Phytoneuron

Pruski, J.F. 2012. Compositae of Central Am erica-I. The tussilaginoid g
generic delimitation, and exclusion of senecioid Senecio cuchumatanensk
2012. ISSN 2153 733X

COMPOSITAE OF CENTRAL AMERICA-!

THE TUSSILAGINOID GENUS ROBINSONECIO (SENECIONEAE),

MICROCHARACTERS, GENERIC DELIMITATION, AND EXCLUSION OF

SENECIOID SENECIO CUCHUMATANENSIS

John F. Pruski

Missouri Botanical Garden

P.O. Box 299
St. Louis, Missouri 63166

ABSTRACT

Robinsonecio has tussilaginoid microeharaeters and is represented in Central America by a
single species, the generitype Robinsonecio gerberifolius. A lectotype is designated for Senecio
gerberifolius. Senecio cuchumaianensis of Guatemala has been suggested to be a congener of R.
gerberifolius, but. its senecioid microeharaeters are found here to exclude it from Robinsonecio.

KEY WORDS: Asteraceae, Central America, Compositae, Guatemala, Mexico, Robinsonecio,
Robinsonecio gerberifolius, Senecio cuchumaianensis, Senecio gerberifolius, Senecioneae.

Robinsonecio T.M. Barkley & Janovec (Compositae; Senecioneae: Tussilagininae) was
segregated from the Lugentes subgroup (Barkley 1985) of Senecio L. (Senecioninae) based on its
tussilaginoid microeharaeters (often called "cacalioid" microeharaeters, e.g., Robinson & Brettell
1973b, 1973b; Wetter 1983). The genus includes 2 species — R. gerberifolius (Sch. Bip. ex Hemsl.)
T.M. Barkley & Janovec (alpine areas in southeastern Mexico and western Guatemala) and R.
porphyresthes (T.M Barkley) T.M. Barkley & Janovec (Tamaulipas, Mexico), Barkley and Janovec
(1996) noted that in Robinsonecio each style branch has a continuous stigmatic surface and that its
anther collars are cylindrical, each character a tussilaginoid trait (Koyama 1967; Robinson & Brettell
1973b; Nordenstam 1978; Wetter 1983). While many tussilaginoid Senecioneae have polarized
endothecial cell wall thickenings (Dormer 1962; Robinson & Brettell 1973b; Nordenstam 1978;
Wetter 1983), Barkley and Janovec (1996) characterized the endothecium of R. gerberifolius as
polarized and that of R. porphyresthes as radial.

Hemsley (1881) described Robinsonecio gerberifolius (sub Senecio) as having pubescent
cypselae, whereas Barkley and Janovec (1996) gave the cypselae as glabrous. Williams (1975) allied
R. gerberifolius (sub Senecio) with 5. cuchumaianensis, and indeed these two species are subscapose
herbs known only from similar montane habitats. Barkley and Janovec (1996) noted that S.
cuchumaianensis is similar in "gross aspect" to Robinsonecio, but they did not provide a
nomenclatural transfer commenting that this must "await further information." Subsequently, Barkley
(en schedula MO) annotated the type and paratype material of S. cuchumaianensis as Robinsonecio
using a non-published binomial based on S. cuchumaianensis.

The present study supports Robinsonecio as belonging to the tussilaginoid generic alliance
(subtribe Tussilagininae), evidenced by its cylindrical anther collars (fig. 1A-B) that are no broader
than the filaments and by its style branches (fig, IE) each with a continuous stigmatic surface.
However, I find R. gerberifolius to have adaxial endothecial tissue composed of elongate cells each
with a radial cell wall thickening pattern (fig. 1C), and with only a thin line of elongate cells of the
non-polliniferous connate zone between adjacent anther thecae as having polar thickenings (fig. ID).
It should be noted that while, for example, Jeffrey and Chen (1984) characterized the Tussilagininae

Figure 1. Micro characters of Robinsonecio gerberif alius . A. Individual anther the ca showing abaxial face of
anther collar -filament juncture (arrow) and apically acute anther appendage. B. Ahaxial close-up of the
cylindrical iussiiaginoid anlher collars with arrow pointing to (basal portion or} connate zone between two
adjacent anther thecae. C. Medial adaxial endoihecial tissue with radially thickened (transversely ribbed) cell
walls. D. Medial adaxia! border ofindi vidua! anlher showing connate zone cells with thickenings at their poles.
E. Style showing slightly dilated stipitate base sitting atop the basal nectary ralher than immersed within
nectary. F. Close-up of style bsse, nectary, arid apical portion of a pilose ovary. Q. Glabrous evpsela. (A-D, G
from Pruski &. Ortiz 4163, MO; E-F from Garcia ct at. 1901, MO). [Scale bars: A 0.3 mm; B 0.1 mm; C, D 20
urn; E2 mm; F 0.2 mm; G 1 mm.]

