A molecular phylogeny of the genus diplusodon (Lythraceae), endemic to the campos rupestres and cerrados of South America

Abstract

Diplusodon is the second-largest genus of the Lythraceae with 103 species of shrubs or subshrubs endemic to the Cerrado Domain. Many species are narrow endemics, restricted to campos rupestres on quartzite rocks, while others are found in cerrado and, more rarely, in gallery, or dry forest margins. Phylogenetic relationships inferred from nuclear ITS and ETS sequences strongly support the monophyly of Diplusodon. We found four major clades, three of which are strongly correlated with endemism and are centered in the Espinhaço Range (CEP), the Plateau Goiano (PG) and the Chapada Diamantina (CD). The fourth clade was designated the Cerrado clade (C), containing species from all three centers of diversity as well as widely distributed species and several species of lower-elevation cerrado. Species with the most plesiomorphic features occur in the clades east of the São Francisco River (C, CEP, CD), while the greatest morphological diversity is found in the PG. The crown node of the genus is estimated to date to the late Pliocene, likely diversifying in the campos rupestres, where most of the later Pleistocene speciation bursts also appear to have occurred. These patterns of diversification in Diplusodon appear to agree with old stable landscapes (OSL) theory, where high levels of in situ speciation in islands of campo rupestre, possibly isolated by more intense fire regimes of the surrounding cerrado vegetation, resulted in accumulation of high numbers of microendemic species. However, the adaptability of the genus is evidenced by multiple dispersal events to lower elevation cerrado, several long-distance dispersals, notably in the C clade, and the presence, in several clades, of species found both in campo rupestre and cerrado habitats.