Taxonomic Revision and Morphometric Analysis of Gamochaeta (Asteraceae, Gnaphalieae)

Susana E. Freire; Mariana A. Grossi; Néstor D. Bayón; Claudia Monti; Laura Iharlegui; María A. Migoya

doi:10.3417/2024836

Susana E. Freire Museo Argentino de Ciencias Naturales (MACN-CONICET)
Mariana A. Grossi Museo de La Plata
Néstor D. Bayón Universidad Nacional de La Plata
Claudia Monti Universidad Nacional de La Plata
Laura Iharlegui Museo de La Plata
María A. Migoya Universidad Nacional de La Plata

DOI: https://doi.org/10.3417/2024836

Keywords: Cluster analysis/unweighted pair group method with arithmetic mean dendrogram, Compositae, morphology, New World, phenetics, synonyms, taxonomy

Abstract

Gamochaeta Wedd. (Asteraceae, Gnaphalieae) is a New World genus with a center of diversity in South America. The genus is characterized by capitula usually arranged in spikes or headlike clusters; pistillate florets outnumbering the bisexual florets; truncate style branches with apical sweeping trichomes; pappus bristles connate at the base into a ring that falls as a unit; and achenes with usually globose twin trichomes. We present here the first morphometric analysis of this genus. Based upon these results, 53 species are recognized, and two are newly synonymized: G. neuquensis Cabrera under the name G. chamissonis (DC.) Cabrera, and G. impatiens G. L. Nesom under the name G. americana (Mill.) Wedd. A lectotype is newly designated for Gnaphalium spiciforme Sch. Bip. The occurrence in southern Argentina of Gamochaeta procumbens (Phil.) Cabrera is reported for the first time, and G. standleyi (Steyerm.) G. L. Nesom is new for Colombia. One species, Gamochaeta thouarsii (Spreng.) Anderb., is treated as dubious. A key to the species is provided, as well as morphological descriptions, synonymy, distribution and habitat information, distinguishing characters, taxonomic affinities, distribution maps, illustrations of the species, and additional material examined.