Revision of Viguiera sect. Maculatae (Asteraceae: Heliantheae)

Abstract

Revision of Viguiera sect. Maculatae (formerly series Maculatae) results in recognition of 14 taxa, including 13 species and one subspecies. Of these, V. guerrerana, V. mirandae, V. sharpii, V. splendens, and V. eriophora subsp. poblana are newly described. All taxa are endemic to Mexico; distribution maps and illustrations are presented for each. Cladistic analysis, based on morphological characters, was used to explore possible phyletic relationships among taxa, and led to the division of the section into two series. Series Adenophyllae is characterized by subcylindric or campanulate heads and oblong pales; series Maculatae has campanulate to hemispheric heads and ovate pales. Chromosome numbers determined for ten of the taxa are uniformly n = 17, suggesting that, for the section, this is the base number and that polyploidy does not occur. Viguiera Kunth comprises approximately 180 species distributed from the western United States to central Argentina, with major concen- trations of species occurring in the central An- des, in south-central Brazil, and in south-central Mexico. The genus occurs primarily in season- ally dry, arid, elevated areas with some of its members extending into tropical lowlands. The genus includes herbaceous annuals and peren- nials as well as shrubs and small trees. Viguiera was established by Kunth (1820) based on the Cuban Viguiera helianthoides Kunth (later synonymized under Viguiera dentata (Cav.) Sprengel). The generic name honors French physician L. G. A. Viguier. According to Kunth, the genus is distinguishable from Helianthus L. by its receptacle, involucre, and pappus. Later authors (Cassini 1821; Gardner 1848; Bentham 1873) relied more heavily on the nature of the pappus of Viguiera (persistent with two awns and several squamellae in between) to separate it from Helianthus (pappus of deciduous awns with few or no squamellae). The species discussed in this paper were placed by Blake (1918) in subg. Viguiera (Cal- anticaria S. F. Blake) of sect. Viguiera (sect. Chlor- acra S. F. Blake) series Maculatae. More than half of the Mexican species of Viguiera are classified within this section. Blake (1918) relied heavily on morphological features of the phyllaries, which in sect. Viguiera are ovate-oblong, and indurated at the base with a narrow herbaceous apex. He distinguished series Brevifoliae, Den- tatae, Grammatoglossae, Maculatae, and Pinnati- lobatae by differences in the proportion and shape of the herbaceous and indurated parts of the phyllary. Blake also mentioned several oth- er distinguishing features such as habit, pappus, and head size, which supplemented the phyl- lary differences he observed. Seven species were included by Blake (1918) in series Maculatae: V. adenophylla, V. eriophora, V. maculata, V. oaxacana, V. quinqueradiata, V. sphaerocephala, and V. tra- chyphylla. According to Blake (1918), these species shared a perennial habit; scabrous, ovate leaves; oblong or oblong-lanceolate phyllaries with an indurated and vittate pale-margined base and a triangular herbaceous apex; and in- volucres arranged in 2-3 series. Since Blake's treatment, three new species be- lieved to be closely related to series Maculatae have been discovered. Miranda (1943) suggest- ed that V. insignis be placed in series Maculatae, probably based on the shrubby or tree-like hab- it of the species, although the pappus and num- ber of series of phyllaries (six to seven) present in this species do not conform to the series. Another species with apparent affinities to se- ries Maculatae but not conforming to its features is V. puruana, which has achenes with well-de- veloped awns but highly reduced squamellae. However, this species appears to be closely re- lated to two species of series Maculatae, V. oaxa- cana and V. sphaerocephala, with which it shares similar pale and phyllary structures. The third species, V. neocronquistii, conforms to the basic characters of the series. The present account is based on field work combined with laboratory and herbarium stud- ies of morphology, chemistry, and chromosome numbers. These studies suggest that the group is sufficiently distinctive to warrant sectional