Diversity and phylogeography of anurans of the highlands of Ethiopia.
详细信息
文摘
Located in Eastern Africa, Ethiopia is a country of unique geological features, among them the largest continuous Afro-alpine zone in Africa and the Great Rift Valley GRV). The GRV formation began ~20 mya； it is a fault system that splits the central Ethiopian dome in two separate highland systems Baker et al., 1972, Chorowicz, 2005). In spite of the general assumption that the GRV has played a major role in shaping the biodiversity of the country, its influence has not been fully investigated, as only a handful of studies have addressed its impact on the phylogeographic and evolutionary history of Ethiopian taxa Assefa et al., 2007； Belay and Mori, 2006； Ehrich et al., 2007； Gotelli et al., 2004； Kebede et al., 2007； Lehmann et al., 2000； Ramdhani et al., 2008； Wieczorek et al., 2000). For my research I decided to investigate if and how the GRV and Plio-Pleistocene climatic oscillations have impacted the distribution and genetic structure of taxa of the highlands of Ethiopia. I had three goals: 1) to assess the distribution and genetic structure of species from the Ethiopian highlands； 2) to infer the role of the GRV on the evolutionary history of highland organisms； 3) to investigate the impact Pleistocene cyclic glaciation events have had on the environment of the rift valley and how they have determined the persistence of the GRV as a vicariant barrier. For my research I chose to use anurans because of their dispersal limitations and because it is one of the most diverse, yet least studied, vertebrate groups in Ethiopia. Since anurans are poor dispersers, they retain the signature of past demographic and biogeographic events better than organisms with high dispersal abilities e.g. large mammals). For this reason, anurans have been widely used to study dispersal, speciation, biogeography and the origin of endemism Measy et al., 2007, Vences et al., 2003, Vences et al., 2005, Wiens, 2007). The first chapter of this dissertation is an introduction where I give background information on the study area, Ethiopia. In the second chapter I address the phylogeny and evolution of frogs of the genus Ptychadena Boulenger 1917) in the highlands of the country. The third chapter deals with the phylogeography of four Ptychadena species and examine the role the GRV and the Plio-Pleistocene climatic oscillation have had on their evolution and present distribution. The fourth chapter is a comparative phylogeography of three Ethiopian anurans, with very different ecology: Amietia angolensis Bocage 1866), Leptopelis gramineus Boulenger 1898) and Tomopterna kachowskii Nikolskii 1900).