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Abigail
Moore
Research Training Program, 2003
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The Delimitation of Viguiera pazensis and V. procumbens (Asteraceae) Abstract The
genus Viguiera is a member of the sunflower family (Asteraceae).
It has been credited with more than 150 species native to the New World.
Two of these species are V. pazensis and V. procumbens,
both native to the Andes. S. F. Blake, in his 1918 monograph of Viguiera,
claimed they were distinct species and gave characters for distinguishing
between them. We tested Blake’s hypothesis by examining herbarium
specimens of the both species to determine if they represent two species
or one variable species. It was concluded that they represent the same
species because no characters could be found to distinguish them. Individuals
of both species will now be classified under the older name V. procumbens.
The
genus Viguiera Kunth in H.B.K. is a member of the sunflower family.
Its species are native to the New World, primarily Central and South
America. The last complete study of the genus, by S. F. Blake in 1918,
included 143 recognized species. However, recent work has shown that
many species in the traditional Viguiera are more closely related
to other plants, such as the sunflower itself (Helianthus L.),
than they are to other Viguiera species (e.g., Schilling and
Jansen, 1989; Schilling and Panero, 2002). Therefore, Viguiera
is being broken up into several smaller, natural genera whose species
are each other’s closest relatives. The species in this study will
ultimately be removed from Viguiera and placed in the genus Rhysolepis
S.F.Blake.
The
sunflower family includes many familiar plants such as lettuce, dandelions,
daisies, thistles, ragweed, and sagebrush. These plants share the characteristic
of having flowers aggregated into heads. The sunflower family is one
of the largest families of plants, with over 20,000 species.
Viguiera pazensis Rusby and V. procumbens (Pers.) S.F.Blake are both native to the Andes of Bolivia and Peru. Viguiera pazensis was described in 1893 from specimens collected near La Paz, Bolivia. Viguiera procumbens was described in 1807 from specimens collected somewhere in Peru. The locality information on specimens collected that long ago is not very precise. Besides
V. pazensis and V. procumbens, several other names were
applied to this group of plants: V. pflanzii Perkins and V.
calva (Sch. Bip.) Britton. Scientists from several different countries
were naming these plants all at the same time and it was easy to get
multiple names for the same species. In addition, people working on
Bolivian plants might not always look through the Peruvian names to
determine if they were about to describe something that already had
a name in Peru.
We
examined the specimens of each species in the collection of the National
Herbarium using dissecting microscopes. In total, approximately 170
specimens were examined. We also examined the flowers of four individuals
using a compound microscope to check for differences in small floral
characters. A number of different characters were examined including
leaf shape and size; types of hairs on the leaves and stems; bract shape,
size, and hairs; pappus structure; and flower structure.
No consistent differences were found between most plants placed in Viguiera pazensis including the type of the species and plants placed in V. procumbens. Some characteristics, such as leaf shape and size and degree of reflexing of the tips of the involucral bracts, varied among the specimens, but variation in one character did not correlate with variation in any of the others. It was concluded that such variation was not significant. Viguiera pazensis was therefore synonymized with V. procumbens, because procumbens is the older name. We also attempted to find characters that would define the new V. procumbens.
The
authors would like to thank V. A. Funk for valuable discussion and M.
Knowles for technical assistance. AJM was supported by the National
Science Foundation Research Experiences for Undergraduates program Award
Number DBI-0243512. References Cited Blake, S. F. 1918. A revision of the genus Viguiera. Contrib. Gray Herb. 54: 1-205. Schilling, E. E. and R. K. Jansen. 1989. Restriction fragment analysis of chloroplast DNA and the systematics of Viguiera and related genera (Asteraceae: Heliantheae). Amer. J. Bot. 76: 1769-1778. Schilling,
E. E. and J. L. Panero. 2002. A revised classification of subtribe Helianthinae
(Asteraceae: Helinatheae): I. Basal lineages. J. Linn. Soc., Bot. 140:
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