

FOSS, P. J. & DOYLE, G. J., 1988. Why has Erica erigena (the Irish heather) such a markedly disjunct
European distribution? Plants Today, 1: 161-168.

FOSS, P. J. DOYLE, G. J. & NELSON, E. C., 1987. The distribution of Erica erigena R. Ross in Ireland.
Wat sonia, 16: 311-327.

FRAGA, M. I., 1984. Notes on the morphology and distribution o {Erica and Calluna in Galicia, north-western
Spain. Glasra, 7: 1 1-23.

GREEN, P., 1989. Haloragis micrantha — creeping raspwort. B.S.B.I. News, 51: 48.

HEANEY, S., 1982. The god in the tree. In S. Mac Reamoinn (Ed.), The Pleasures of Gaelic Poetry. London:
Allen Lane.

IVIMEY-COOK, R. B. & PROCTOR, M. C. F., 1966. The plant communities of the Burren, County Clare.

Proceedings of the Royal Irish Academy, 64 B: 21 1-301.

JACKSON, K., 1935. Studies in Early Celtic Nature Poetry. Cambridge: Cambridge Lmiversity Press.

KELLY, F., 1976. The old Irish tree-list. Celtica, 11: 107-124.

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LAMB, J. G. D., 1964. On the probable occurrence of Erica mackaiana Bab. in County Mayo. Irish Naturalists’
Journal, 14: 213-214.

LINNAEUS, C., 1762. Species Plantarum. Edition 2.

McCLINTOCK, D., 1968. Further notes on Erica ciliaris in Ireland. Proceedings of the Botanical Society of the
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McCLINTOCK, D., 1972. Wild heathers of Ireland. In [Report of the] Recorders’ Conference, Dublin 1972.
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McCLINTOCK, D., 1979. The status of, and correct name for, Erica ‘ Stuartii ’ . Watsonia, 12: 249-252.

McCLINTOCK, E., 1980. Erica x stuartii E. F. Linton— a correction. Watsonia, 13: 59.

McCLINTOCK, D., 1983. A double form of Daboecia cantabrica. Year Book of the Heather Society, 1982: 32-33.

MAHON, B., 1982. Traditional dyestuffs of Ireland. In A. Gailey & D. O. Hogain (Eds), Gold under Furze.
Studies in Folk Tradition. Dublin: Glendale Press.

MITCHELL, G. F. & WATTS, W. A., 1970. The history of the Ericaceae in Ireland during the Quaternary
epoch. In D. Walker & R. G. West (Eds), Studies in the Vegetational History of the British Isles. Cambridge:
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MOORE, P. D., 1987. Snails and the Irish question. Nature, 328: 381-382.

NELSON, E. C., 1979a. Historical records of the Irish Ericaceae, with particular reference to the discovery
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NELSON, E. C., 1981b. The origin of Calluna vulgaris cv. County Wicklow. Irish Naturalists’ Journal, 20: 212.

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WEBB, D. A., 1962. Noteworthy plants of the Burren: a catalogue raisonne. Procedings of the Royal Irish Academy,
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WEBB, D. A., 1966. Erica ciliaris L. in Ireland. Procedings of the Botanical Society of the British Isles, 6: 221-225.

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Botanical Journal of the Linnean Society (1989), 101: 279-289.

The heathers of Europe and adjacent areas

DAVID McCLINTOCK, F.L.S.

Bracken Hill, Platt, Sevenoaks, Kent, TN15 8JH

McCLINTOCK, D., 1989. The heathers of Europe and adjacent areas. Andromeda polifolia,
Bruckenthalia spiculifolia, Calluna vulgaris, two species of Daboecia, 19 of Erica with five subspecies and
seven natural hybrids are discussed. Comment is chiefly given on E. andevalensis, E. maderensis and the
group currently denominated: E. anthura, E. manipuliflora, E. multiflora and E. vagans. Two new
combinations are made.

ADDITIONAL KEY WORDS:- -Andromeda - Calluna - Daboecia - Erica - Ericaceae - hybrids.

CONTENTS

Introduction . 279

The heathers . 280

Daboecia . 280

Andromeda . 280

Calluna . 281

Erica . 281

Hybrids between Erica species in different sections . 287

Bruckenthalia . 288

References . 288

INTRODUCTION

The ‘adjacent areas' discussed in this paper extend from N. America to
Siberia, Japan and the Levant in Asia, to Madeira and N. Africa and, for one
species, to south of the equator. In this extensive domain, some 36 apparently
distinct species, subspecies and hybrids have had their origin and been named,
with further hybrids so far unnamed.

Three general comments should be made.

1. Chromosomes. Of these 36, and, of the many hundreds of species in
southern Africa, only 24 have ever had their chromosome number ascertained,
and five of these are horticultural hybrids of South African species. Only seven
plants of British origin have ever been counted (McClintock, 1979; Brandham &
McClintock, 1983; Fraga, 1983). The numbers are Calluna 2 n— 16, Daboecia and
Erica 2^ = 24, Bruckenthalia 2^ = 36 — a polyploid?, while Andromeda (including its
North American variant, glaucophylla) has 2^ = 48 and must surely be a
polyploid.

2. Until very recently, the thousands of hardy cultivars grown were all
completely natural seedlings or sports unaided by man, who did no more than
propagate them. Thus, they demonstrate the extent of the genetic store of the
taxa in question, in a way no wild population can. The reason for this is that

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D. McCLINTOCK

many of the garden variants lack the robustness or other abilities to compete
with more normally adapted plants; for example, plants with yellow foliage, or
otherwise masked chlorophyll, are inevitably less vigorous. One is more likely to
come across worthwhile variant seedlings on open ground, such as the edges of
newly made roads before competition closes in on them. Furthermore, sports are
practically incapable of perpetuating themselves, but for a gardener propagation
is simple.

3. Attempts have been made on a small scale to produce a key to cultivars, a
desirable objective, e.g. Munson, 1984. This is made easier if they can be
grouped under some botanical category (since all are basically natural products;
which will also cover wild, not yet cultivated, plants (McClintock, 1986;. To cite
just one example, plants of Erica tetralix L, with untypical racemose inflorescences
instead of the usual umbel, have been grouped under forma racemosa
(McClintock, 1982). The cultivar ‘Terschelling’ fits in here and is the type of this
form, of which other unnamed examples exist in herbaria. To have a cultivar as
the type makes access to it much easier.

The taxa below are set out in taxonomic sequence, the Ericas alphabetically in
their sections.

THE HEATHERS
Daboecia

Three aberrations may be briefly mentioned. Daboecia cantabrica (Hudson) C.
Koch ‘Covadonga' has its corolla divided into four, giving it a very different
appearance — it came from Asturias, Spain. ‘Charles Nelson' from W. Ireland
has, basically, double flowers. But these flowers have a curious characteristic in
that the first, often all those on the plant, are single, as are occasionally the last
ones. "Bicolor' known in gardens for over a century, a chimaera, with flowers of
every combination of purple and white, has produced identical seedlings. All
come under var. bicolor Dippel.

Daboecia azorica Tutin & E. F. Warburg. This differs morphologically only in
the smaller size of its parts and the absence of hairs on the corolla (the hairs are
present but can be very hard to find in D . cantabrica) . It reaches a far greater
altitude, carpeting the ground almost to the summit of Pico at 2320 m (Richards,
1976). Pressing personal wishes to the contrary by both the authors of this name
previously inhibited me from altering its status. But it does seem that it should be
recognized at no more than subspecific level, this specially in view of its
markedly distinct distribution — for the hybrids between the two species D. scotica
D. McClintock, are fully fertile and backcross readily. They are markedly
hardier than either parent.

So, Daboecia cantabrica (Hudson) C. Koch subsp. azorica (Tutin & E. F.

Warburg) D. McClintock, stat. nov.
basionym: D. azorica Tutin & E. F. Warburg, Bot.J., 70: 12 (193 2).

Andromeda

Not everyone accepts this as a heather, but it was considered so when the
Heather Society was made International Registrar for heathers in 1969.

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281

This almost circumpolar plant changes little through its immense range.
Certain plants in N. America are generally cited as A. glaucophylla Link. Their
characteristics, however, are to be found in varying degree in plants named
A. polifolia, which also occurs widely in N. America. Varietal status seems the
most that these variants merit.

An odd fact is that white-flowered plants seem to be unknown in Europe.
They are mentioned for A. glaucophylla in N. America, but I have never seen any
from there. All the white-flowered plants grown in gardens come from Japan.

Calluna

Scores of infraspecific names have been published (cf. Beijerinck, 1940 ). The
most used is var. hirsuta S. F. Gray (predated by var. hirsuta Waitz), but opinions
vary as to where the dividing line comes between the extremes of glabrous and
shaggy plants.

Lmambiguous is var. multibracteata J. Jansen. There are two groups of very
late-flowering Lings. The earlier has normal bracts; the later numerous bracts,
which pile up until finally, weather permitting, a flower appears. This clearly
separates such plants in both gardens and the wild (Turpin, 1984).

Plants occur with flowers that never open (Turpin, 1980). There are three
reasons for this, and names to match, again an essential way of sorting such
occurrences. In f. clistanthes J. Jansen, the flowers are normal but the style
becomes stunted. In the commonest variant f. diplocalyx J. Jansen, the plants have
no stamens or corolla, but eight sepals, twice the normal number. Forma
polysepala W. Beijerinck also lacks stamens and corolla, but has more than eight
sepals and usually a deformed style and stigma.

Two other features of this species may be mentioned. Two double whites 'Alba
Plena1 and ‘Else Frye' have totally different origins. The former was a sport on a
white-flowered plant on a North German moor in 1934, the latter a sport on a
pink-flowered plant in Seattle N.W. America in the 1940s — before ‘Alba Plena’
ever reached that country. Yet the two are indistinguishable. In both double
whites some of the lower florets are single and likely to be the source of similar
double seedlings that have been found near by.

Finally, on exposed cliffs, e.g. in S.W. Ireland and N.W. Scotland including St
Kilda (Brien, 1974), the plants are genetically prostrate. This is an example of
outside influences selecting the genes. In some of these areas the majority of these
plants have white flowers (Scully, 1916), a fact not yet explained.

Erica

Erica andevalensis Cabezudo & Rivera

The plants long recorded from the Huelva region of S.W. Spain as E. tetralix
do not belong to that species. In 1980 the name E. andevalensis was published for
them. Their close similarity to E. mackaiana Babington was noted, from which
they were differentiated only by having shorter glandular hairs. They even share
the tiny knob at the base of the anther opposite the appendage, a feature noted
by Mr E. G. H. Oliver. Erica andevalensis attains 1 m, bushily, with stout stems, in
much the same manner as E. mackaiana usually grows in the north of Spain.
Their very remarkable habitat as given by these authors was 'flas escombreras y
alrededores de las minas de pirita”, and indeed they grow where no other plants

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D. McCLINTOCK

can but, it seems that the authors did not look in any more natural habitats.
However, in 1982 specimens were found in quantity along stretches of the River
Odiel near by — where the water was also contaminated; consequently here too
the lowest zone of vegetation consisted solely of this species (Nelson, McClintock
& Small, 1985).

What status should these have? Glands alone are not enough to justify a
distinct species, all the more because at least one plant was found in 1982 with no
glands at all (McClintock, 1983a: 36) (a state paralleled in E. mackaiana ,
McClintock, 1983b). ‘Lawsoniana’ and its white sport ‘Dr Ronald Gray' are also
eglandular. Because of its very disjunct area and fantastic habitat, subspecific
rank seems the most that can be justified, for this species:

Erica mackaiana Babington sufosp. andevalensis (Cabezudo & Rivera) D.

McClintock & E. C. Nelson, stat. nov.

basionym: E. andevalensis Cabezudo & Rivera, Lagascalia, 9(2): 223 226 ( 1980).
E. australis L.

A gay species calling for little comment. At one time rather smaller plants
from the north of the peninsula were given specific rank as E. aragonensis.
However, they really differ only in size from typical plants and are at best
denominated var. aragonensis (Willkomm & Lange) P. Coutinho.

E. cinerea L.

This species, whose easterly limits just reach into W. Italy, S. Holland,
W. Germany, and S.W. Norway, has the greatest range of flower colour of any
heather of the N. hemisphere — reds and pinks in almost every conceivable hue
from palest mauve to dark beetroot, plus whites, and bicolors.

There is a variant, var. schizopetala Boulger, in which the corolla is evenly
divided into four segments. Not only can this come true from seed, but it has also
been found as a sport on ‘C. G. Best’, in cultivation as ‘Yvonne’ (McClintock,
1980a). ‘C. G. Best' itself is remarkable in frequently producing seedlings of the
same flower colour.

E. mackaiana Babington

This perplexing taxon grows in three distinct areas: Co. Donegal in
N.W. Ireland, 180 miles further south in Connemara, Co. Galway, and 750 miles
further south still, in Asturias, Spain (where it was first found in the same year,
1835, as in Connemara), where it is now known to extend for nearly 300 km east
to west (Nelson & Fraga, 1983). In Connemara it is almost sterile, in Spain
fertile. Other differences between these two colonies are difficult to find, apart
from the fact that most plants in Spain grow taller and stouter. Plants in the
colony in N.W. Ireland are markedly larger than those in Connemara, but never
as tall as most Spanish plants.

Two variants, both from Connemara, may be mentioned. The fully double
‘Plena’ has been collected, possibly in the same site each time (but efforts to
refind it, even with directions, have failed) in 1869, 1901 (when is was called
E. crawfordii) , 1965 and 1970. No other double hardy Erica is known, and only
very few, non-persistent, South African examples. The other variant, in
cultivation as ‘Maura’, has semi-double flowers. These can vary so much that
Turpin (personal communication) found the 12 florets on one stem each to differ

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283

significantly from the others. Similar variations in an inflorescence have been
found on other species.

E. maderensis (Bentham) Bornmuller

This is endemic to Madeira. At lower altitudes, such as 1000 m, it forms a
stout bushy plant 60 cm high or so (Richards, 1976); on exposed rocks at the
summit of Pico Ruivo — 1863 m, it forms cushions or mats, clearly of considerable
age — the species may be a poor competitor.

