Among cradles and museums: seasonally dry forest promotes lineage exchanges between rain forest and savanna

Background: Cerrado comprises heterogeneous vegetation types. The flora of the vegetation types has distinct biogeographic origins and thus can be hypothesised to have distinct evolutionary imprints. Aims: We hypothesised that the flora of riparian forest was phylogenetically overdispersed, whereas those of more open habitats were phylogenetically clustered. Methods: We built a species-level phylogeny for 1,663 species of trees, shrubs and palms and analysed the pattern of lineage distribution, alpha and beta phylogenetic diversity among Cerrado vegetation types (riparian forest, rocky savana, savana and seasonally dry forest - SDTF). Results: We found a gradient of high phylogenetic diversity and overdispersion from riparian forests towards phylogenetic clustering in vegetation in more open and drier habitats. Habitat shifts were common along the evolutionary history of all families analysed and most families showed a high frequency of shifts from SDTF to riparian forest and savanna. Conclusions: SDTF seems to be a transitional habitat in evolutionary terms, promoting lineage exchanges between stands of riparian forest and savanna. While riparian forest can be seen as a ‘museum’, that harbours ancient lineages, savanna and rocky savanna are a ‘cradle’ of derived lineages. Habitat shifts are an important underlying drive of high present-day Cerrado flora diversity.