as having polarized endothecial tissue composed of nearly isodismietric ceils (as indeed is a tendency,
especially in Asian genera of the subtribe), both Dormer (1962) and Wetter (1983) noted some
intraspecific variation in this character. Although Robinsonecio, by radiate capitula and yellow disk
corollas with lobes shorter than the throats, does not match the "cacalioid condition" (Pippen 1968),
several Central American genera subsequently accepted as tussilaginoid (Barkley et al. 1996) have
radiate capitula, yellow corollas, and short disk corolla lobes. The disk corolla lobes of R.
gerberifblius are triangular-lanceolate to lanceolate and its anther appendages are acute apically (fig.
1A). The styles of R. gerberifblius are only slightly dilated at the base. This basal stylar node is not
immersed in the nectar}', but rather sits on a stipe atop the nectary (fig. 1E-F) as in the free
stylopodium type 1 in Wetter (1983: figs. !4 and 17). The ovaries and cypselae of R. gerberifblius
have carpopodia that; as noted by Barkley and Janovec (1996), are moderately developed (fig. 1G).
As described by Garcia-Perez (2001), the ovaries and cypselae of R. gerberifblius vary from being
glabrous to pilose (fig. 1F-G). Elsewhere, for example, Koyama (1967) noted similar - intraspecific
cypselae indumentum variation in Asian taxa.

©-)

Figure 2. Microcharacters of Senecio cuchumatanensis. A. Balusterform (seneci

the anther on the left the abaxial junction (arrow) with the narrower filaments.

tissue with radially thickened cell walls. C. Broadly rounded anther appendage apices. D. Style showing

abruptly dilated st\ie base (not showing nectary), (all from Steyermark 501 1 7, MO, a paratype). [Scale bars:

A, C 0.2 mm; B 30 urn; D 2 mm.]

These microcharacters of Robinsonecio contrast with those of S. cuchumatanensis, which has
the senecioid microcharacters of (1) moderately balusterform (distal cells somewhat quadrangular and
basal cells isodiametric, with shght cell wall thickening basahy) anther collars broader than the
filaments (fig. 2A) and (2) each style branch (fig. 2D) with a 2-banded stigmatic surface with clear
"morphological distinction between the cells" (Wetter 1983) of the stigmatic surfaces and those of the
medial groove. Senecio cuchumatanensis differs further from Robinsonecio by triangular disk corolla
lobes, apically broadly rounded anther appendages (fig. 2C), and by its abruptly dilated lai'ge-celled
style bases (fig. 2D) that arise within the low annular (slightly darker colored, slightly wider)
nectaries. This stylopodium type more or less matches the "partially immersed" configuration seen in.
Wetter (1983: fig. 16), but the style base in S. cuchumatanensis is much more dilated than hi any of
the six tussilaginoid photographs in Wetter (1983: figs. 14-19). Although Wetter (1983) notes
stylopodial features as notoriously variable, here it appears to be useful taxonomically. Senecio
cuchumatanensis may thus be safely excluded from Robinsonecio and retained in Senecio. Although
S. cuchumatanensis has a radial endothecial pattern (fig. 2B) similar to that typical for Robinsonecio
(fig. 1C), nearly all senecioid genera and most American tussilaginoid genera share tliis radial
endothecial condition.

The purpose of the present account is to illustrate the microcharacters used to circumscribe
Robinsonecio, to provide an expanded description of R. gerberifolius that may be inserted into
Williams (1976), and to show that on the basis of microcharacters S. cuchumatanensis should not
continue to be aligned with Robinsonecio. While both R. gerberifolius and S. cuchumatanensis are
subscapose herbs occurring in the Sierra de los Cuchumatanes, with S. cuchumatanensis endemic to
this range, the similarities between these two species are basically incidental.

y«

ml

Pruski: Robinsonecio

ROBINSONECIO T.M. Barkley & Janovec, Sida 17: 79. 1996. TYPE: Senecio gerberifolius Sell.
Bip. ex Hems]. [= Robinsonecio gerberifolius (Seh. Bip. ex Hemsl.) T.M. Barkley &
Janovec],