This used to be considered a variety of E. cinerea (the record for which species
in Madeira is erroneous) but it differs markedly in its habit and in the fact that
its leaves in threes never develop into fascicles as do those of E. cinerea. The
distinctions are set out by McClintock (1981). Ranking this as a good species is
justified.

E. terminalis Salisb.

Briquet & Litardiere (1938), as do most authors, give the height of this central
Mediterranean species as 0.5-1.0m, but in 1988 I saw it in Corsica with 2.8 m
stems, as indeed it can have in Britain, a true stout tree heath. This was on a
search for a white-flowered plant, f. albiflora Litardiere, greatly desired in
gardens, and not on record since 1847. It is the only known species with free
pollen grains; all the others have tetrads.

E. tetralix L.

This is widespread, petering out east in the Eastern Baltic, but does not grow
further south than N. Spain. The type is glandular (McClintock, 1980b), but
since glandular and eglandular plants grow side by side, both flourishing, one
wonders what the value of glands is.

On moors in early summer it is not rare to find plants with corollas tattered in
a way which suggests mite damage. They have been named var. fissa Druce.
Despite specialists having searched over many years, no direct evidence of mites
has been discovered. Later in the year the damage ceases and the corollas are
intact.

E. x stuartii E. F. Linton [E. x praegeri Ostenfeld )

This is an unfortunate example of a name given originally to an extreme
aberration having to be applied to all forms of the taxon (McClintock, 1980d ).
The clone "Stuartii1 has highly distinctive, very narrow, small dark corollas,
quite unlike the usual normal-shaped pink corollas of this intermediate between
E. mackaiana and E. tetralix. Such plants are almost entirely sterile.

In 1980 Charles Nelson and I collected cuttings in Connemara from numerous
examples of E. mackaiana, E. x stuartii and E. tetralix with varying amounts of
glands and pubescence on the leaves and ovary. These, grown on at Glasnevin,
differed also in height, habit, flower colour and flowering time. Indeed, when
these have been fully worked on, they may well show almost every intermediate
and combination of characters between the glabrous-ovaried E. mackaiana and
the hairy E. tetralix (Nelson, 1989).

In assessing the populations of this group of species, from Southern Spain
northwards, wise folk have pondered how to account for their "distribution’,
notably for E. mackaiana. To me it is not distribution, but parallel evolution

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D. McCLINTOCK

(McClintock, 1983a: 38). I take E.tetralix as the eotaxon, whose genes have
combined similarly to produce similar plants in well-separated areas. Since then,
the variation has developed naturally by further genetic combination,
hybridization and local adaptation. That some of the resultant plants are sterile
is no bar to this theory, for there are many examples of sterile forms of good
species, not only among heathers. The late Dr C. West agreed that there were
similar likely causes to explain apparently identical taxa of Hieracium occurring
in widely separated areas with no obvious connections. There are analogies
elsewhere, such as the double white Calluna variants above and single white
E. x darleyensis below.

The state of affairs has been met by treating the group as consisting of
subspecies (Syme, 1872; Macfarlane, 1893), e.g. E.tetralix subsp. tetralix; subsp.
mackaiana (Babington) Syme (subsp. mackayi (Hooker) Macfarlane); with
possibly E. x stuartii and E. x andevalensis.

The alternative is to group together the taxa with at least some hairs on the
ovary, E. tetralix and E. x stuartii, and those with none, E. mackaiana and
E. andevalensis — as was proposed under E. andevalensis above.

E. arborea L.

This species extends further than any other heather, from the Atlantic islands
to the Caucasus and down through the Sahara as far as North of Lake Nyassa
9 JN 10"S, well south of the equator. In this vast range, dozens of infraspecific
names have been published but practically none seem to be of much taxonomic
value. The only infraspecihc name for any heath in the Mediterranean Check
List (Greuter, Burdet & Long, 1986) subsp. riojana (Sennen & Elias) Romo was
originally given specific rank. Its final character is “Foliis post desicationem
persistentibus”. The type is at BM and has no leaves at all. Better is var. alpina
Dieck, an entity which has not been evaluated in the held. ‘Alpina' from this
population has been grown in our gardens since the end of the last century. This
differs in habit, is later flowering, etc. (Turpin, 1981) but its special virtue is
greater hardiness, a merit inherited in its superb golden sport ‘Albert’s Gold'.
Pink Bowers are mentioned in numerous works, but I have vet to see such a
plant. In the Mediterranean area it reaches perhaps 5.5 m, but in Ethiopia and
East Africa, where it grows up to 4260 m altitude, its dimensions are far greater,
fully tree-size in trunk and height; while in the Atlantic islands it can be greater
still, up to 20 m, so far as my records go.

E. lusitanica Rudolph

This is indeed a Lusitanian species, one showing little variation, but the
yellow-foliaged "George Hurst’ is markedly tender. In the latter years the species
has made itself at home in three areas in S.W. England, and in Brittany. In New
Zealand it is a notifiable weed.

E. x veitchii Bean (E. arborea L. x E. lusitanica Rudolph)

Although there is an allusion to intermediates in Spain in the last century
Laguna, 1890) the two parent species so rarely grow in proximity that a wild
hybrid must be a rarity. Hybrids should be looked for where the two species
grow on Picoto in the Serra de Monchique, and also where they may meet in
N.W. Huelva (B. E. Smythies, personal communication). However, in gardens a

THE HEATHERS OF EUROPE AND ADJACENT AREAS

285

few examples have arisen (Turpin, 1979), the first in the Veitch nursery at
Exeter at the end of the last century. Most of these hybrids are more tender than
either parent; all have very low or no fertility.

E. carnea L.

The case for the retention of this familiar name appeared in 1987 fBrickell &
McClintock, 1987) and has since been recommended for acceptance at the next
International Botanical Congress (Brummitt, personal communication;.
Meanwhile, E. herbacea crept in, used by those unaware of the caveats set out by
Ross (1967:68). This is a plant of alkaline areas on the central European
mountains. Over 150 cultivars have been named and it is estimated that some
15-20 million plants are sold every year (Brickell & McClintock, 1987). Some
are perplexing, such as the largely sterile 'Eileen Porter’. Certain cultivars get
pineapple galls, others growing cheek by jowl do not, a useful distinction when
selecting garden plants. Yet I have found no record of the galls on wild plants
and galls are rare in Britain on any species.

E. erigena R. Ross

Had Rule 69 of the International Code of Botanical Nomenclature made at
the last International Botanical Congress existed earlier, it would not have been
necessary to disturb the name E. mediterrcinea which had been used
unambiguously for this species for nearly 200 years.

This species differs from E. carnea in effect only in its natural distribution the
largest colonies are probably those in W. Ireland (Foss, Doyle & Nelson, 1987 )
and in its height — it has attained almost 4 m, with support, in my own garden.
All the other published characters fail, and it is almost impossible to say to which
species a young plant belongs. Characters used have included infra-foliar ridges
(which rarely seems to work), flowering time (but E. erigena can flower before
E. carnea), length of inflorescence (said to be shorter in E. erigena, but 'Brian
Proudley’ can have inflorescences 30 cm long) and so on. An anomalous, much
compacter white cultivar ‘W. T. RacklifT is largely sterile and is in need of
investigation.

In view of this similarity, it must be doubtful if E. erigena should be regarded as
a distinct species; and indeed it has been recognized as E. carnea L. subsp.
occidentalis (Bentham) Lainz. The contrary view is based on the fact that
practically all the hybrids between the two species are sterile.

E. x darleyensis Bean

Because the natural distributions of the parents do not come within c. 650 km
of each other, plants of this hybrid had appeared only in gardens, mostly in
England, all as natural seedlings. But lately the hybrid has been made artificially
and the parentage confirmed. As stated above, practically all are sterile. But they
have the distinguishing feature of hardy hybrids, i.e. the young foliage is
discoloured and is yellow, orange or red. A few clones of good species may show
this feature too, which means that the converse is not entirely reliable as
evidence of hybridity. The white ‘Silberschmelze’ originated as a sport on the
pink 'Darley Dale’ in Germany in the 1930s. ‘Norman R. Webster' was a
seedling in his garden in Scotland in the 1950s. They are indistinguishable
(McClintock, 1971).

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D. McCLINTOCK

E. scoparia L.

The typical subspecies grows in the Mediterranean area and is a dull shrub
attaining perhaps 4 m.

In the Azores grows E. scoparia subsp. azorica (Hochstetter) D. A. Webb. This
is distinguished by its shorter darker corolla, making the stigma protrude more
prominently. But its look is characteristic with the foliage in decorative wavy
curls, reminiscent of Chamacyparis obtusa, and it “must have reched 30-35 ft”
(Guppy, 1917: 395).

In the Canaries is E. scoparia subsp. platycodon (Webb & Berthelot) Hansen &
Kunkel. This is recognizable by its stouter growth with thick spreading leaves,
and also by its larger size. It too can grow to 10.7 nr (35ft) with a good trunk.

Plants in Madeira come close to subsp. platycodon , but have recently been
separated as subsp. maderincola D. McClintock (1989c).

E. vagans L., E. manipuliflora Salisb., E. didyma Stokes & E. multiflora L.

These four species need considering together. It is clear from the lectotype of
E. vagans L. in LINN and other evidence, that this name refers to what is
nowadays called E. manipuliflora Salisbury. A case has been put (McClintock,
1989b) for its retention in the sense in which it has been universally used for 200
years or so. Until this is agreed, the plant of Western Europe must take the first
valid name given it, viz. E. didyma Stokes, which will be used here.

These species grow in distinct areas. Erica didyma is in N.W. Ireland
(McClintock & Rose, 1970; Nelson & Coker, 1974) S.W. England, W. France,
and N. Spain. In central southern France, the Balearics, Italy and the
N. Adriatic is E. multiflora L., distinct from the other three in its longer and
always parallel anthers. Erica vagans L. has generally been said to grow in S.E.
Italy (cf. Brullo et al ., 1986. Minnissala & Spampinato, 1986), the E. Adriatic
and in the Aegean and Turkey.

However, the Adriatic and Aegean plants of E. vagans are readily separable
many of the former very difficult to tell from E. didyma. As long ago as 1845 they
were distinguished as E. anthura Link. A visit to the area around and well to the
north of Dubrovnik in October 1988 confirmed the uniformity of the plants in
this area, which did not resemble those in the Aegean.

The characters of the Aegean plants, the type of E. manipuliflora , are white
stems to 3.7 m, short erect leaves and small flowers in a very much interrupted,
gappy, inflorescence, and they generally bloom later. In the Adriatric the stems
are brown, and not normally over 1.8 m (to 2.3 m rarely), the leaves longer and
often all spreading, or at least the lower ones are, and the well-scented
inflorescences dense, with negligible or no interruptions. Erica didyma can have an
even denser, more tapering, inflorescence and longer spreading leaves, but most
plants in Dalmatia look very like those of E. didyma,

Erica anthura has been placed by Nyman as a variety of E. vagans L. (by which
he clearly meant E. didyma) but it is distinctive enough to warrant specific status,
quite apart from the intrusive E. multiflora separating their areas.

These four species were well muddled by authors in the last century, so
contemporary records should be treated with caution. However, to recognize
four species seems to be the clearest way to group them.

A comment on E. didyma'. there is a curious Cornish variant, grown for nearly
80 years in gardens as ‘Viridiflora’. In this the llorets are replaced by pale green
feathery bracts. These have been proved to be the work of mites, occasionally the

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287

odd pink bell escaping their predation. It comes true from cuttings. Recently
analogous forms have been found, also in Cornwall (McClintock, 1 989a ; , and
the name f. viridula published for them.

E. ciliaris L.

The type is eglandular (McClintock, 1980b), although nearly all the cultivars
are glandular. This species has weak stems, but against a spruce tree a plant has
reached over 1.8 m on Soussons Downs in Devon (where the colony was
planted), and have been seen nearly as tall against a pine tree in Spain.

E. umbellata L.

Anandrous forms exist in most species (cf. Turpin, 1982). In E. umbellata. var.
anandra Lange, the precise deformity has been over-claimed for plants with
included anthers such as var. subcampanulata DC., which need further study.

E. sicula Gussone

This species was formerly included in the disregarded genus Pentapera. It was
named from Sicily, its only European station, where it was thought to have
become extinct, but has very recently been rediscovered. Elsewhere it can be
seen in S. Turkey, Cyprus, Lebanon and Libya. Two subspecies, libanotica
(Barbey) Yaltirik and cyrenaica Brullo & Furnari, have been published, but the
validity of their distinctions from subsp. sicula needs investigating (McClintock,
1980c; Meikle, 1985). This is a plant of lowland coastal limestone.

E. bocquetii Pe§men

Another plant of limestone but in the mountains, known only at 1750 m in the
E. Taurus. It is much smaller in all its parts, with leaves in threes, and anthers
without appendages. It has hardly been seen since it was named in 1968 (cf.
Browicz, 1983). This species was also included in Pentapera.

Hybrids between Erica species in different sections
E. x lazaroana Rivas Goday & Bellot

This was published in 1946 for a cross, said to be frequent in S.E. Spain,
between E. arborea and E. umbellata. No specimens have been seen. Nevertheless,
should such a hybrid appear this is the valid name. The authors also called their
plant E. x subcampanulata (DC.) Goday & Bellot, based on DeCandolle's variety
of umbellata.

E. watsonii Bentham (E. ciliaris L. x E. tetralix L.)

This had been long known in England and later in France, but the question to
be asked is why is it unknown in Spain (McClintock, 1983a: 37)? The type is
glandular (McClintock, 1980b). The inflorescence can differ in shape, but the
short appendages to the anthers are the sure key to its identity, plus its almost
complete sterility.

E. williamsii Druce (E. tetralix L. x E. vagans L.)

Still known only from the Lizard with only ten occurrences (cf. Turpin, 1983),
yet its parents grow near enough together elsewhere, e.g. in Spain. Is there some
sort of incompatibility at work?

