Estudos filogenéticos em desmodium desv. (Leguminosae-Papilionoideae) e revisão taxonômica das espécies ocorrentes no Brasil

Abstract

Desmodium includes about 275 species, has almost cosmopolitan distribution and diversity centers in Mexico and South America. This study presents studies on phylogeny of the genus in South America and a taxonomic revision of the Brazilian species. The phylogenetic study was carried out by 80 sequences of the nuclear ribossomal region (ITS) using Maximum Parcimony, Maximum Likelihood and Bayesian Inferences. The genus Desmdium as widely circumscribed, including Old World taxa, was inferred as polyphyletic, but the New World taxa formed two supported clades: (1) one grouping weedy pantropical species probably from Asia but with one species from the Amazon, and (2) an American clade comprising a Meso-American grade which includes a temperate North-American clade and a South-American clade mostly from tropical and temperate fields (Cerrado and Pampa). Diversification analysis supported a recent age for the American clade (mean crown age = 3.99Ma) and most speciation along the last 2.5Ma. The taxonomic revision was based on the analysis of about 3,000 specimens from 77 herbaria and botanical material of fieldwork. This study resulted in the recognition of 34 species, and Desmodium album (Schindl.) J.F. Macbr. as a new occurrence in Brazil. Three species were collected for the first time after the type collection. We proposed 60 lectotypes, two neotypes, 27 new synonyms, one new name and one new combination. Descriptions, identification key, illustrations, distribution maps, taxonomic and nomenclatural comments for all species are presented. One new specie was described for Argentina.