Phylogenetic relationships of the Mexican tussilaginioids (Asteraceae). Phylogeny of Mexican tussilaginioids

The Mexican tussilaginioid clade (Asteraceae: Senecioneae) consists of 13 genera distributed from the USA to Panama, with most species occurring in montane regions from Central Mexico to Guatemala. Presently, 141 species are recognized in this clade, with many considered to be endemic to threatened pine-oak or cloud forest ecosystems. We conducted a phylogenetic investigation of the Mexican tussilaginioid clade, using nuclear ribosomal DNA sequences of 62 species from 12 different genera. The results of our analyses strongly support the monophyly of the Mexican tussilaginioid group. Topology-based hypothesis testing using constraint models indicated that the genera Pittocaulon, Psacaliopsis and Roldana may not be monophyletic. The genus Telanthophora was found monophyletic, but nested within Roldana. Endemism is abundant among the clades identified, with over half of the species restricted to relatively small geographic areas. Moreover, most members of the Mexican tussilaginioids inhabit montane regions at or above 1500 m in Mexico and Guatemala and are thus under immense pressure from human land use.