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D. McCLINTOCK

The hybrid has recently been produced artificially, notably attempting to get
a white one. To this end two white cultivars were crossed and produced an
undoubted hybrid, but the flowers were pink. The explanation is to be seen in
the minutes of the Royal Horticultural Society Scientific Committee for
7 October 1986 and in Griffiths (1987).

Unsuccessful attempts were made in the past at the fiddling business of
crossing heathers. However, in the past ten years or so, Kurt Kramer, a
nurseryman of Edewecht — Siiddorf in Oldenburg, Germany (McClintock,
1985), independently followed by Dr John Griffiths (1985), a lecturer in colour
chemistry at Leeds University and David Wilson, a nurseryman of British
Columbia, have had successes. At this stage it is too early to do more than report
that this work is going on actively and making worthwhile progress. None of the
resultant hybrids, some new to science, including the first successful cross
between a European and S. African species, have yet been named.

Bruckenthalia

B. spiculifolia (Salisb.) Reichenb.

This is the counterpart on acid areas of the Balkans of the alkaline E. carnea
further west. Whether it should be returned to Erica, whence it started life, is
discussed by Oliver (1989).

REFERENCES

BEIJERINCK, W., 1940. Calluna. V erhandelingen der koninklijke nederlandsche akademie van wetens chap pen ( 2nd
section ), 138: 1-180.

BRANDHAM, P. & McCLINTOCK, D., 1983. The chromosome numbers of four hybrid heaths. Heather
Society Tear Book: 55.

BRICKELL, C. D. & McCLINTOCK, D., 1987. Proposal to conserve Erica carnea L. against E.herbacea L.
(Ericaceae). Taxon, 16: 479-481.

BRIEN, R. J., 1984. St Kilda Heathers. Heather Society Year Book: 4—7.

BRIQUET, J. I. & LITARDIERE, R. V. de, 1938 .'Prodrome de la Flore Corse, 3: 179.

BROWICZ, K., 1983. Chorology of Trees and Shrubs in South-West Asia and Adjacent Regions, 2: 9, 11—12, 42-43.
Warsaw.

BRULLO, S., MINNESSALA, P., SIGNORELLO, P. & SPAMPINATO, G., 1986. Studio fitisociologico
delle garighe ad Erica manipuliflora del Santo (Puglia meridionale). Archive botanico e biograjico italiano, 62-
(314): 201-14.

FOSS, P. J., DOYLE, G. J. & NELSON, E. C., 1987. The distribution of Erica erigena R. Ross^ in Ireland.
Watsonia, 16: 31 1-327.

FRAGA, VI. I., 1983. Numeros cromosomaticos de plantas occidentales 223-233. Anales del Jardin Botanico de
Madrid, 39: 533-539.

GREUTER, W., BURDET, H. M. & LONG, G., 1986. Med-Checklist, 3: 202.

GRIFFITHS, J., 1985. Hybridisation of the hardy Ericas. Heather Society Year Book: 17-34.

GRIFFITHS, J., 1987. Hybridisation of the hardy Ericas. Part 2 E. x williamsii, E. x watsonii and new hybrids
from E. manipuliflora. Heather Society Year Book: 42-50.

GUPPY, H. B., 1917. Plants, Seeds and Currents . . . in . . . Azores.

LAGUNA, S. M., 1890. Flora forestal Espahola, 11: 73. No. 201.

McCLINTOCK, D., 1971. Recent developments in the knowledge of European Ericas. Botanische Jahrbiicher,
90: 511.

McCEINTOCK, D., 1979. The chromosome numbers of heathers. The Plantsman, 1: 63-64.

McCLINTOCK, D., 1980a. Bell heathers with split corollas. The Plantsman, 2: 182-191.

McCLINTOCK, D., 1980b. The typification oil Erica ciliaris E., of if. tetralix E. and of their hybrid E. x watsonii
Bentham. Botanical Journal of the Linnean Society, 80: 207-21 1.

McCLINTOCK, D., 1980c. Erica sicula. Heather Society Year Book: 45-55.

McCLINTOCK, D., 1980d. The status of, and the correct name for, Erica ‘Stuartii'. Watsonia, 12: 249-252; 13:
59.

McCLINTOCK, D., 1 98 1 . The Bell heather in Madeira. Heather Society Year Book: 48-51.

THE HEATHERS OF EUROPE AND ADJACENT AREAS

289

McCLINTOCK, D., 1982. Erica tetralix met trosvormige bloeiwijzen. De levende Natur, 84 {5-6): 189.
McCLINTOCK, D., 1983a. Iter hispanicum ericaceum. Heather Society Tear Book: 33-40.

McCLINTOCK, D., 1983b. The Carna colony of Erica mackaiana, a new variety. Irish Naturalists’ Journal, 21:
85-86.

McCLINTOCK, D., 1985. Kurt Kramer’s new carneas. Heather Society Year Book: 13-14.

McCLINTOCK, D., 1986. Harmonising botanical and cultivar classification with special reference to hardy
heathers. Acta Horticulturae, 182: 277-283.

McCLINTOCK, D., 1989a. The “Viridiflora” variants of Cornish heath. Heather Society Tear Book: 52-54.
McCLINTOCK, D., 1989b. Proposal to conserve Erica vagans L. (Ericaceae) with a conserved type. Taxon, 38:
526-527.

McCLINTOCK, D., 1989c. The Erica scoparia in Madeira. Heather Society Tear Book: 32-36.

McCLINTOCK, D. & ROSE, F. R., 1970. Cornish heath in Ireland. Irish Naturalists’ Journal, 16: 387-390.
MACFARLANE, J. M., 1893. An examination of some Ericas. Transactions of the Botanical Society of Edinburgh,
19: 63-64.

MEIKLE, R. D., 1985. Flora of Cyprus, 2: 1060-1061. Kew: Bentham-Moxon Trust.

MINNISSALA, P. & SPAMPINATO, G., 1986. Sulla presenza in Italia di Erica manipuliflora Salisb. con
considerazioni sulla sua distribuzione ed ecologia. Giornale botanico Italiano, 120, Supp. 2: 86.

MUNSON, E. H., 1984. Heaths and heathers in N. America. Baileya, 22 (3): 101-133.

NELSON, E. C., 1989. Heathers in Ireland. Botanical Journal of the Linnean Society, 101: 269-277.

NELSON, E. C. & COKER, P. D., 1974. Ecology and status of Erica vagans in Co. Fermanagh, Ireland.
Botanical Journal of the Linnean Society, 69: 153-95.

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7: 25-33.

NELSON, E. C., McCLINTOCK, D. & SMALL, D., 1985. The natural habitat of Erica andevalensis in south¬
western Spain. Kew Magazine, 2: 324—330.

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TURPIN, P. G., 1982. A new and curious form of Erica vagans L. Watsonia, 14: 184—185.

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Botanical Journal of the Linnean Society (1989), 101: 291-299. With 15 figures

The different types and importance of British
heaths

LYNNE FARRELL

Nature Conservancy Council, Northminster House, Peterborough PEI 1UA

FARRELL, L., 1989. The different types and importance of British heaths. A synopsis of the
22 types of heathland recognized by the National Vegetation Classification is presented. Maps
showing their locations are given.

ADDITIONAL KEY WORDS: — Calluna - heathland — National Vegetation Classification
Nature Conservancy Council.

The National Vegetation Classification began in 1976. It is based at Lancaster
University and the main author of the publication is Dr John Rodwell (Rodwell,
1988). The aim of this Nature Conservancy Council project is to provide a
complete description and classification of the range of British plant communities,
omitting only those deliberately planted for agriculture or horticulture. This will
give us a working scheme enabling us to standardize our approach to habitat
and vegetation survey, mapping, monitoring and evaluation. It will also enable
a comparison to be made between British and European vegetation.

The heathland chapter was completed in June 1988. It distinguishes 22 types,
12 of these being essentially lowland heath types, usually found occurring on
land below 300 m. These 12 types are now described and their distributions in
Britain illustrated (Table 1 and Figs 113).

Britain is part of the Western Atlantic heathland zone (Fig. 14) distributed
along the Atlantic seaboard from Norway in the north, to Portugal in the south
and eastwards into Germany. Examples of three European heathland types are
found in Britain:

1. Anglo-Norman, NVC type H2 CallunajUlex minor.

2. Armorican, NVC types H3 Ulex minor \Agrostic curtisii and H4 Ulex galliij
Agrostis curtisii.

3. Ibero-Atlantic, NVC type H5 Erica vagans jSchoenus nigricans.

Because of our oceanic climate, wet and humid heathland types are better
developed and more extensive in Britain than in Europe.

In 1976 a report was produced for the Council of Europe on the heathlands of
Western Europe (Noirfaise & Vanesse, 1976). Although the facts and figures
have changed since then, and the extent of heathland has declined even lurther,
they indicate the decrease in the habitat that was widespread.

291

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292

L. FARRELL

Table 1. National Vegetation Classification for British heaths

NVC Type

Community

Distribution

Lowland

HI

CallunajFestuca ovina

S.E. & E. England (Breckland)

H2

Calluna fUlex minor

Weald, Sussex to Dorset

H3

Ulex minor- Agrostis curtisii

New Forest, W. to Dorset

H4

Ulex galliij Agrostis curtisii

S.W. England & S. Wales

H5

Erica vagans /Schoenus nigricans

The Lizard, Cornwall

H6

Erica vagans 1 Ulex europaeus

The Lizard, Cornwall

H7

Calluna/ Scilla verna

Coastal cliffs & islands

H8

Calluna/ Ulex gallii

S.W. England, Wales & N.
Midlands

H9

Calluna/ Deschampsia flexuosa

S. Pennines & Midlands

H10

Calluna/Erica cinerea

Low altitudes in Scotland

HI 1

Calluna/ Car ex arenaria

Coastal dunes & sandy

shingle

H12

Calluna/ Vaccinium myrtillus

Lower ‘moorland' of S.W. &

N. England & Scotland

Upland

H13

Calluna/ Cladonia arbuscula

H14

Calluna/ Rhacomitrium lanuginosum

H15

Calluna/ Juniperus communis nana

H16

Calluna/ Arctostaphylos uva-ursi

H17

Calluna/ Arctostaphylos alpinus

H18

Vaccinium myrtillus/ Deschampsia flexuosa

H19

V. myrtillus /Cladonia arbuscula

H20

V. myrtillus /Rhacomitrium lanuginosum

H21

Calluna/ V. myrtillus /Sphagnum

H22

V. myrtillus /Rub us chamaemorus

Wet Heath

M15

Scirpus cespitosa/ Erica tetralix

L'pland transition

M16

E. tetralix /Sphagnum compactun

Widespread

a. In Sweden and Denmark 60-70% was lost between 1860 and 1960. In 1976
13 575 ha remained chiefly in Danish reserves.

b. In N.W. France there were estimated 14 396 ha in 1979 (Nicholson, 1979).
This has now declined even further (personal observation).

c. In W. France 200 000 ha remained in 1955, but this represented only one-
third of the 1770 total.

d. The Belgo-Dutch Campine used to be covered by vast tracts of heath. It has
been reduced by 90% Most of the 1500 ha left is in nature reserves and military
camps.

e. Much of the heathland on the German plain has been lost.

f. Friesian coastal heaths have suffered greatly from tourism. In 1970 about
7000 ha remained.

g. Holland now has 42 000 ha left, where previously there were 800 000 ha.
This gives total of approx. 280 000 ha of heathland remaining in the rest of

Europe.

In Britain, the estimated extent in 1980 was 60 000 ha. Figures for England
and Wales are reasonably accurate and further survey work is underway in
Scotland at the present time. The acreages for different counties are shown in

BRITISH HEATH TYPES

293

Figures 1-4. Locations of heaths. Fig. 1. HI, Calluna vulgaris-Festuca ovina. Fig. 2. H2, Calluna vulgaris-
Ulex minor. Fig. 3. H3, Ulex minor- Agrostis curtisii. Fig. 4. Ulex gallii-Agrostis curtisii.

294

L. FARRELL

Figures 5-8. Locations of heaths. Fig. 5 H5, Erica vagans-Schoenus nigricans. Fig. 6. H6, Erica vagans-
Ulex europaeus. Fig. 7. H7, Calluna vulgaris-Scilla verna. Fig. 8. H8, Calluna vulgaris-Ulex gallii.

BRITISH HEATH TYPES

295

2 3 4 5 6

6

5

4

3

2

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Figures 9—11. Locations of heaths. Fig. 9. H9, Calluna vulgaris-Deschampsia flexuosa. Fig. 10. H10,
Calluna vulgaris-Erica cinerea. Fig. 11. Hll, Calluna vulgaris-Carex arenaria.

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Erica tetralix-Sphagnum compactum.

Figure 14. The main areas hatched in which lowland heaths occur in Western Europe from
Gimingham, 1972). Limit of Cfb Climate indicates oceanic type climate zone.

BRITISH HEATH TYPES

297

Table 2. Extent of lowland heathland in Britain in 1980s

Area Size (Taj

England

Bedfordshire

c. 20

Berkshire

515

Breckland

4529

Buckinghamshire

5

Cornwall & Scilly Isles (not Lizard)

2080

2080 Cumbria

520

Devon

c. 2000

Dorset

5670

Durham

c. 200

Essex

25

Hampshire

16 845

Humberside

13

Kent

55

Lincolnshire

c. 460

Lizard

2520

Merseyside

103

Norfolk (not Breckland)

729

North Yorkshire

c. 894

Nottinghamshire

c. 50

Oxfordshire

3

Somerset

c. 200

Suffolk Sandlings

1580

Surrey

3149

Sussex

1171

Westmidlands

Total

c. 45 02 1

Scotland

Aberdeen

675

Angus

448

Ardnamurchan

261

Argyll

200

Borders

1217

Caithness

486

Central

52

Dumfries

300

Fife

227

Inverness

29

Lothian

771

Orkney

200

Perth & Kinross

202

Ross & Cromarty

100

Shetland

200

Speyside

225

Sutherland

290

Western Isles

100

Total

6066

Wales

Gwynedd 1636

Pembrokeshire & Ceredigion c. 5000

c. 6635

57 222

Grand Total

298

L. FARRELL

Figure 15. The distribution of lowland heath in the British Isles. Accurate Scottish data still to be
collected.

