Freshwater gastropods in the Neogene and Quaternary of Europe

This study will provide the first detailed assessment of the composition of European freshwater gastropods during the Neogene and Quaternary at species, genus and family levels, with emphasis on lake faunas. Biodiversity and composition of Holocene lake faunas seem to be strongly influenced by the Quaternary Ice Ages. Several short- lived Miocene lakes, however, are strikingly "modern" in their generic inventory and genus/species relations, suggesting that the modern composition is not necessarily a young pattern, explained only by the glacial bottleneck. In contrast, the modern long-lived lakes of Europe host gastropod assemblages with high endemicity and striking similarities with pre-Pleistocene lake faunas. The origin of these modern faunas, however, is still enigmatic. In a first step, the -diversity of several hundred modern and fossil European lakes will be evaluated. An international expert team of palaeontologists and limnologists, with long-lasting experience with the fossil and modern faunas, European stratigraphy, and a deep knowledge on the exhaustive relevant literature, is available for data acquisition, evaluation and controlling. In the next step the huge accumulation of data will be made available permanently for the public via the FreshGEN-database (Freshwater Gastropods of the European Neogene). This database will be set up to meet current standards for management and storing of electronic biodiversity data and will be compatible with related projects. The most important topics to be tackled based on the data, are to search for factors, which explain the -diversities through time and to look for geographic gradients in species richness and/or faunal composition. Diversity data and inter-lake comparison will allow estimating endemism rates and quantitatively defining biodiversity hotspots in present and past lakes. