Colonization and diversification dynamics in ancient lake species flocks inferred from meta-analyses on freshwater gastropods

点击翻译按钮获取中文摘要

Ancient lakes are key sources of biodiversity and hotspots of endemism. Their age (>100,000 years) suite them well for studying past colonization histories and processes of intra-lacustrine diversification/speciation. Main factors affecting speciation can be extrinsic or intrinsic and do often interact. The most important extrinsic factors driving the generation of biodiversity are major geological, limnological or climatic changes and related lake-level fluctuations. However, studying the impact of extrinsic and intrinsic factors on rates of diversification requires a well-understood geological and climatic history of the respective lake system. It further warrants suitable model systems and preferably complete molecular phylogenies plus statistical methods that allow to estimate diversification rates from time-calibrated molecular phylogenies.The main goal of this proposal is to identify main extrinsic factors driving speciation processes in ancient lake gastropods from the Miocene to the late Pleistocene on a broad spatiotemporal scale by performing a meta-analysis across seven major ancient lakes. Meta-analyses include generating molecular phylogenies, time-calibrated phylogenies, diversification-rate analyses and equilibrium analyses (identifying the carrying capacity of the lake), and linking environmental changes and diversification/speciation. These analyses are mainly based on published DNA sequences, but are also accompanied by additional sequences obtained in the course of this project. Performing such meta-analyses among different taxonomic groups allows for the comparison of diversification rates among different groups in the same environment (lake) and among the same groups (genera, families) inhabiting different lake systems.The present proposal provides a novel interdisciplinary approach for ancient lake studies by combining evolutionary, geological and environmental data obtained during the course of the project and from published studies. It is the first attempt to study diversification patterns in ancient lakes in a comparative framework on a global scale. Results obtained from this project will provide insights into modes and tempo of speciation in several gastropod groups and the impact of potential extrinsic factors on diversification and may form the basis for further meta-analyses in other invertebrate and vertebrate groups.Inferring the timeframe of major evolutionary (speciation) events by using time-calibrated phylogenies for all target groups will further help understanding the uncertain and discontinuous limnological history of some of these lakes. Moreover, because of the lack of (older) fossils in many lakes, the approach of using molecular (DNA) data of recent taxa in a combination with time-calibrated trees based on external rates (or fossil calibration if available) may be of great interest for both palaeontologists and geologists.