Table 3. British heathland sites designated as biogenetic reserves

The Lizard NNR

Studland Heath NNR

Arne NNR and RSPB Reserve

Hartland Moor NNR

Morden Bog NNR

Cavenham Heath NNR

Thursley Common NNR

Sands of Forvie and Ythan Esturary NNR

Rhinog NNR

Muir of Dinnet NNR

Wan Fells SSSI

Lazonby Fells SSSI

BRITISH HEATH TYPES

299

Table 4. Eight additional heathland sites for possible inclusion in the future

St David’s Commons Wet & dry heath

Pebblebed Commons -Armorican

Lakenheath Warren- Anglo Norman

Bannau Preseli and Chomin Carnigli — Welsh/Irish

New Forest — Anglo Norman

Invernaver Scottish

North Hoy — Caledonian

Torrs Warren Dune heath

Table 2 and the distribution by Fig. 15. So Britain represents about 18% of the
total European resource.

At the third European Heathland Workshop held in Mols, Denmark, in
August 1988, it was agreed by all participants that an updated version of the
Council of Europe report should be produced. Representatives of each country
were nominated and the author agreed to co-ordinate the data being gathered
over the next two years. Each country was clearly of the opinion that a
European statement carried more weight when trying to protect the declining
heathland resources, than did a statement coming simply from one country.

In 1979 a biogenetic reserves group was set up to distinguish the most
important heaths in Europe and to provide them with further protection.
Twelve sites have been listed for Britain with recommendations for another eight
(Tables 3 & 4).

So why are our British heaths important?

1. They represent a large percentage of the remaining Europe resource.

2. The wet and humid heaths are particularly well represented because of our
geographical position in Europe.

3. Maritime heath is geographically widespread in Britain. As Britain has a
more extensive coastline than most European countries, so there are more
examples of maritime and coastal heath.

4. Mosaics of wet and dry heath as represented in Pembrokeshire are thought
to be unique.

REFERENCES

GIMINGHAM, C. H., 1972. The Ecology of Heathlands. London: Chapman & Hall.

NICHOLSON, P. B., 1979. A tour of the heathlands of N.W. France 27 Feb-11 Mar 1977. NCC S.W.
England regional report.

NOIRFALISIE, A. & VANESSE, R., 1976. Heathlands of Western Europe. Nature and Environment Series
No 2. Strasbourg: Council of Europe.

RODWELL, J., 1988. The National Vegetation Classification, Heaths, 1 & 2. L niversity of Lancaster, unpublished
report to the Nature Conservancy Council.

Botanical Journal of the Linnean Society (1989), 101: 301-306.

Management of heather for game and livestock

ROBERT MOSS

Institute of Terrestrial Ecology, Hill of Brathens, Banchory, Kincardineshire AB34B T,
Scotland

MOSS, R., 1989. Management of heather for game and livestock. Heather provides food and
cover for moorland herbivores. Interactions between soils, drainage, climate, muirburn and grazing
affect the species composition, structure and growth of moorland swards. Together, these aspects of a
sward determine which and how many herbivores it can support. Grazing and burning maintain
much heather ground which would otherwise revert to scrub or woodland. Heavy grazing by
ungulates can turn a heathery sward into a graminaceous one, so reducing numbers of grouse and
mountain hares. On good soils, invading graminoids are usually nutritious grasses and the carrying
capacity for ungulates can increase. On poor soils, grazing and frequent burning may lead to swards
dominated by poor quality grasses and sedges so that the carrying capacity for ungulates declines.
One way of reinstating heather dominance is to remove livestock; where there are no heather plants
left, other techniques may be necessary.

ADDITIONAL KEY WORDS: Grazing — grouse — mountain hares - muirburn - red deer
sheep - upland.

CONTENTS

Introduction .

Impact on heather of different animals

Muirburn .

Soils .

Sward height, structure and scale .
Grouse versus sheep ....

Acknowlegements .

References .

301

302

303

303

304

305
305
305

INTRODUCTION

Heather, Ling ( Calluna vulgaris (L.) Hull), is, in Britain, a major but declining
resource for upland game species, such as red grouse ( Lagopus lagopus scoticus (L.)
Latham), mountain hares (. Lepus timidus L.), black grouse ( Tetrao tetrix (L.)
Short), and red deer ( Cervus elaphus L.), and also for hill sheep and cattle. Most
heather occurs as dominant or co-dominant in open heath, bog, moorland and
summit vegetation. It provides both food and cover but has been little valued by
farmers because of its relatively poor nutritive value (Grant et al., 1982). By both
design and accident, much management of domestic stock has tended to suppress
or eliminate heather and so reduce the range and abundance of heath-dependent
small game species such as red grouse, black grouse and mountain hares
(Hewson, 1956; Miller, Jenkins & Watson, 1966; Yalden, 1971, 1979, 1986;
Hope Jones, 1987; Parr & Watson, 1988).

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© 1989 The Linnean Society of London

302

R. MOSS

There have been four main management tools. 1. Fertilizing and reseeding
heather ground with grass, often with ploughing. 2. Grazing. 3. Burning. 4.
Draining. The response of heather to grazing and burning varies greatly with
their intensity and pattern, and also depends upon soil and climate, the species
composition and structure of the sward, and the animals doing the grazing.
Grazing and burning of moorland prevent regeneration of natural scrub and
forest, and can result in heather being replaced by grassy vegetation (Grant &
Maxwell, 1988). When combined with trampling and poaching, these practices
can also led to erosion of soils, especially peats. The productivity, species
composition and structure of heathery swards are determined partly by the
domestic and wild animals using them. In turn, the type of sward affects the
species, density and productivity of the animals present.

The possible interactions between soils, plants, grazing animals and climate
are many, and poorly understood. Here I shall briefly outline some broad
working principles.

IMPACT ON HEATHER OF DIFFERENT ANIMALS

Red grouse eat largely heather all year (Eastman & Jenkins, 1970), though
they can benefit from supplements of other foods. Even at high densities, red
grouse eat probably less than 10% of a heather sward’s annual production of
green shoots (Savory, 1978). Young heather can withstand removal of 40% of its
annual production of green shoots without affecting its productive capacity the
following year (Grant et al., 1978). The only gross effect that grouse are likely to
have on a heather sward is to delay very slightly its mean rate of increase in
height. Black grouse, although about twice the weight of red grouse (1200 vs.
600 g for average adults), eat a smaller proportion of heather (Johnstone, 1969)
and do not reach the same high densities. Their impact, therefore, is likely to be
negligible.

Mountain hares (2. 5-3. 0 kg) also eat much hether (Hewson, 1962). Of the
small game species, hares have the biggest impact on heather but even when
abundant they usually only slow its growth and alter its form (Welch & Scott,
1984; Moss & Hewson, 1985).

Ungulates, unlike red grouse and mountain hares, seem to need a fairly high
proportion of graminoid foods in their diet and do not thrive on heather alone
(Grant et al., 1982; Mitchell, Staines & Welch, 1977). Hence their impact on
heather depends partly upon the availability of palatable grasses and other
graminoids. Close by grassy swards, grazing and trampling by red deer, sheep
and cattle can lead to reduction or elimination of heather (Welch, 1984). On
well-drained moorland soils, heather is often replaced by grasses; these can
attract more grazers which eat more heather and cause further expansion of
grass. Many of the once-heathery hillsides of north Wales, for example, are now
grassy sheep walks for this reason; the heather-dependent red grouse is far
scarcer there than it was and there may be only a few hundred black grouse left
in Wales (Hope Jones, 1987).

In the Scottish Highlands, numbers of red deer have increased markedly in
recent decades (Red Deer Commission, 1987). During this increase, annual
variations in deer performance seem to have been density-dependent (Clutton-

HEATHER MANAGEMENT

303

Brock, Albon & Guinness, 1987) and related to food supplies and snow cover
(Albon & Clutton-Brock, 1988). If food is limiting, as this suggests, numbers of
red deer have presumably been approaching the carrying capacity of the
Scottish Highlands and one might have expected catastrophic mortality in
severe winters. Instead of such mortality, however, the extent of grassy swards
has increased in some glens (Watson, 1989). Heavy grazing by red deer, perhaps
together with sheep, may have increased the carrying capacity of Scottish hills
for red deer by making more grass available. If so, deer as well as sheep may
have contributed to a reduced carrying capacity for grouse.

MUIRBURN

The size and frequency of fires in a burning regime depend upon their
purpose. Red grouse are territorial, needing relatively short heather for food and
tall heather for cover (Watson et al., 1976). Burning moorland heather on a 10
20 year rotation in small patches or narrow (20-35 m) strips increases the
amount of edge between tall and short heather. This allows small territories and
consequently high densities. Since grouse prefer to feed within a few metres of
cover (Savory, 1974), large expanses of very short heather support few grouse. At
the other extreme, large areas of tall, old heather usually support lower densities
of grouse than patchily-burned areas but higher densities of grouse than large
areas of very short heather.

Black grouse are usually associated with taller heather than red grouse but
how muirburn affects them is not well understood. Mountain hares are usually
associated with short heather and occur widely on the dwarf shrub summit
heaths of Scotland, which are not burned but kept short by wind and weather.
They also occupy lower ground, particularly where some heather is kept short by
muirburn and grazing.

Sheep management usually involves bigger and more frequent fires than
grouse management. Young heather, newly regenerating after a fire, is more
nutritious than old heather; fire also burns tussocks and mats of dead grass,
making room for new, accessible leaves which sheep can graze.

Management of deer forests is generally less intensive than for either red
grouse or sheep. Fires of large or moderate size are typically burned, but deer
forests generally contain more old heather than sheep walks.

SOILS

The effects of grazing and burning on an initially heathery sward differ
considerably with soil and bioclimatic zone. Well-drained, lime-rich soils can
attract heavy grazing by sheep and deer, associated with development of herb-
rich, grassy swards. Grass swards can develop on many well-drained hill soils,
but the more acid soils usually support more of the less palatable grasses. On
well-drained acid soils, typical of eastern Scottish moors, heather can tolerate
moderate grazing by ungulates without being displaced by grass. In these
circumstances, heather regenerates freely following fire and this is ideal for
grouse management.

304

R. MOSS

If heather on the more basic moorland soils is not overgrazed, it grows faster,
is nutritionally richer and supports higher average densities of grouse than on
acid soils (Moss, 1969). Heather can also be enriched by artificial fertilizing, but
other grazing animals can eat the fertilized heather, so annihilating potential
benefit to grouse (Watson et al., 1977). The growth and nutritive value of
heather are generally poorest on deep blanket peats, where the main input of
nutrients is from the atmosphere (Moore, Dowding & Healy, 1975 ).

Where drainage is poor, heather growth and nutritive value can sometimes be
improved by draining (Phillips & Moss, 1977). Surface drains may have little
effect since lateral percolation of water in peaty soils is often slow. Where
drainage is impeded by iron pans, shattering them with a deep subsoiling tine
can be effective.

Sward management on wet acid soils and deep peat often involves large,
frequent fires aimed at producing new growth for sheep. How grazing and
burning interact under such circumstances is not well understood. Some stages
which occur, however, are clear. First, heather tends to be replaced by
graminoids. Second, more palatable graminoids are grazed preferentially and on
poor soils can be replaced by less palatable ones. At the same time, rapidly
colonizing graminoids tend to be replaced by slower colonizers. These two
processes often act in the same direction since faster colonizing species are
generally more palatable. Third, trampling, especially in the hre-induced
absence of stabilizing root, mat and tussock, can accelerate erosion, particularly
of peat. Fourth, the erosion of peat down to mineral soil can lead eventually to
'islands’ of peat remnants separated by erosion channels (D. Henderson,
personal communication). This makes further burning impracticable and may in
time lead to the establishment of patches increasingly dominated by heather and
protected from burning by erosion channels.

SWARD HEIGHT, STRUCTURE AND SCALE

Small-scale patchworks of tall and short heather benefit red grouse (above).
Tall heather can also shelter red deer (Mitchell et al., 1977) and sheep. Lance &
Triggs (1974) showed that lambs grew better in a patchwork than on large-scale,
frequent fires typical of much hill sheep management. Small-scale burning,
however, is labour intensive.

The relationship between the height and age of heather varies with local
conditions: heather of a given age is taller on low, fertile, sheltered and lightly
grazed areas. For feeding, mountain hares (Hewson, 1974) and sheep (Milne,
Bagley & Grant, 1979) prefer short, young, pioneer heather; red grouse prefer
slightly older and taller heather up to 30 cm (Moss, Miller & Allen, 1972) whilst
limited evidence suggests that red deer prefer heather over 25 cm in height
(Hewson, 1976).

A main cause of long term declines in red grouse has been the poor
management of heather swards by too-frequent burning, underburning and
overgrazing, and associated loss of accessible food or cover (Watson et al., 1976).
Small-scale patchworks of long and short heather, experimentally created on
poorly managed areas of low grouse density in Mull (Watson, Moss & Parr,
1987) and Mayo (Watson & O'Hare, 1979), were accompanied by increases in
grouse stocks. A puzzle is that these increased densities were still lower than those

HEATHER MANAGEMENT

305

obtained with similar management on traditional grouse moors. This suggests an
effect of scale, such that an area of well-managed heather of a hundred hectares
or so, set in a large area of poorly managed ground, supports lower densities than
much bigger tracts of well-managed heather.

This may help to understand the dramatic decline of red grouse in west
Scotland relative to the east. If one starts with a large area of good-quality
habitat and allows a small proportion of it to deteriorate, grouse numbers may
initially fall in parallel with the proportion of poor habitat. At some point,
however, the ratio of poor to good habitat may reach a critical point. The good
habitat may be so fragmented that it comprises islands of good habitat in a sea of
poor. The effect of scale, above, may then cause an accelerated reduction in
grouse stocks disproportionate to the amount of poor habitat.