Small subscapose perennial rosulate herbs, caudex thick, root fibrous; scapes l(-2) per
plant, basally copiously floccose to lanate, sometimes glabrate distally, rosette prominent (Fig. 3),
cauline leaves remote and reduced; herbage lanate to glabrate, eglandular. Rosette leaves spirally

alternate; blade secondary venation indistinct, base gradually attenuate onto narrowly winged petiolar
base that is dilated near caudex, margins entire to remotely denticulate, sometimes revolute, surfaces
often discolorous. Cauline leaves sessile, margins entire. Capitulescence erect or ascending, laxly
cymose, 1-6-capitulate. Capitula radiate; involucre campanulate, irregularly and loosely calyculate;
phyllaries 13-20, imbricate, arachnoid or villous at least proximally, often glabrate distally, margins
of inner phyllaries sometimes broadly scarious; receptacle solid. Ray florets pistillate; corolla yellow
or golden-yellow, limb well-exserted. Disk florets bisexual, slightly exserted from involucre; corolla
narrowly funnelform, yellow, glabrous, tube and limb subequal, lobes triangular-lanceolate to
lanceolate, ascending to sometimes slightly spreading, with or without a medial resin duct; anthers
mostly included, collar cylindrical, equal in diameter to filaments, thecae base obtuse, not caudate,
endothecial tissue typically radial, apical appendage triangular, acute apically; style base cylindrical
to slightly dilated and sitting atop the basal nectary rather than immersed within nectary, branches
weakly exserted, slightly recurved, apex obtuse to truncate, papillose in a subapical-abaxial semicircle
below apex, stigmatic surface continuous. Cypselae cylindrical, 10-nerved, base gradually narrowed,
carpopodium prominent; pappus bristles of rays and disks similar, white, barbellate, about as long as
the disk corollas, x = 30.

Robinsonecio is defined primarily by the tussilaginoid microcharacters of cylindrical anther
collars and continuous stigmatic surfaces, and secondarily by subscapose habit, radiate capitula,
yellow disk corollas with triangular-lanceolate lobes, and acute anther appendage apices. The genus
consists of two species and is centered in Mexico, but the following species is disjunct from Pico de
Orizaba to the Sierra de los Cuchumatanes in Guatemala.

ROBINSONECIO GERBERIFOLIUS (Sch. Bip. ex Hemsl.) T.M. Barkley & Janovec, Sida 17: 79.
1996. Senecio gerberifolius Sch. Bip. ex Hemsl., Biol. Cent.-Amer., Bot. 2: 240. 1881, as
"gerberaefolius." LECTOTYPE (designated here): MEXICO. Veraeruz-Puebla border. Pico

de Orizaba, 3500 m (as "11500 ft"), 7\pr 1838, Linden 487 (lectotype: K, left-hand side, photo
in MO; isolectotype: GH). (Figs. 1, 3^1).

Herbs 15-33 cm tall, scapes usually 1-3-leaved. Rosette leaves long-petiolariform, spreading
to patent; blade 2-15 * 0.7-2.5(-3.5) cm, narrowly oblanceolate m uHiinsr to <-patulale oi ob pate
subcoriaceous, midrib sometimes impressed adaxially, apex acute to less commonly obtuse, slightly
to obviously discolorous. adaxial surface gray-green to green, sometimes nitidous, arachnoid-floccose
to glabrate, abaxial surface grayish- white, tomentose to lanate; petiolar base 1-8 cm long. Cauline
leaves 1-3; blade 2-7 cm long, lanceolate or infrequently oblanceolate, semiamplexicaule.
Capitulescence scape 14-31.2 cm long, striate or few-angled, densely floccose or lanate to
sometimes arachnoid or glabrate in patches; peduncles (when pluricephalous) l-8(-10) cm long.
Capitula 10-18 mm tall; involucre 10-15 mm diam,. loosely arachnoid-floccose in bud; phyllaries
ca. 13, 8-13 x 2-3.5 mm, elliptic-lanceolate to narrowly ovate, typically greenish-yellow throughout,
pluristriate, arachnoid proximally and glabrate distally, apex acute, sometimes purplish; calycular
bracteoles l-5(-7), 7-12 x 0.7-1.1 mm, about 3/4 as long as the phyllaries, linear-lanceolate, green;
receptacle convex, foveolate. Ray florets usually 13(1 1-15); corolla tube 5-6 mm long, limb 11-15
x 3-4 mm, elliptic-lanceolate, 4-9-nerved, 3-denticulate, apical teeth 0.1-0.3 mm long. Disk florets
35-65; corolla 8-10 mm long, lobes 1-1.6 mm long, typically with a medial resin duct; anthers 2.5-3

