A NEW SPECIES OF
TRIGONOSPERMUM
(COMPOSITAE,
HELIANTHEAE) FROM
CENTRAL AMERICA
In preparing treatments of Compositae for the
Flora de Nicaragua project, an unusual specimen
was discovered in the genus Trigonospermum that
could not be placed with existing revisionary lit-
erature (McVaugh & Laskowski, 1972; Turner,
1978). Examination of material of the genus from
other institutions revealed additional specimens and
led us to treat these as a new taxon at the specific
level.
Trigonospermum stevensii Sundberg et Stues-
sy, sp. nov. TYPE: Nicaragua. Depto. Madriz:
Cerro Quisuca, lower S and SW slopes, ca.
13�30'N, 86�31'W, 800 1,100 m, dry forest
on rocky slopes, 23 Nov. 1979, W. D. Stevens
& A. Grijalva 16156 (holotype, OS; isotypes,
MO, OS, OSH). Figure 1.
A 7: annuo McVaugh & Laskowski et T. melampo-
dioide DC. simile, sed paleis exteriores glabris, apice
ciliatis, floribus radii 3-4, ramis styli 0.9-1.4 mm longis,
ligulis 4.5-7 mm longis, achaeniis 2.5-3.2 mm longis,
floribus disci 18-25, lobis corollae sparsim pubescentibus
vel glabris, antheris 1.1-1.3 mm longis.
Annual herb, ca. 1 m tall. Stems hispidulous,
stalked-glandular. Leaves opposite; blades rhom-
bic-ovate, 5-15.5 cm long and 3-11 cm wide,
hispidulous and occasionally glandular above, stri-
gose and glandular below, acute at the apex, with
margin serrulate; petiole winged, to 5.5 mm long.
Peduncle slender, hispid, stalked-glandular. Capitu-
la numerous; involucre 2.8-4 mm tall; outer phyl-
laries linear-elliptic, 2.4-4 mm long, 0.8-1.6 mm
wide, hirtellous, glandular, grading into middle
phyllaries; middle phyllaries rhombic to obovate,
slightly keeled, 2.2-3.2 mm long, apex acute to
apiculate, fimbriate-ciliate; inner phyllaries wrap-
ping around achenes, obovate, scarious, white, 2.2-
3 mm long, 10-nerved, glabrous except at the
rounded, fimbriate-ciliate apex. Ray florets 3-4;
corollas yellow; ligules 4.5-7 mm long, 3-6 mm
wide, gland-dotted both sides, deeply trilobed, with
lobes rounded, 2-4 mm long; tube pubescent, 0.3-
0.5 mm long; style branches 0.5-1.4 mm long;
achenes broadly elliptic to obovate, sometimes 3-
angled, broadest above the middle, 2.5-3.2 mm
long, with terminal scar elevated 0.2 mm. Disk
florets 18-25, with abortive ovaries; corollas 2.1-
2.7 mm long; lobes 5, 0.1-0.3 mm long, glabrous
to sparsely pubescent; styles fused (not bifid); an-
thers 1.1-1.3 mm long, exserted half their length
at anthesis. Pales filiform-subulate to oblanceolate,
fimbriate at apex, 1.8-2.6 mm long.
Additional specimens examined. GUATEMALA. DEPTO.
CHIMALTENANGO: Chimaltenango Experimental Station,
2,000 m, 5 Nov. 1971, A. Molina R. & A. R. Molina
26919 (MICH); DEPT. HUEHUETENANGO: ca. 5 mi. WNW
of Huehuetenango, 23 Oct. 1976, T F. Stuessy & R.
C. Gardner 4318 (TEX); DEPT. SACATEP�QUIIEZ: slopes of
Volcan de Agua, S of Santa Maria de Jesus, 1,800-2,100
m, 10 Dec. 1938, P.C. Standley 59378 (MICH).
This new taxon is morphologically intermediate
between Trigonospermum annuum McVaugh &
Laskowski and T. melampodioides DC. (Table 1).
Most importantly, it differs from T. annuum in ray
corolla length, disk floret number, anther length,
and achene length. It differs from T. melampo-
dioides in pubescence of lobes of the disk corollas
and outer pales.
The morphologically intermediate nature of T.
stevensii could be due to interspecific hybridization,
but two observations argue against this. First, pol-
len stainability of the specimens is high (99% of
500 grains in cotton-blue in lactophenol), and the
pollen grains appear normal. Second, the possible
parents, T. melampodioides and T. annuum, occur
in Mexico reaching only as far south as Oaxaca,
and therefore do not occur within the range of T.
stevensii. This new species, in fact, is allopatric to
ail other taxa in the genus. These considerations
further suggest specific recognition for 7: stevensii.
Additional fieldwork could alter this viewpoint, how-
ever, as well as concepts of other poorly collected
taxa in the rest of the genus (e.g., T. auriculatum
Turner).
The discovery of Trigonospermum stevensii in
Nicaragua extends the range of the genus south-
ward into Central America, previously known only
from Mexico and Guatemala. The new species is
named in honor of Dr. Warren Douglas Stevens,
ANN. MISSOURI BOT. GARD. 77: 418-420. 1990.


Volume 77, Number 2
1990
Notes
419
1mm
Imm
1mm
FIGURE 1. Trigonospermum stevensii, showing habit, capitulum (with facing ray floret removed), and outer
phyllary and achene (same scale). All Stevens & Grijalva 16156 (holotype).
who is coordinating the Flora de Nicaragua proj- when this paper was written; NSF Grant INT-
ect. 8402888 for support of manuscript preparation;
MICH and TEX for loan of specimens; curators
Thanks are expressed to The Ohio State Uni- of GH, MO, NY, and TEX for courtesy during
versity Graduate School for a University Postdoc- visits; B. L. Turner for critical comments on the
toral Fellowship to the senior author 1986-1987, manuscript; and James Zech for drawing Figure 1.


Annals of the
Missouri Botanical Garden
TABLE 1. Comparison of Trigonospermum stevensii with T. annuum and T. melampodioides.
Character 7� annuum T. stevensii T. melampodioides
Duration annual annual perennial
Inner phyllary
Vestiture glabrous glabrous strigose
Margin apically ciliate apically fimbriate-ciliate apically erose
Ray floret
Number 3-4 3-4 (4-)5(-10)
Style branch length (mm) 0.4 1 0.5-1.4 0.9-1.5
Ligule length (mm) 1.5 3.5 4.5-7 5-8.4
Achene length (mm) 2.8-3.8 2.5-3.2 1.8-3
Disk floret
Number 8-13 18-25 19-50
Corolla lobe vestiture sparsely pubescent sparsely pubescent or glabrous densely pubescent
Anther length (mm) 0.5 1 1.1-1.3 0.8-1.3
LITERATURE CITED
McVAiUH, R. & C. W. LASKOWSKI. 1972. The genus
Trigonospermum Less. (Compositae, Heliantheae).
Contr. Univ. Michigan Herb. 9: 495-506.
TURNER, B. L. 1978. New species and combinations in
the genera Sigesbeckia and Trigonospermum (Com-
positae: Melampodiinae). Brittonia 30: 64-68.
-Scott D. Sundberg and Tod F. Stuessy, De-
partment of Botany, The Ohio State University,
Columbus, Ohio 43210, U.S.A. (Present address
of senior author: Department ofBotany, Univer-
sity of Washington, Seattle, Washington 98195,
U.S.A.)
420