GROUSE VERSUS SHEEP

Heavy grazing by ungulates, especially when combined with overburning, can
displace heather, grouse and hares. If a landowner wants both sheep and grouse,
for example, he must manage the structure of his sward. This should include a
reasonable mixture of long and short heather. Rotational fencing may be a
practical way of maintaining some long heather in the face of heavy grazing,
particularly where heather regenerates poorly. However, many British uplands
have passed the point where heather can be restored by exclusion of livestock.
There are too few heather plants left. Where viable heather seeds remain in the
soil, regeneration by tillage may be possible, perhaps with the help of selective
herbicides to reduce competition from grasses (Reconciliation Project, 1988).

With more food from the lowlands there is less justification for keeping
subsidized sheep in the uplands. There is also increasing demand from newly
affluent Britons for game shooting. It may be time for more research into
improved methods of heather management.

ACKNOWLEDGEMENTS

I thank D. Welch, A. Watson and B. W. Staines for constructive discussions
and criticism.

REFERENCES

ALBON, S. D. & GLUTTON-BROCK, T. H., 1988. Climate and the population dynamics of red deer in
Scotland. In M. B. Usher and D. B. A. Thompson (Eds), Ecological Change in the Uplands. Special Publication
Number 7 of the British Ecological Society : 93-107. Oxford: Blackwell Scientific Publications.

CLUTTON-BROCK, T. H., ALBON, A. D. & GUINNESS, F. E., 1987. Interactions between population
density and maternal characteristics affecting fecundity and juvenile survival in red deer. Journal of Animal
Ecology, 56: 857-871.

EASTMAN, D. S. & JENKINS, D., 1970. Comparative food habits of red grouse in north-east Scotland, using
faecal analysis. Journal of Wildlife Management, 34: 612-620.

GRANT, S. A. & MAXWELL, T. J., 1988. Hill vegetation and grazing by domesticated herbivores: the
biology and definition of management systems. In M. B. Usher & D. B. A. Thompson (Eds), Ecological
Change in the Uplands. Special Publication Number 7 of the British Ecological Society: 201-214. Oxford: Blackwell
Scientific Publications.

GRANT, S. A., BARTHRAM, G. T., LAMB, W. I. C. & MILNE, J. A., 1978. Effects of season and level of
grazing on the utilization of heather by sheep. 1. Responses of the sward. Journal of the British Grassland
Society, 33: 289-300.

306

R. MOSS

GRANT, S. A., MILNE, J. A., BARTHRAM, G. T. & SOUTER, W. G., 1982. Effects of season and level of
grazing on the utilization of heather by sheep. 3. Longer-term responses and sward recovery. Grass and
Forage Science, 37: 31 1-320.

HEWSON, R., 1956. The mountain hare in England and Wales. Naturalist, 81: 107-109.

HEWSON, R., 1962. Food and feeding habits of the mountain hare Lepus timidus scoticus, Hilzheimer.

Proceedings of the Zoological Society, London, 139: 515-526.

HEWSON, R., 1976. Grazing by mountain hares Lepus timidus L., red deer Cervus elaphus L. and red grouse
Lagopus l. scoticus on heather moorland in north-east Scotland. Journal of Applied Ecology, 13: 657-666.
HOPE JONES, P., 1987. Black grouse habitat and food in North Wales, 1986. Lmpublished report to the Forestry
Commission by the Royal Society for the Protection of Birds, Sandy, Bedfordshire.

JOHNSTONE, G. W., 1969. Ecology, dispersion and arena behaviour of Black Grouse Lyrurus tetrix ( L.) in Glen Dye,
NE Scotland. Unpublished Ph.D. thesis of the Lhiiversity of Aberdeen.

LANCE, A. & TRIGGS, R., 1974. Developing hill bogland to benefit both grouse and sheep. Farm and Food
Research, 5: 135-136.

MILLER, G. R., JENKINS, D. & WATSON, A., 1966. Heather performance and red grouse populations. I.

Visual estimates of heather performance. Journal of Applied Ecology, 3: 313-326.

MILNE, J. A.,. BAGLEY, L. & GRANT, S. A., 1979. Effects of season and level of grazing on the utilization
of heather by sheep. 2. Diet selection and intake. Grass and Forage Science, 34: 45-53.

MITCHELL, B., STAINES, B. W. & WELSH, D., 1977. Ecology of Red Deer. Cambridge: Institute of
Terrestrial Ecology.

MOORE, J. J., DOWDING, P. & HEALY, B., 1975. Glenamoy, Ireland. In T. Rosswall & O. W. Heal
(Eds), Structure and Function of Tundra Ecosystems, Ecological Bulletin (Stockholm) , 20: 321-343.

MOSS, R., 1969. A comparison of red grouse ( Lagopus l. scoticus) stocks with the production and nutritive value
of heather ( Calluna vulgaris ). Journal of Animal Ecology, 38: 103-122.

MOSS, R. & HEWSON, R., 1985. Effect on heather of heavy grazing by mountain hares. Holarctic Ecology, 8:
280-284.

MOSS, R., MILLER, G. R. & ALLEN, S. E., 1972. Selection of heather by captive red grouse in relation to
the age of the plant. Journal of Applied Ecology , 9: 771-781.

PARR, R. & WATSON, A., 1988. Habitat preference of Black Grouse on moorland-dominated ground in
north-east Scotland. Ardea, 76: 175-180.

PHILLIPS, J. & MOSS, R., 1977. Effects of subsoil draining on heather moors in Scotland. Journal of Range
Management, 30: 27-29.

RECONCILIATION PROJECT, 1988. Fourth Annual Report. Eccles House, Thornhill, Dumfriesshire.

RED DEER COMMISSION, 1987. Annual Report For 1986. Edinburgh: Her Majesty’s Stationery Office.
SAVORY, C. J., 1974. The feeding ecology of red grouse in north-east Scotland. Lmpublished Ph.D. thesis of the
University of Aberdeen.

SAVORY, C. J., 1978. Food consumption of red grouse in relation to the age and productivity of heather.
Journal of Animal Ecology, 47: 269-282.

WATSON, A., 1989. Recent influences on grouse habitat from increases in red deer. The Joseph Nickerson
Reconciliation Project, Fifth Annual Report: 45-46.

WATSON, A. & O’HARE, P. J., 1979. Red grouse populations on experimentally treated and untreated Irish
bogs. Journal of Applied Ecology, 16: 433-452.

WATSON, A., MOSS, R. & PARR, R., 1987. Grouse increase on Mull. Landowning in Scotland, 207: 6.
WATSON, A., MOSS, R., PHILLIPS, J. & PARR, R., 1977. The effect of fertilizers on red grouse stocks. In
P. Pesson & M. G. Birkan (Eds), Ecologie du Petit Gibier et Amenagement des Chasses: 193—212. Paris:
Gauthier-Villars.

WATSON , A., MILLER, G. R., JENKINS, D., JACKSON, D. & PHILLIPS, J., 1976. Grouse Management.
Fordingbridge: Game Conservancy.

WELCH, D., 1984. Studies in the grazing of heather moorland in north-east Scotland. II. Response of heather.
Journal of Applied Ecology, 21: 197-207.

WELCH, D. & SCOTT, D., 1984. Further observations on a Callunetum intensively grazed by mountain
hares ( Lepus timidus L.). Transactions of the Botanical Society of Edinburgh, 44: 323-333.

YALDEN, D. W., 1971. The mountain hare ( Lepus timidus L.) in the Peak District. Naturalist, 96: 81-92.
YALDEN, D. W., 1979. An estimate of the number of red grouse in the Peak District. Naturalist, 104: 5-8.
YALDEN, D. W., 1986. The further decline of black grouse in the Peak District 1975-1985. Naturalist, 111:
3-8.

Botanical Journal of the Linnean Society (1989), 101: 307-312.

The invertebrates of heather and heathland

N. R. WEBB

Furzebrook Research Station, Institute of Terrestrial Ecology, Wareham, Dorset
BH20 5 AS

WEBB, N. R., 1989. The invertebrates of heather and heathland. The southern heathlands of
Great Britain have long been renowned amongst entomologists. The invertebrates fall into two
groups: species which feed on heathland plants — about 40 in the case of Calluna — and a second
group which depends on the particular physical conditions provided by heathland, such as hot dry
sandy areas or the micro-topography of Sphagnum bogs. The ecology of representative examples will
be described, and the effects of fragmentation and isolation of the heathlands on the distribution and
abundance of invertebrates discussed.

ADDITIONAL KEY WORDS: — Calluna - Erica - fauna - insects.

CONTENTS

Introduction .
Herbivores of Calluna .
The fauna of Calluna
Heathland invertebrates
References

307

308
308

310

311

INTRODUCTION

Most of the north-west European heathlands are anthropogenic. They came
into existence following forest clearances which commenced three to four
thousand years ago, and have been perpetuated by the use of the land
(Gimingham, 1972; Webb, 1986). In evolutionary terms this is a relatively short
period for a well-defined community to develop.

Changes in the structure and composition of the vegetation through succession
need to be controlled by management. Invertebrates generally respond rapidly
to small scale changes in their environments, and it is interesting to speculate to
what extent the management of the vegetation by man has been a selective force
modifying the life cycles and dispersal abilities of many insects.

Invertebrates have complex life cycles. The habitat of each stage — egg, larva,
pupa and adult — is different and these habitats must occur correctly in time and
space for the life cycle to be completed.

The invertebrate fauna will be reviewed in two sections: first, the fauna which
feeds on heather ( Calluna vulgaris) and second, that which occurs more generally
on heathland. Associated with the fauna of Calluna is that dependent on species
of Erica, this is of similar composition but less well known. The presence of

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subordinate plant species in the vegetation will also affect the composition of the
general fauna. Much of the general fauna of heathland depends on the physical
conditions, particularly those accompanying changes in vegetation structure
throughout the growth phases of heather (Watt, 1955). Other species require
conditions such as hot, dry, sand or acid wetlands.

HERBIVORES OF CALLUNA

Calluna is an evergreen sclerophyllous plant well adapted to xeric and
nutrient poor conditions. The leaves have a thick cuticle, thick-walled cells, and
high content of lignin, tannins, phenolic compounds, resins and essential oils.
These features may be a response to nutrient-poor conditions, especially to a
deficiency of phosphorus (Specht, 1979) and their presence increases the
flammability of the vegetation with important consequences for the community
through management by burning.

Theories of plant-herbivore interaction suggest that, in many plants, the
production of secondary metabolites has been evolved as a defensive response to
invertebrate herbivore attack. Recently, it has been suggested that the
accumulation of carbon-based secondary compounds may be a function of the
carbon-nutrient balance of the plant and not primarily a response to herbivore
attack. If nutrients are not limiting, carbon is used for growth, but under
conditions of nutrient stress there is an accumulation of carbon-based secondary
compounds. (Tuomi et al., 1988; Edwards, in press.) Calluna may be a plant in
which secondary compounds have been produced as a result of environmental
stress and not as a response to herbivore attack.

About forty species of insect depend on Calluna for food and this is
approximately the number to be expected from the architecture and
geographical distribution of Calluna (Lawton & Schroder, 1977). When
compared with plants which contain higher levels of nitrogen, the fauna of
Calluna occurs at low densities. It contains species which tend to be sedentary,
often remaining on the same plant, and pass through one generation a season. In
some cases, two seasons are required for the completion of the life cycle (McNeill
& Prestige, 1982).

Studies on the herbivore fauna of Calluna (McNeill & Brown, personal
communication) have shown that the density of herbivores depends seasonally
on the levels of nitrogen in the shoots and that the number of herbivore species
present during the heathland succession is related to spatial and architectural
diversity of the plants and the levels of phenolic compounds.

THE FAUNA OF CALLUNA

The flowers of Calluna contain good numbers of thrips (Thysanoptera), the
commonest being Ceratothrips ericae. These insects, which feed on pollen, lay their
eggs in the nectaries at the base of the flowers. Females moving from plant to
plant to oviposit act as important pollinators (Haegerup, 1950).

There are about six species of Hemiptera: Heteroptera and five species of
Homoptera associated with heather (Table 1). These have sucking mouthparts
and mostly feed on the cell sap but some, such as Ulopa reticulata, tap into the
phloem and others such as members of the Lygaeidae, feed on seeds. The

HEATHLAND AND HEATHER INVERTEBRATES

309

Heather Psyllid ( Strophingia ericae ) has been shown to have a lowland race which
completes its life cycle in one year and an upland race requiring two years
(Parkinson & Whittaker, 1975).

In contrast, the Lepidoptera have biting mouthparts and eat the shoots or
foliage (Table 1). Members of the Eupitheciidae eat the flowers. Some of the
best-known and attractive heathland insects occur amongst the Lepidoptera
such as Saturnia pavonia and Macrothylacia rubi. Lycophotia porphyrea and Anarla
myrtilli are two very similar-looking noctuid moths which feed on heather, and
which may be very abundant. The caterpillars are less easily found, especially
those of L. porphyrea which feed at night. There are about 17 species of moth
which feed on heather of which about eight are monophagous.

Beetles (Coleoptera) associated with heather eat either foliage or in the case of
the larvae of some weevils, the roots. The Heather Beetle ( Lochmaea suturalis) is
the most familiar species. Both the adult beetles and the larvae eat heather
foliage. The Heather Beetle, which is about 6 mm long, occurs widely on all
heathlands, although its abundance varies locally. In the lowlands large
outbreaks occur from time to time (approximately ten-yearly), but on the
northern grouse moors outbreaks are more frequent and it can be a pest.
Severely-attacked plants show a characteristic reddening (‘frosted heather’) of
the foliage and on close inspection the damage caused by the beetles is clear.

The adult beetles swarm in the spring (March/April) when they also mate.
The eggs are laid on the heather plants or on the litter surface and hatch in 3-4
weeks. The three larval stages feed on the Calluna plants from June until early

Table 1. A list of the insects more commonly found feeding
on heather ( Calluna vulgaris). A fuller list appears in Webb
(1986). Species marked * do not feed exclusively on Calluna

Thysanoptera
Ceratothrips ericae

Hemiptera: Heteroptera
Kleidocerys truncatulus
Stygnocoris pedestris*
Macrodema micropterum
Ischnocoris angustulus
Scolopostethus decoratus
Orthotylus ericetorum

Lepidoptera
Coleophora juncicolella
Coleophora pyrrhulipennella
Aristotelia ericinella
Lita virgella
Scythris empetrella
Acleris hyemana
Macrothylacia rubi*

Saturnia pavonia*

Eupithecia goossensiata
Eupithecia nanata
Gymnoscelis rufifasciata*
Pachycnemia hippocastanaria
Paradiarsia glareosa*
Lycophotia porphyrea
Xestia castanea
Xestia agathina
Anarta myrtilli

Hemiptera: Homoptera
Ulopa reticulata
Scleroracus corniculus
Scleroracus plutonius
Cjgina rubrovittata
Strophingia ericae

Coleoptera
Lochmaea suturalis
Strophosomus sus
Micrelus ericae*

310

N. R. WEBB

August when they pupate in the litter. The immature beetles emerge in
September and continue to feed on the Calluna plants until they start to
hibernate in the litter (Cameron, McHardy & Bennett, 1944).

The dynamics of heather beetle populations are poorly understood. Two
predators, the pentatomid bug Rhacognathus punctatus and the ladybird Coccinella
hieroglyphica have been suggested as population regulators but these are
uncommon on heathland. The eulophid wasp Aescodes mento which parasitizes the
larvae is sufficiently abundant but its role as a population regulator has yet to be
investigated. The parasitoid was first recognized in the north of Britain
(Golightly, 1962); levels of parasitism up to 55% have been reported (Waloff,
1987).

In recent years in the Netherlands, defoliation and death of Calluna plants
through beetle outbreaks have become more frequent and have led to the
replacement of dwarf shrub communities by grasslands dominated by
Deschampsia flexuosa or Molinia caerulea (Brunsting, 1982). The increases in
fecundity, growth rates and survival of the beetles leading to increases in
population have been attributed to increases in deposition of atmospheric
nitrogen, particularly ammonia produced by intensive farming operations.

HEATHLAND INVERTEBRATES

Although these invertebrates are considered to be heathland species, they do
not depend directly on heather as a food plant. Many can be found in other
types of vegetation. They depend on the physical conditions on heaths and the
microclimate within dwarf vegetation. This varies with the growth phases of the
heather (Table 2), leading to changes in the habitats of many invertebrates
within a single heath. The habitat requirements of the Silver-studded Blue
(. Plebejus argus ) and the Grayling ( Hipparchia semele) typify many of these features.

Plebejus argus occurs both on heathland and on calcareous grasslands. Few
grassland colonies remain in Britain and those on heathland have decreased

Table 2. Characteristics of the heathland microclimate (after Barclay-Estrup, 1971)

Pioneer

Building

Mature

Degenerate

Age (years)

3-10

7-13

12-28

16-29

Percentage of
over-storey

10

85

75

35

Illumination at

High

Reduced

Increased to 20% of

Lp to 75% of

ground level

to 2% of ambient

ambient

ambient

Surface max.

Highest

Intermediate

Lowest

Second highest

Surface min.

Intermediate

Second highest

Highest

Lowest

Soil max.

High

Lowest

Intermediate

Highest

Soil min.

Low

Lowest

Highest

Intermediate

Saturation deficit

High

Low

Low

Increasing (high
on warm clays)

Air movement

Maximal

Negligible

Restricted

Much greater

Throughfall

At a maximum

At a minimum

Still at a low level

Much greater,
approaching that
of pioneer phase

HEATHLAND AND HEATHER INVERTEBRATES

311

considerably. The strongholds are now the heaths of Dorset and the New Forest
(Heath, Pollard & Thomas, 1984). Its food plants are Lotus corniculatus ,
Helianthemum nummularium, Ulex spp, Calluna vulgaris, Erica cinerea and E. tetralix.
There is a very close association with ants: larvae are tended by Lasius alienus or
L. niger, and the pupa is taken into the ants’ nest. This butterfly occurs in discrete
colonies on heathland and is one of the most sedentary of British butterflies,
adults seldom flying more than five metres from the point where they emerge. Its
habitat is fairly short open heath vegetation similar to the building phase or
alternatively, humid heath where the presence of Erica tetralix in the vegetation
provides a similar open structure. The openness of the vegetation and the levels
of insolation determine the distribution of the ants, with which the Silver-studed
Blue is associated.

Hipparchia semele is a grass-feeding species and occurs over a wide range of soil
and vegetation types. Although this species is common on many of the southern
heaths, it is not confined to heathland. It prefers sheltered, extremely well-
drained sites with sparse vegetation (Heath et al., 1984); a requirement that can
be met on grasslands as well as heathlands. However, it has declined
considerably at many inland localities and is now rare except on the southern
heaths and on the coasts. In this butterfly, cryptic colouration is well developed
and at rest the butterfly is difficult to discern against bare sandy soil.

A variety of other notable lepidoptera are associated with the southern
heathlands and include Cleora cinctaria, Chlorissa viridata and the Pachythelia
villosella with its remarkable life cycle (Heath, 1946).

Bare sandy areas on heathland are important for a variety of insects such as
ground beetles, tiger beetles and fossorial wasps. In recent years heath
management has tended to favour a uniform cover of dwarf shrubs with few of
the bare sandy areas.

The wetlands of the southern heathlands are important habitats for
dragonflies (Odonata). The majority of British species are associated with acid
waters and the wide variety from small streams, pools and seepages on Sphagnum
bogs, provide a wide range of habitats.

Studies on the invertebrate community of the Dorset heathlands (Webb, 1989;
Webb & Hopkins, 1984; Hopkins & Webb, 1984) have investigated the effects of
fragmentation, isolation and surrounding vegetation types. The observed
responses of the invertebrates have suggested ways in which heathland can be
assessed and how the remaining heathland patches should be viewed within a
landscape matrix in which there is interaction between the fauna of heathland
patches and their surrounding vegetation.

REFERENCES

BARCLAY-ESTRUP, P., 1971. The description and interpretation of cyclical processes in a heath community.

III. Microclimate in relation to the Calluna cycle. Journal of Ecology, 59: 143-166.

BRUNSTING, A. M. H., 1982. The influence of the dynamics of a population of herbivorous beetles on the
vegetational patterns in a heathland system. Proceedings 5th International Symposium Insect-Plant Relationships,
Wageningen, 1982: 215-223. Wageningen: Pudoc.

CAMERON, A. E., McHARDY, J. W. & BENNETT, A. H., 1944. The Heather Beetle (Lochmaea suturalis); its
Biology and Control. Petworth: British Field Sports Society.

EDWARDS, P. J., in press. Insect herbivory and plant defence. British Ecological Society Jubilee Symposium.
GIMINGHAM, C. H., 1972. Ecology of Heathlands. London: Chapman & Hall.

GOLIGHTLY, W. H., 1962. Biological control of Lochmaea suturalis (Thompson! Col: Chrysomelidae) .
Entomologists’ Monthly Magazine, 98: 196.

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N. R. WEBB

HEATH, I., 1946. The life history of Pachythelia villosella Ochs. (Lep., Psychidae). Entomologists’ Monthly
Magazine, 82: 59-63.

HEATH, J., POLLARD, E. & THOMAS, J. A., 1984. Atlas of British Butterflies. London: Viking Press.

HAEGERUP, O., 1950. Thrips pollination in Calluna. Biologiske Meddelelser, 18: 1-16.

HOPKINS, P. J. & WEBB, N., R., 1984. The composition of the beetle and spider faunas on fragmented
Calluna heathland. Journal of Applied Ecology, 21: 935-946.

LAWTON, J. H. & SCHRODER, D., 1977. Effects of plant type size of geographical range and taxonomic
isolation on the insect species associated with British plants. Nature, London, 265: 137-140.

McNEILL, S. & PRESTIGE, R. A., 1982. Plant nutritional strategies and herbivore community dynamics. In
J. H. Visser & A. K. Minks (Eds), Proceedings 5th International Symposium, Insect-plant Relationships, Wageningen
1982: 225-235. Wageningen: Pudoc.

PARKINSON, J. D. & WHITTAKER, J. B., 1975. A study of two physiological races of the heather psyllid
Strophingia ericae (Curtis). Biological Journal of the Linnean Society, 7; 73-81.

SPECHT, R., 1979. Ecosystems of the World , 9A. Amsterdam: Elsevier.

TUOMI, J., NIEMALA, P., CHAPIN, F. S., BRYANT, J. P. & SIREN, S., 1988. Defensive responses of trees
in relation to their carbon nitrogen balance. In W. J. Mattson, J. Levieux & C. Bernard-Dagan (Eds),
Mechanisms of Woody Plant Defenses against Insects: 57-72: Berlin: Springer.

WALOFF, N., 1987. Observations on the heather beetle Lochmaea suturalis (Thompson) (Coleoptera,
Chrysomelidae) and its parasitoides. Journal of Natural History, 21: 545-556.

WATT, A. S., 1955. Bracken versus heather, a study in plant sociology. Journal of Ecology, 43: 490-506.

WEBB, N. R., 1986. Heathlands. London: Collins.

WEBB, N. R., 1989. Studies on the invertebrate fauna of fragmented heathland in Dorset and the implications
for conservation. Biological Conservation, 47: 153-165.

WEBB, N. R. & HOPKINS, P. J., 1984. Invertebrate diversity of fragmented Calluna heathland. Journal of
Applied Ecology, 21: 921-933.

Botanical Journal of the Linnean Society (1989), 101: 313-318. With 1 figure

An assessment of the importance of heathlands
as habitats for reptiles

IAN F. SPELLERBERG

Department of Biology, University of Southampton, Southampton S09 5NH

SPELLERBERG, L F., 1989. An assessment of the importance of heathlands as habitats

for reptiles. Britain has a species-poor reptile fauna of six species. Although they occur in
association with various types of plant communities, most species seem to be associated with
heathlands. The lizard Lacerta agilis is particularly associated with heathlands but data presented
here suggests that the vegetation structure of typical, undisturbed, lowland heathlands is less suitable
for this species than disturbed heathland with more structural diversity.

ADDITIONAL KEY WORDS: — Vegetation structure - Lacerta agilis.

CONTENTS

Introduction .

Endangered reptile species in Britain
Material and methods ....

Study sites .

Sampling methods

Results .

Discussion .

References .

313

314
314

314

315
315

317

318

INTRODUCTION

The reptile fauna of Britain consists of three lizard species ( Anguis fragilis,
Lacerta agilis, Lacerta vivipara ) and three snake species ( Coronella austriaca, Matrix
natrix, Vipera berus). The habitats of these reptiles are varied and include
deciduous woodlands, ride verges in forest plantations, scrub, hedgerows, sand
dunes and heathlands. Populations of all six species are found on lowland
heathlands but there are few instances of all six species occurring together in any
other type of plant community. Ericoid shrub communities seem therefore to be
a very important habitat for reptiles, particularly the endangered species ( Lacerta
agilis and Coronella austriaca ), but as with other plant communities and other
animal taxa, the reduction, fragmentation, isolation and change in heathland
communities has had a profound effect on reptile habitats and distribution
patterns (Nature Conservancy Council, 1983).

Although local populations of all six species have diminished rapidly in Britain
(many becoming extinct) over the last few decades and continue to diminish in
size, it has been impossible to quantify changes in population levels on a country-

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I. F. SPELLERBERG

wide basis and difficult, if not impossible, to measure population size of snakes at
a local level. This is because the behaviour of snakes prevents complete
population counts. However, it has been possible to estimate size and density of
some lizard populations, for example House & Spellerberg (1983) estimated the
population density of Lacerta agilis on heathlands at six localities. The population
densities varied from 0.3 to 18.3 lizards per ha and higher densities were found
on disturbed heathland, suggesting that either increased plant species richness or
vegetation structure could be an important component of the reptile habitat.

The aim of this paper is to assess the value of heathlands as habitats for reptiles
with particular reference to vegetation structure.

ENDANGERED REPTILE SPECIES IN BRITAIN

Both Coronella austriaca and Lacerta agilis are totally protected species under the
Wildlife and Countryside Act 1981 and are considered to be endangered in
Britain (Nature Conservancy Council, 1983). The distribution of the smooth
snake is limited to the southern counties and there they are found in heathlands
and other plant communities. The prey of smooth snakes includes lizards and
small mammals, and although nestling young of mice and shrews seem to be an
important component of the smooth snake diet, this snake is considered to be an
opportunistic predator, taking prey according to availability (Goddard, 1984).
Results from radio-telemetry studies indicate that although this species is not
particularly vagile, there are few barriers preventing dispersal of smooth snakes
in heathlands, forests and other plant communities.

The distribution of the L. agilis is fragmented, with a small population in the
north-west of England and many scattered populations in the south. This lizard
is an opportunistic predator, feeding on Coleoptera, Hymenoptera (particularly
ant queens), Araneae, Opiliones, insect larvae and Isopoda (woodlice).
However, there is both seasonal and site variation in their feeding ecology
(Nicholson, 1980). Reproductive requirements of the oviparous L. agilis are
specialized and in June or July a clutch of about six eggs is laid about 7 cm below
the ground surface. The female lizards select nest sites (House & Spellerberg,
1980) but do not protect the nest or care for the young. Large areas of open
heathland provide a range of conditions which are suitable for these nest sites
and incubation of the eggs.

MATERIAL AND METHODS
Study sites

This research is based partly on a new analysis of data collected by House &
Spellerberg (1983), and partly on new held data from two study sites. The study
sites were selected to investigate features of heathlands associated with the lizard
L. agilis but all six species of reptiles occurred on both study sites. The heathland
at study site A was very fragmented and occurred as patches (up to 0.3 ha) of all
growth phases amongst mature pine (mainly Pinus sylvestris ), bracken ( Pteridium
aquilinum ), rhododendron and other garden shrubs. Most patches of heather
contained invasive species and the area supporting L. agilis had a complex plant
community structure as well as a complex topographic structure, created largely

IMPORTANCE OF HEATHLAND HABITATS FOR REPTILES

315

by sand and clay waste. The area (80 ha) was previously subjected to mineral
extraction but is now managed as a nature reserve. By way of contrast, study
site B was on typical, wet and dry heathland (building and mature growth
phases) and acid bog with only small amounts of the 75 ha site subjected to any
disturbance. Plant invasion of the ericoid shrub community was minimal in the
central region where L. agilis and other reptile species occurred.

