Species formation and geographical range evolution in a genus of Central American cloud forest salamanders (Dendrotriton)

Aim Montane Central America offers an ideal system for testing geographical hypotheses of species diversification. We examined how the complex geological history of Nuclear Central America has shaped the diversification of a genus of cloud-forest-inhabiting salamanders (Dendrotriton). We applied parametric models of geographical range evolution to determine the predominant mode of species formation within the genus and to test existing hypotheses of geographical species formation in the region. Location Montane cloud forests of Nuclear Central America. Methods We estimated a species tree for Dendrotriton using a multi-locus DNA sequence data set and several coalescent methods, and performed molecular dating for divergence events within the genus. We then applied the species-tree estimate to a likelihood-based time-stratified model of geographical range evolution, based on current species distributions and available geological information for Central America. Results Species trees from all methods contain two groups, one corresponding to species from the Sierra de los Cuchumatanes and the other containing all remaining species. In most cases, species formation within the genus involved an even division of the geographical range of the ancestral species between descendant species. The ancestor of extant Dendrotriton species was estimated to have occurred in either the Sierra de los Cuchumatanes or the Sierra Madre de Chiapas, and both of these areas appear to have been important for diversification within the genus. The single species found in the Quaternary-age Guatemalan volcanic cordillera dispersed to the volcanoes from an older highland area. Main conclusions Models of geographical range evolution, when combined with robust species-tree estimates, provide insight into the historical biogeography of taxa not available from phylogenies or distributional data alone. Vicariant species formation, rather than peripatric or gradient speciation, appears to have been the dominant process of diversification, with most divergence events occurring within or between ancient highland areas. The apparent dispersal of Dendrotriton to the Quaternary-age volcanoes raises the possibility that the rich salamander community there is composed of species that dispersed from geologically older areas. The Motagua Valley appears not to have been as important in vicariant species formation within Dendrotriton as it is within other groups.