Demographical expansion of Handroanthus ochraceus in the Cerrado during the Quaternary: implications for the genetic diversity of Neotropical trees

Abstract

Phylogeographical studies provide insights into the dispersal dynamics of species needed to understand the effects of Quaternary climate changes on the spatial patterns of genetic diversity. We used a multi-model inference approach coupling ecological niche modelling (ENM) with a relaxed random walk model to reconstruct the spatio-temporal history of lineage dispersal of the Neotropical tree species Handroanthus ochraceus. We sampled 24 populations throughout the Cerrado Biome and analysed polymorphisms at three intergenic chloroplast regions and ITS. Coalescent analyses revealed demographical expansion since c. 380 ka. Although ENM predicted no range expansion, coalescent simulations reinforce the pattern of range expansion because demographical expansion was the most likely scenario able to produce the observed spatial pattern of genetic diversity of H. ochraceus. Its most recent common ancestor dated from ~1.9 Ma, and lineages cyclically dispersed from the Southeast and West towards Central–West Brazil. Most dispersal events occurred from populations at the edges of the Cerrado towards Central Brazil. Populations at the edge of the historical refugium show higher genetic diversity and were the source of migrants to central populations. A wide historical climatic refugium through time for H. ochraceus may have allowed dispersal of lineages among populations of Central Brazil, maintaining their historical connectivity and genetic diversity.