Sampling methods

The habitat of L. agilis was recorded by way of a 2 m2 quadrat centred on each
lizard sighted (House & Spellerberg, 1983). Most lizards sighted were basking.
The percentage cover (5% steps) of the plant species at six height categories,
percentage bare ground and percentage visible litter was recorded in each
quadrat. The six height categories were as follows: less than 3 cm, 3-10 cm,
10-30 cm, 30-50 cm, 50-100 cm, greater than 100 cm. A total of 76 quadrats
were recorded at site A and 50 at site B.

The following species diversity index (a form of Simpson’s or Yule’s index) was
used to analyse the structural diversity of each quadrat:

D = s(py

This index is a measure of evenness and P; is the proportion of the zth species
(the higher the index, the more even the proportional distribution of species in
the community). The percentage cover of each plant species height category and
also percentage bare ground and visible litter was used as a basis for measuring
the structural diversity. Scoring of percentage cover was in 5% intervals and so
therefore the maximum index was 20 (minimum 1). For example one 2m2
quadrat gave the following results: Calluna vulgaris 30-50 cm (20%), Ulex
europaeus 50-100 cm (10%), Erica cinerea 30-50 cm (20%), bare ground (50%).
The proportions are therefore 20 : 10:20:50 and in the equation are expressed
as follows:

X(0.2)2+ (0.1)2+ (0.2)2+ (0.5) 2
= 2.9.

In this instance, a value of 2.9 indicates an unevenness in the proportional
percentage cover of plant species and bare ground or a low value in terms of
structural diversity.

RESULTS

The seventy-six 2 m2 quadrats at study site A gave 18 species categories
(bryophytes, ‘various herbs’, ‘mixed grasses’ in addition to plant species
identified) and ten species categories resulted from the 50 quadrats at siteB.
Most quadrats (up to 67%) had three or four plant species and very few had
either one or six species. The plant species common to quadrats at both study
sites was similar (Table 1) with Calluna vulgaris, Erica cinerea, bare ground and
plant litter being the most common species and features recorded. In terms of the

316

I. F. SPELLERBERG

Vegetation structure (Diversity Index)

Figure 1. Range and frequency of structural diversity for all quadrats at both sites.

plant species composition of the lizard quadrats, there was little difference
between the two sites.

Vegetation structure can be measured and expressed in many ways. The
several height categories combined with percentage cover of plant species, bare
ground and litter provided a basis for a measure of structure in each quadrat by
way of a diversity index. Quadrats with a high structural diversity contained
several plant species height categories and quadrats with low structural diversity
contained only one or two plant species of uniform height. The range and
frequency of structural diversity for all quadrats at both sites is shown in Fig. 1.

Table 1. Occurrence of plant species in quadrats

Plant species/feature

Percent occurrence in quadrats

Site A

(76 quadrats)

Site B

(50 quadrats)

Calluna vulgaris

85.5%

100 %

Erica cinera

76.3

62.0

Bare ground

67.1

44.0

Litter

56.5

42.0

Ulex europaeus

48.6

28.0

Molinia caerulea

27.6

16.0

Agrostis sp.

27.6

22.0

Bryophytes

27.6

20.0

Erica tetralix

11.8

18.0

Pteridium aquilinum

9.2

10.0

Pinus spp.

9.2

Ulex minor

7.8

40.0

IMPORTANCE OF HEATHLAND HABITATS FOR REPTILES

317

The mean diversity index for site A was 4.4 (S.D. 1.29) and the mean value for
site B was 3.8 (S.D. 1.46). These are significantly different ( t = 2.47, P> . 02 j.

DISCUSSION

House & Spellerberg (1983) have shown that the basking sites of L. agilis in
heathlands are not randomly distributed and that this species seems to select
basking sites. Two important features of heathland communities providing
habitats for L. agilis and other reptile species could be plant species richness and
vegetation structure. The species composition of the quadrats on the two study
sites in this research are very similar but vegetation structure (as measured by a
diversity index) was significantly different. Fewer suitable conditions at site B
would support a smaller population of lizards and this is supported by the
difference in lizard population density: 9.2 ha at site A; 0.3 at site B House &
Spellerberg, 1983).

The main ecological requirements of reptiles include space, food, heat (for
maintenance of precise, body temperatures) and protection from both predators
and unfavourable weather conditions. In general, snakes are more mobile
(vagile) than lizards and therefore space requirements (expressed as home
ranges) are much larger than home ranges of lizards (Spellerberg, 1988a). The
six species of reptiles eat a range of prey from insects to small mammals
(Table 2). Reproduction, digestion, rate of growth, visual acuity, locomotion
and other forms of behaviour are temperature dependent and therefore reptiles
devote much time to behavioural thermoregulation. The structure of ericoid
shrub communities provides protection from some predators but of more
importance the structure is particularly suitable for basking and for precise
regulation of body temperature. Alternating between sunlit and shaded areas is a
basic form of behavioural thermoregulation common amongst reptiles and is a
means of control of heat uptake for precise regulation of body temperature. The
mosaic of sunlit and shaded areas within heathland communities and within
ericoid shrubs enables reptiles to shuttle between these areas, making optimum
use of the heathland microclimate.

Table 2. Distribution, size, reproduction and some ecological characteristics of Britain's reptiles

An guis
fr agilis

Lacerta

agilis

Lacerta

vivipara

Coronella

austriaca

Natrix

natrix

Vipera

berus

Distribution

ESW

E

EHSW

E

EW

ESW

Weight (g)

15

9.7

3.6

34

98

76

Length (cm)

16

7.8

5.8

42

60

45

Reproduction

V

O

V

V

O

V

Tb (°C)

23

31

32

27

26

30

C (°C)

2.7

3.0

-0.9

0.3

1.6

— 0.5

Prey

Slugs

Insects

Spiders

Nestlings

Fish

Small

Worms

Spiders

Insects

Small mammals
Lizards

Amphibians
Small mammals

mammals

Lizards

E, England; S, Scotland; W, Wales; H, Ireland.

V, Viviparous; O, oviparous; Tb, mean body temperature.
C, Lowest temperature for activity.

From Spellerberg (1988b).

318

I. F. SPELLERBERG

If L. agilis is selecting basking sites with a high vegetation structural diversity,
the benefits would probably be linked to behavioural thermoregulation and food
requirements. Utilization of sites with maximum variation in structure would
allow the lizards to alternatively bask and seek shade with minimum costs. As
well as providing suitable microclimates for L. agilis and other reptiles, a
structurally complex heathland site may also support higher levels of
invertebrate prey items which in turn could contribute to the presence of higher
levels of small mammal communities. Undisturbed, open expanses of lowland
heathlands probably support poor populations of small mammals (Webb, 1986)
but in areas where the typical ericoid shrub community has been altered with
invading plant species and where the ground has been disturbed as a result of the
construction of embankments and other earthworks, small mammals may be
more abundant. An abundance of small mammals, and structurally complex
vegetation and topography would form the basis of habitats suitable for
C. austriaca and the other two snake species.

Where reptiles do occur on heathlands, management directed at the
conservation of heathland plant communities would not be detrimental to the
reptile populations. It is suggested that open heathland sites should continue to
be managed with a view to the normal considerations and protection of
heathland floristics and more importantly structure. Sparse populations of
L. agilis will survive in such areas but higher densities of lizards can occur if
scrub, bracken, trees and various forms of ground disturbance are included in
the area. An overriding problem for conservation of wildlife on heathlands is the
continual process of reduction in area, fragmentation and isolation of this plant
community. The remaining fragments of heathland cannot all be managed to
satisfy the conservation needs of all taxa and therefore there seems to be a need
for compromise and possibly the establishment of priorities in terms of
management strategies. Restoration of heathlands (now well researched; British
Gas, 1988) and possibly recreation of this diminishing resource may alleviate
such difficulties.

REFERENCES

BRITISFI GAS, 1988. Heathland Restoration: a Handbook of Techniques. Southampton: British Gas pic.

GODDARD, P., 1984. Morphology, growth, food habits and population characteristics of the smooth snake
Coronella austriaca in southern Britain. Journal of goology, London, 204: 241-257.

HOUSE, S. M. & SPELLERBERG, I. F., 1980. Ecological factors determining the selection of egg incubation
sites by Lacerta agilis L. in southern England. In Proceedings of the European Herpetological Symposium, CWLP
Oxford 1980: 41—54.

HOUSE, S. M. & SPELLERBERG, I. F., 1983. Ecology and conservation of the sand lizard ( Lacerta agilis L.)
habitat in southern England. Journal of Applied Ecology, 20: 417-437.

NATURE CONSERVANCY COUNCIL, 1983. The ecology and conservation of amphibian and reptile
species endangered in Britain. London: Wildlife Advisory Branch, NCC.

NICHOLSON, A. M., 1980. Ecology of the sand lizard (Lacerta agilis L.) in southern England and comparisons with
the common lizard Lacerta vivipara Jacquin. Unpublished Ph.D. Thesis of the University of Southampton.

SPELLERBERG, I. F., 1988a. Ecology and management of reptile populations in forests. Quarterly Journal of
Forestry, 82: 99-109.

SPELLERBERG, I. F., 1988b. Management of forest habitats for reptiles and amphibians. In D. C. Jardine
(Ed.), Wildlife Management in Forests: 83-91. Institute of Chartered Foresters.

WEBB, N., 1986. Heathlands. London: Collins.

Botanical Journal of the Linnean Society (1989), 101: 319-327. With 2 figures

The Ericoideae and the southern African
heathers

E. G. H. OLIVER

Botanical Research Unit, P. 0. Box 471 , Stellenbosch 7600, Republic of South Africa

OLIVER, E. G. H., 1989. The Ericoideae and the southern African heathers. The subfamily
Ericoideae (Ericaceae) containing the true heathers and heaths has been a group long recognized as
a sound natural entity. With work on the southern African genera and species which comprise
approximately 95% of the subfamily well in progress, a reassessment of the number of genera has
become necessary because of the considerable variation recorded in, and the postulated polyphyletic
origin of, the capsular genera. Changes envisaged will affect the whole concept of the heaths within
Africa. I he genus Philippia Klotzsch has been reduced to synonymy under Erica L. and it is shown
that the case for a similar action is very strong for Blaeria L. and Ericinella Klotzsch. The position of
the monotypic European genus, Bruckenthalia Reichb., is also affected but remains unresolved.

ADDITIONAL KEY WORDS:- Blaeria - Bruckenthalia - Erica - Ericinella - Philippia - taxonomy.

CONTENTS

Introduction . 319

Calluneae . 320

Ericeae . 320

Erica . 320

Philippia . 322

Blaeria . 323

Ericinella . 324

Bruckenthalia . 325

Conclusions . 325

Key to tribes of the Ericoideae . 326

Constituents and distribution of tribes . 326

Acknowledgements . 327

References . 327

INTRODUCTION

The subdivision of the family Ericaceae per se has not received much attention
other than as part of a worldwide treatment of families and genera (Don, 1834;
Bentham, 1839, 1876; Drude, 1897). Klotzsch (1834) was the first to look at
heathers on their own. He divided them into three tribes based on the degree of
fusion of the stamens. Bentham in treating the whole family for de Candolle's
Prodromus (de Candolle, 1839) and later for the Genera Plantarunr (Bentham,
1876) introduced the subdivisions Euericeae and Salaxideae at subtribal level
based on the carpels and their complement. Drude retained Benthanrs
classification for Engler & Prantfs Die JVaturlichen Pfanzenfamilien Drude, 1897),
but using the updated terminology as recognized today, i.e. the subfamily
Ericoideae with two tribes, Ericeae and Salaxideae.

319

0024—4074/89/110319 + 09 $03.00/0 © 1989 The Linnean Society of London

320

E. G. H. OLIVER

This work remained as the standard treatment of the subfamily for the next 80
years until Watson, Williams & Lance (1967) queried this classification. They
looked at a fairly wide range of characters but in only a small sample of the
family. Using a computer-assisted numerical analysis they suggested a new
system which contained two tribes within the subfamily ‘Ericoids’, tribe 1
containing Calluna and, surprisingly, Cassiope from the Arbutoideae and tribe 2
with all of the rest of the subfamily. Stevens (1969, 1971) did a world-wide and
more detailed assessment of the family. He rejected the inclusion by Watson et al.
(1967) of Cassiope within the heather subfamily even though its members look
very heath-like. He proposed the subdivision of the Ericoideae into three tribes,
Calluneae, Ericeae and Salaxideae. The latter two he retained as construed by
Bentham and Drude on the grounds of insufficient data to suggest otherwise.
This is the classification of the subfamily most accepted at present.

CALLUNEAE

Calluna is an enigmatic genus because of its numerous bracteoles, sagittate
leaves, pith type, adaxial leaf stomata and septicidal capsule. None of these
characters occurs within the rest of the genera in the subfamily. Recognition of
this very distinct genus at a high level is certainly justifiable. Stevens chose to
isolate the genus at tribal level, but is could be argued that Calluna should be
placed in its own subfamily thus rendering the Ericoideae more uniform.

ERICEAE

The rest of the heather subfamily can be retained with the subdivision into
Ericeae and Salaxideae, but not based on ovary complement as the sole
distinguishing criterion as has been done to date. My investigations suggest the
structure of the fruit as the criterion, i.e. dehiscent vs. indehiscent. This will
necessitate a reallocation of genera between the tribes. All the genera possessing
a dehiscent capsule would belong to the Ericeae and all are widespread in Africa
and Europe (Fig. 1). The indehiscent fruited genera having either a berry or
drupe would be placed in the Salaxideae. These are all endemic in the south¬
western and southern Cape Province in southern Africa and are more advanced,
recently evolved, genera which can be derived from a basic ericoid groundplan
by reduction in or fusion of parts of each whorl.