Pruski: Robinsonecio

mm long, endothecial tissue radial or sometimes polarized, non-polliniferous connate zone between
anthers usual with cells thickened at poles; style branches 1.2-1.5 mm long. Cypselae 3-4 mm long,
brown, glabrous to pilose, trichomes to 0.5+ mm long; pappus 6.5-8.5 mm long. In = 60.

Representor! >■ spiciinen<> examined MEXICO. Mexico. Telapon, 4000 m, Dec 1928,
Lyonnet 395 (MO, NY); Ixtaccihuatl, subalpine region, Oct 1905, Purpus 1516 (F, MO, NY).
Puebla. Slopes of Ixtaccihuatl above Huejotzingo, 4260 m, 21 Oct 1945, Hernandez & Sharp X-154
(MO). Veracruz. Cerca de la Roca del Cofre Perote, 4000 m, 28 Aug 1971, Dorantes 324 (MO,
XAL); Cima del Volein Cofre de Perote, 4180 m, 2 Oct 1984, Garcia el al. 1901 (MO). Veracruz-
Puebla border. Pico de Orizaba, 3048^1552 m (as 10000-15300 ft.), Liebmann 8853 (species
number 140) (C [photograph sub Macbride negative #22623 in MO], K); Pico de Orizaba, volcanic
ash, ca. 4 km N of summit, 3925 m, 15 Feb 2007, Pruski & Ortiz 4163 (MO). GUATEMALA.
Huehuetenango. Cumbre de la Sierra de los Cuchumatanes, 28 Dec 1940, Standley 81489 (F); On
high limestone bluff of Caxin, between Tojquia and Caxin bluff, summit of Sierra de los
Cuchumatanes, 3700 m, 6 Aug 1942, Steyermark 50181 (F, MO).

Distribution and ecology. Robinsonecio gerberlfollus is known from alpine and subalpine
pine forests, rocky areas, and meadows w r here it flowers sporadically throughout the year, but with a
peak seemingly between July-December. The species is typified by material from Pico de Orizaba,
the highest mountain in Mexico, and also occurs on Nevado de Toluca (Garcia-Perez 200 1), a very
few other high summits in the Trans Mexican Volcanic Belt, and the Sierra de los Cuchumatanes
range in Guatemala. Although it does not seem to be known in Chiapas (Breedlove 1986), it should
be looked for on Volcan Tacana along the Chiapas-Guatemala border.

Typology. Barkley and Janovec (1996) listed Linden 487 in GH as an isotype. Although
Linden 487 is mechanically the first of three syntypes and the typology of Barkley and Janovec
(1996) indicates basically that they saw authentic material of one of the three syntypes, it nevertheless
seems appropriate to formally designate L inden 487 in K as the lectotype of this name.

Although Robinsonecio gerberlfollus has cypselae that vary from glabrous to pilose (fig. 1F-
G), capitula with l-5(-7) calycular bracts, and the Guatemalan plants are very narrow-leaved, I too
circumscribe R. gerberlfollus broadly and apply this name to material from Guatemala as per the
Jesse Greemnan determination (albeit within "Seneclo sect. Tomentosl Rydb." sensu Greenman 1901,
1902) of Steyermark 501 78 (F, MO) and as treated in the specimens examined section by Barkley and
Janovec (1996).

Excluded species: Senecio cuchumatanensis L.O. Williams & Ait. Molina, Phytoiogla 31:
438. 1975. TYPE: GUATEMALA. Huehuetenango. On high limestone bluff of Caxin, between

Tojquia and Caxin bluff, summit of Sierra de los Cuchumatanes, 3700 m, 6 Aug 1942, Steyermark
501 70 [as "50107"] (holotype: F, photograph in MO; isotype: MO). (Fig. 2).

Seneclo cuchumatanensis was noted by Williams (1975) as resembling R. gerberlfollus,
suggested by Barkley and Janovec (1996) as a possible species of Robinsonecio, and type material of
this name was subsequently annotated by Barkley (en schedula MO) as a species of Robinsonecio.
Although the species is know to me from only two badly bug-damaged collections, its technical
features are intact. This species is shown here as having senecioid microcharacters and is retained in
Seneclo.

