Nuclear and chloroplast DNA phylogeography of Ficus hirta: obligate pollination mutualism and constraints on range expansion in response to climate change

Abstract

This study uses a phylogeographic approach to investigate how interspecific interactions in an obligate pollination mutualism enhance or constrain dispersal and the range distributions of species through time. Fifteen populations of Ficus hirta, a bird-dispersed fig pollinated by a species-specific fig wasp, were sampled from Thailand to the northern limits of the tropical forest in China. These populations were assayed for six nuclear microsatellite loci and two intergenic chloroplast DNA sequences. Analyses of range expansion and genetic clustering indicated a relatively slow rate of range expansion from two or more southern glacial refugia. Low nuclear differentiation, combined with high interpopulation differentiation, and phylogeographic structuring of chloroplast variation indicated that seed dispersal has had a greater constraint than obligate interactions with fig wasps on the rate of post-glacial range expansion. This study is the first to investigate the phylogeographic history of a widely distributed southeast Asian tropical plant whose distribution extends to the northern limits of tropical forest habitat in China. It is also the first study of Ficus utilizing molecular data to evaluate whether species-specific pollination is a limitation or an aid to range expansion in response to climate change.