I propose to discuss here only the capsular genera in the Ericeae as currently
accepted in Flora Europaea (Webb, 1972: Webb & Rix, 1972), Flora of West
Tropical Africa (Ross, 1963), Flore de Cameroun (Letouzey, 1970), Flora fambesiaca
(Ross, 1983), Flore des Mascareignes (Friedmann, 1981) and List of species of
southern African plants (Oliver 1987a). These are of more relevance to a British
audience and also exhibit some remarkable variation patterns which will have a
considerable effect on our acceptance of these genera. The genera are Erica L.,
Philippia Klotzsch, Blaeria L., Ericinella Klotzsch and Bruckenthalia Reichb.

Erica

Erica, by far the largest genus in the subfamily with c. 670 species at present,
exhibits the basic groundplan of the ericoids with B1 ,br2,K4,C(4),A8,G(4),Soo,

SOUTHERN AFRICAN HEATHERS

321

Figure 1. Maps showing the approximate native distribution of the capsular genera. Erica, Philippia,
Blaeria, Ericinella and Bruckenthalia. Figures represent the estimated number of species per region.

322

E. G. H. OLIVER

i.e. bract 1, bracteoles 2, (K) calyx free 4, corolla fused 4, androecium (stamens)
free 8, gynoecium superior 4-locular and seeds numerous, and this with,
remarkably, very few exceptions. Most of the variation within the genus occurs
in the structure of the inflorescence, in the size, shape and colour of the calyx and
of the corolla and in the shape and adornments of the anthers.

The other capsular genera can be regarded as offshoots closely related to Erica.
These capsular genera are currently being revised for inclusion in the Flora of
southern Africa.

Philippia

The results of a detailed study of the southern African species of this pan-
African genus have recently been published (Oliver, 1988). However, I will
repeat the salient points to emphasize the generic problems within the capsular
genera.

Philippia was described by Klotzsch in 1834 and has been maintained as a
genus in all subsequent regional African floras and the only complete revision
(Aim & Fries, 1927) based on the possession of a fully recaulescent bract and no
bracteoles producing a zygomorphic 4-partite or -lobed calyx, a condition found
in most of the c. 65 species (Fig. 2).

However, problems in the distinction between Philippia and Erica were noted
by Aim & Fries (1927.) They referred on a number of occasions to
“iibergangsformen, -typen" but proceeded to retain the genus.

Investigations in the southern African material have revealed a complete series
of intermediates within a few species, namely P. pallida L. Guthrie, P.stokoei
L. Guthrie, P. tristis H. Boh, E.peltata Andr., E. accommodata Klotzsch var.
ebracteata H. Boh, H. caespitosa Hilliard & Burtt, E. hispidula L., E. inops H. Boh,
E. ebracteata H. Boh, E.anomala Hilliard & Burtt, E sparsa Lodd., E.alticola
H. Boh and E. dissimulans Hilliard & Burtt. The most remarkable variation data
are shown in Table 1.

Fhe variation recorded was such that either end of the range could be located
under two separate species in two separate genera and, depending on the flower
looked at, a collection could be placed either in Erica or in Philippia. There were
in fact two places in which to hie material in the herbarium! A brief reference to
collections of Philippia (BOL, MO, PRE) and to literature on the Ericoideae
from tropical Africa (Pichi-Sermolli & Heiniger, 1953; Ross, 1957, 1983) and
from the Mascarenes (Friedmann, 1981) revealed a similar variation pattern in

Ericoid

Ericord/Philippioid
intermediate

Philippioid

Figure 2. Series of diagrams showing stages in the recaulescence of the bract up the pedicel in the
Ericoideae from axial (aB) on the left to totally recaulescent (RB) on the right.

SOUTHERN AFRICAN HEATHERS

323

Table 1. Distribution of bract/bracteole/calyx characters in
six species of Erica (Ericoideae) in southern Africa3

Species

Erica

rB, 2br, K4

Erica/ Philippia
rB, Obr, K4 or 3

Philippia
RB, K3

E. anomala

0

40

60

E. dissimulans

2

98

0

E. caespitosa

3

83

14

E. ebracteata

11

46

43

E. peltatah
( = P. pallida)
Ashton

16

40

44

Swellendam

0

38

62

Niekerkshek

3

30

67

Others

22

38

40

E. spars a

2

94

4

aFigures express the percentage of flowers in the samples
examined.

bAnalysis of three population samples and of 15 collections from
the complete range of the species.

the B/br/K arrangement, but perhaps only to the same degree in the East
African P. keniensis S. Moore and E. kingaensis Engl.

Several additional features are very relevant to the existence of Philippia. Most
species of Philippia have their closest allies within the section Arsace in Erica.
However, some such as P. pallida jE. peltata and P. stokoei\E. lasciva, are more
closely related to ericas in other sections than they are to species of Philippia.
Similarly, it is clear that the philippias of East Africa are more closely related to
East African ericas than to southern African philippias. Aim & Fries (1927: 1 1)
stated clearly that they could not find any close relationship between the
Madagascan/Mascarene species and the continental species nor between the
tropical African and the Cape species. This clearly points to a polyphyletic origin
for the genus.

Blaeria

This genus was created by Linnaeus as early as 1737 and since then has
always been recognized in African Floras. It differs from Erica in only one
character, four vs. eight stamens, and since Linnaeus’ time any ericoid with four
stamens has often been placed in Blaeria. Problems with the stamen complement
have been known for some time, the classic case being E. eylesii L.Bol. var.
blaeriodes Wild from the Zimbabwean highlands (Wild, 1954). Ross (1980: 137)
stated that within the species complex, which includes E. eylesii, even the
possession of four stamens instead of eight, the feature distinguishing Blaeria from
Erica, could not be used as a distinguishing criterion because of plants with a
complete range of stamen number.

In southern Africa I have come across problems in some species of both Erica
and Blaeria (Table 2). From the literature this is clearly the case to the north in
tropical Africa (Ross, 1957) where there is a variation in stamen complement
that places flowers of a single specimen in either genus. With the inclusion of

324

E. G. H. OLIVER

Table 2. Variation in generic delimiting characters in some
species of Blaeria and Erica

Taxa

Number of stamens

Blaeria (most species)

4

Erica tetragona L. fil.

4 (6) 8

Erica jiliformis Salisb.

4 (6) 8

Erica pleiotricha S. Moore

var. pleiotricha

(7) 8

var. blaeriodes (Wild) R. Ross

4-8

Erica parvula Guth. & Bold

8

Blaeria campanulata

4-(8)

Blaeria equisetifolia (Salisb.) Don

4-(8)

Erica sensu latoh

Philippia nyassana

4 (5)

Philippia mannii

(5) 6 (7 or 8)

Philippia hexandra

6 (7 or 8)

“Species complex of very closely related taxa.

‘The genus Erica when Philippia is reduced to synonymy.

Philippia in Erica (Oliver, 1988) the problem is compounded as there is
considerable variation in the tropical species. Philippia ny as sana Aim & Fries has
mainly four stamens but occasionally five, P. mannii (Hook, hi.) Aim & Fries
usually six, occasionally five, seven or eight, P. benguellensis (Welw. ex Engl.)
Britten eight, occasionally five to nine and P. hexandra S. Aloore six, occasionally
seven or eight stamens. Ross (1957: 735) also mentioned the problem in Erica
when he noted that some specimens of if. arborea L. from East Africa have four or
five stamens in most Bowers.

Blaeria exhibits a somewhat anomalous distribution compared to Erica and
Philippia (Fig. 1). A few species are widespread in tropical, subtropical and
temperate Africa. The genus is absent between the highlands of Zimbabwe and
the mountains of the southern Cape Province with no representatives on the
Drakensberg where both Erica and Philippia occur.

Within the Cape it is clearly evident that the species bear close relationships
with local species of Erica and are in no way closely related to the other species of
Blaeria far to the north. As was the case with Philippia one can again postulate a
polyphyletic origin for the genus.

Ericinella

The above discussion then leads on to the last of the African capsular genera,
Ericinella Klotzsch, described in 1838 and a smaller genus not as widespread as
the other two. It has up to now been distinguished by a totally recaulescent bract
as in Philippia and only four, rarely five stamens as in Blaeria and an ovary of
G3(4). From the aforegoing discussion it is immediately evident that problems
must therefore occur in recognizing Ericinella.

Ross (1983: 158) could separate the single tropical species only on the anther
appendages and the size of the stigma both of which are frequently used as
specific characters in the rest of the subfamily. This was because P. nyassana and
Ericinella microdonta (C. H. Wright) Aim & Fries from Mlanje both have a totally
recaulescent bract and four stamens. Philippia mannii widespread in tropical

SOUTHERN AFRICAN HEATHERS

325

Africa, has five to eight stamens and an ovary of G3 or G4. Ross (1980: 126; also
noted that in B. kingaensis the bracteoles can often be absent as occurs in the
Erica! Philippia intermediate state (Fig. 2).

In the Cape Province the three species of Ericinella appeared to be quite
distinct from the other capsular ericoids in having four stamens and an ovary
complement ofG3. However, recent studies in the Cape blaerias brought to light
variation within B. campanulata Benth. with four, five or six stamens and an ovary
of G3. So here again there is an overlap in generic diagnostic features. As with
Blaeria the genus Ericinella has an anomalous distribution with a large gap
occurring between the three Cape species and the single species, E. microdonta ,
from Malawi and south-western Tanzania. This latter species appears to be
more closely related to the tropical Erica! Philippia! Blaeria complex than to the
Cape species of Ericinella suggesting again polyphylesis.

Bruckenthalia

The last of the capsular genera in the Ericoideae is another enigmatic
European genus, namely Bruckenthalia. This monotypic genus is confined to
Europe, in the south-eastern parts only and northern Turkey. It is occasionally
cultivated in Britain.

The genus is easily distinguishable from Erica in Europe (Webb, 1972) by
having no bracteoles and a partially-fused calyx. However, working on a global
classification of the ericoid genera one encounters problems with the southern
African species of Erica. There are seven Cape ericas in the section Gamochlamys
characterized by a partially-fused calyx (Baker & Oliver, 1967) with one species,
E. newdigatei Dulfer, having a calyx almost identical to that in Bruckenthalia. With
Philippia included within Erica an additional approximately 35 species possess a
partially-joined calyx.

The absence of the two bracteoles is very much similar to the situation
mentioned earlier (Fig. 2) in the Erica! Philippia intermediate except that the
bract is always in the axial position as aB. However, E. alticola H. Bol. in the
Transvaal has been found to possess flowers mostly of the aB,Obr type and a
very similar inflorescence to that occurring in Bruckenthalia which appears
invariably to have flowers of the aB,Obr type. Populations of Bruckenthalia will
need to be examined in detail to ascertain whether this last statement is in fact
true.

One interesting feature of Bruckenthalia is the chromosome number. The few
ericoids, c. 5%, that have been looked at so far have n— 12 for Erica, n = 8 for
Calluna and n= 18 for Bruckenthalia (Callan, 1941). A nurseryman near Bremen in
West Germany, K. Kramer (personal communication) has managed very
recently to produce offspring from a Bruckenthalia x Erica cross (B. spiculifolia
(Salisb.) Reichb. x E.carnea L.). An investigation of the chromosomes should
prove most useful. Material of Bruckenthalia is currently being cultivated at the
National Botanic Gardens, Kirstenbosch, for further studies.

CONCLUSIONS

From the above discussion it is clearly evident that the current delimitation of
genera within the capsular members of the Ericoideae is very unsatisfactory. It is
shown that the variation patterns found within certain species of all the genera

326

E. G. H. OLIVER

produce situations where the degree of overlap between the genera renders their
recognition as distinct entities unacceptable or at least very tenuous. The
situation is such that certain specific taxa can easily be placed in either of two
genera.

In three of the genera, Philippia, Blaeria and Ericinella, the relationships of the
species do not all lie within their current generic boundaries, but rather with
species alliances in another genus. This situation is compounded by the
geographic separation of the species into regional alliances. Polyphyletic origins
for the above three genera as presently construed are strongly indicated by all
the evidence. The genera are clearly unnatural groupings of species.

The decision to reduce the genus Philippia to synonymy under Erica for the
southern African region has been published and the nomenclatural changes have
been made (Oliver, 1987b, 1988). The nomenclatural changes for tropical
Africa, Madagascar and the Mascarenes need still to be made. From the brief
arguments put forward above, the cases of Blaeria and of Ericinella are clearly
similar. However, more detailed papers setting out each case and dealing with
the nomenclature will be published elsewhere.

The situation with Bruckenthalia remains unresolved because further studies on
any variation in the distinguishing characters and an investigation of the hybrids
with ericas should be undertaken before a final decision on the validity of the
genus is taken.

As a result of my investigations in the Ericoideae some drastic changes will
have to take place to rationalize the classification of the subfamily. The retention
of the three tribes listed by Stevens (1971) is endorsed but with a
recircumscription of the Ericeae and Salaxideae and consequent reallocation of
genera. The tribe Ericeae could eventually consist of the single megagenus Erica.

KEY TO TRIBES OF THE ERICOIDEAE

Leaves sagittate, bracteoles 6 or more
Leaves not sagittate, bracteoles 0-2
Fruit a dehiscent capsule
Fruit an indehiscent drupe or berry

Calluneae

Ericeae

Salaxideae

CONSTITUENTS AND DISTRIBUTION OF TRIBES

Calluneae: one genus, Calluna, with one species widespread in Europe up to the
Ural Mountains.

Ericeae: two genera — Erica with approximately 735 species widespread in
Europe including the Atlantic islands, the Middle East (Turkey, Syria and
Lebanon), the Arabian Peninsula (Yemen), the whole of Africa, Madagascar
and the Mascarenes, 92% of the species occurring in the Cape
Province — Bruckenthalia with one species confined to south-eastern Europe and
Turkey.

Salaxideae: approximately 14 genera with 130 species all confined to the
southern Cape Province.

SOUTHERN AFRICAN HEATHERS

327

ACKNOWLEDGEMENTS

I should like to express my thanks to the Botanical Society of the British Isles
and Linnean Society of London for inviting me to participate in this Symposium
and to the South African Nature Foundation (WWF) for financial support. The
exhibit of fresh material supplied by the National Botanic Gardens,
Kirstenbosch, is gratefully acknowledged.

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