Résumé
Abstract
We investigated spatial genetic structuring in two vicariant Ficus spp. (F. insipida and F. adhatodifolia), occurring in the Amazon Forest and the Atlantic Forest, respectively. We explain this structuring in a phylogeographical framework of variation in the extent and location of favourable habitats for the two species during climatic oscillations. Plastid (trnH-psbA, trnS-trnG) and nuclear (ITS) regions were sequenced and species distribution models were used to explore the expected variation in the species ranges and to relate this variation to the patterns of genetic diversity. Both species presented higher population differentiation in plastid than in the nuclear markers. Despite the presence of a large number of plastid DNA haplotypes, most populations of F. insipida had only one haplotype. Distribution modelling results indicated no drastic change in the distribution of F. insipida during the Pleistocene. In contrast, F. adhatodifolia exhibited low diversity of nuclear and plastid haplotypes with four exclusive haplotypes for plastid DNA and a highly divergent one, shared with F. insipida, in the central region of South America. Distribution modelling showed a drastic change in the range of F. adhatodifolia during the Last Glacial Maximum (LGM), which may explain the reduced diversity in this species compared to F. insipida. During the LGM, the distribution of F. adhatodifolia became disjunct, with a region of somewhat favourable climate inland, corresponding to the populations presenting the plastid DNA haplotype shared with F. insipida, whereas the coastal regions of favourable climate were displaced northwards. This result suggests that inland populations of F. adhatodifolia were somewhat introgressed by F. insipida during that period. Our results suggest major differences in the history of Amazonian and Atlantic Forest as seen through the prism of two pioneer trees that are associated with wetter areas and dense vegetation.