Pruski: Robinsonecio microcharacters in Central America 7

Pruski: Robinsonecio

ACKNOWLEDGEMENTS

I thank Craig C. Freeman (KANU), Guy Nesom, and Rosa Ortiz (MO) for reviewing the
manuscript, and Craig for his determinations and helpful discussions. Mike Biomberg (MO),
Stephanie Keil (MO), Fred Keusenkothen (MO), and Rosa Ortiz (MO) kindly prepared the
photograph of the herbarium specimen for publication. Appreciation is extended to Jeremias Lopez
C. (HEM). Francisco (Paco) Lorea H. (XAL), Jorge Martinez M. (HEM), Manuel Martinez M.
(HEM), Nayely Martinez M. (HEM), Ruben Martinez C. (HEM), Rosa Ortiz (MO), and Miguel
Angel Perez F. (HEM), for helping with field work in Mexico.

LITERATURE CITED

Barkley, T.M. 1985. Infrageneric groups in Senecio, s.l., and Cacalia, s.l. (Asteraceae: Senecioneae)

in Mexico and Central America. Brittonia 37: 211-218.
Barkley, T.M, B.L. Clark, and AM. Funston. 1996. The segregate genera of Senecio sensu lato and

Cacalia sensu lato in Mexico and Central America. Pp. 613-620 in D..1.N. Hind et al. (eds.),

Compositae: Systematics. Proceedings of the International Compositae Conference, Kew,

1994, Vol. 1. The Royal Botanic Gardens, Kew.
Barkley, T.M. and J.P. Janovec. 1996. Robinsonecio (Asteraceae: Senecioneae) a new genus from

Mexico and Guatemala. Sida 17: 77-81.
Breedlove, D.E. 1986. Flora de Chiapas. Listados Florist. Mexico 4: v + 1-246.
Dormer, KJ. 1962. The fibrous layer in the anthers of Compositae. New Phytol. 61: 150-153.
Garcia-Perez, J. 2001. Senecio L. Pp. 933-949 in G. Calderon de Rzedowski and J. Rzedowski,

Flora fanerogamica del Valle de Mexico, Ed. 2. Institute de Ecologia, AC, Xalapa, and

Comision Nacional para el Conocimiento y Uso de la Biodiversidad, Patzcuaro, Michoacan.
Greenman, J.M. 1901. Monographie der nord- und centralamerikanischen arten der gattung Senecio.

I. Teil Allgemeines und Morphologie. W. Engelmann, Leipzig.
Greenman, J.M. 1902. Monographie del' nord- und centralamerikanischen arten der gattung Senecio.

Bot. Jahrb. Syst. 32: 1-33.
Hemsley, W.B. 1881. Compositae. Pp. 69-262 in E.D. Godman and O Salvin (eds.), Biologia

Centrali- Americana. Botany, Vol. 2(7-10). Porter, Dulau, & Co, London.
Jeffrey, C. and Y.L. Chen. 1984. Taxonomic studies on tribe Senecioneae (Compositae) of eastern

Asia. Kew Bull. 39: 205^46.
Koyama, H. 1967. Taxonomic studies on the tribe Senecioneae of Eastern Asia. I. General part.

Mem. Coll. Sci. Kyoto Imp. Univ., Ser. B, Biol. 33: 181-209.
Nordenstam, B. 1978. Taxonomic studies in the tribe Senecioneae (Compositae). Opera Bot. 44: 1-

83.
Pippen, R.W. 1968. Mexican "cacalioid" genera allied to Senecio (Compositae). Contr. U.S. Natl.

Herb. 34: 365^47.
Robinson, H. and R.D. Brettell. 1973a. Studies in the Senecioneae (Asteraceae). III. The genus

Psacalium. Phytologia 27: 254-264.
Robinson, H. and RD. Brettell. 1973b. Studies in the Senecioneae (Asteraceae). IV. The genera

Mesadenia, Syneilesis, Miricacalia, Koyamacalia and Sinacalia. Phytologia 27: 265-276.
Wetter, M. A 1983. Micromorphological characters and generic delimitation of some New World

Senecioneae. Brittonia 35: 1-22.
Williams, L.O 1975. Tropical American plants, XVIII. Phytologia 31: 435-447.
Williams, L.O 1976. Flora of Guatemala : tribe VIII. Senecioneae. Fieldiana, Bot. 24(12): 392-423,

585-589.