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

古代湖泊是生物多样性的主要来源，也是特有物种的热点。它们的年龄(&gt；10万年)非常适合研究过去的殖民史和湖内多样化/物种形成的过程。影响物种形成的主要因素可以是外在的，也可以是内在的，而且确实经常相互作用。推动生物多样性产生的最重要的外部因素是主要的地质、湖泊或气候变化以及相关的湖泊水位波动。然而，研究外在和内在因素对多样化速率的影响需要对各自湖泊系统的地质和气候历史有充分的了解。它进一步保证了合适的模型系统，最好是完整的分子系统发育加上统计方法，允许估计从时间校准的分子系统发育的多样化速率。这项建议的主要目标是通过对七个主要古代湖泊进行荟萃分析，在广泛的时空尺度上识别驱动从中新世到晚更新世的古湖腹足类物种形成过程的主要外部因素。荟萃分析包括生成分子系统发展图、经过时间校准的系统发展图、多样化比率分析和平衡分析(确定湖泊的承载能力)，以及将环境变化与多样化/物种形成联系起来。这些分析主要基于已发表的DNA序列，但也伴随着在该项目过程中获得的其他序列。在不同的分类类群之间进行这种荟萃分析，可以比较同一环境(湖泊)中不同类群之间的多样性比率，以及居住在不同湖泊系统中的相同类群(属、科)之间的多样性比率。本建议通过结合项目过程中获得的演化、地质和环境数据以及已发表的研究成果，为古湖泊研究提供了一种新的跨学科方法。这是在全球范围内比较框架内研究古湖泊多样性格局的首次尝试。这个项目的结果将提供对几个腹足类物种形成的模式和速度的洞察，以及潜在外部因素对多样性的影响，并可能成为进一步对其他无脊椎动物和脊椎动物群体进行荟萃分析的基础。利用所有目标群体的时间校准的系统发育来推断主要进化(物种形成)事件的时间框架，将有助于进一步了解其中一些湖泊的不确定和不连续的湖沼学历史。此外，由于许多湖泊中缺乏(较老的)化石，利用最近分类群的分子(DNA)数据与基于外部速率的时间校准树(或如果有化石校准)相结合的方法可能会引起古生物学家和地质学家的极大兴趣。

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.