Comparative phylogeography of West African amphibians and reptiles

Comparative phylogeography often supports shared divergence times for co-distributed species with similar life history traits and habitat specializations. Since the Last Interglacial, West Africa has experienced gradual aridification and the turnover of rainforest habitats into savannas. Today, the remaining rainforest fragments harbor impressive numbers of endemic and threatened species. In this setting, populations of co-distributed rainforest restricted species are expected to have diverged simultaneously, whereas divergence events for species in savanna and forest-edge habitats should be absent or idiosyncratic. We conducted a Bayesian analysis of shared evolutionary events to test models of population divergence for 20 species of anurans and squamates that are distributed across the Dahomey Gap, a dry savannah corridor responsible for fragmenting the previously contiguous rainforests of Ghana into two regions: the Togo-Volta Hills and the Southwestern Forests. A model of asynchronous diversification is supported for anurans and squamates in both environments, suggesting that drivers of diversification are not specifically related to ecology and life history.