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Comparative phylogeography of West African amphibians and reptiles
Authors:Adam D Leaché  Jamie R. Oaks  Caleb Ofori-Boateng  Matthew K. Fujita
Affiliation:1. Department of Biology and Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington, 98195;2. Department of Biological Sciences and Museum of Natural History, Auburn University, Auburn, Alabama, 36849;3. CSIR-Forestry Research Institute of Ghana, Kumasi, Ghana;4. Department of Biology, Amphibian and Reptile Diversity Research Center, The University of Texas at Arlington, Arlington, Texas, 76019
Abstract:Comparative phylogeographic studies often support shared divergence times for co-distributed species with similar life histories and habitat specializations. During the late Holocene, West Africa experienced aridification and the turnover of rain forest habitats into savannas. These fragmented rain forests harbor impressive numbers of endemic and threatened species. In this setting, populations of co-distributed rain forest species are expected to have diverged simultaneously, whereas divergence events for species adapted to 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 (frogs) and squamates (lizards and snakes) that are distributed across the Dahomey Gap, a climate change-induced savanna barrier responsible for fragmenting previously contiguous rain forests of Ghana into two regions: the Togo-Volta Hills and the Southwestern Forests. A model of asynchronous diversification is supported for anurans and squamates, suggesting that drivers of diversification are not specifically related to ecological and life history associations with habitat types. Instead, the wide variability of genetic divergence histories exhibited by these species suggests that biodiversity in this region has been shaped by diversification events that extend beyond the Holocene. Comparisons of the genealogical divergence index, a measure of the genetic divergence between populations due to the combined effects of genetic isolation and gene flow, illustrate that these populations represent a broad sampling of the speciation continuum.
Keywords:Comparative phylogeography  Dahomey Gap  diversification  genealogical divergence index  West Africa
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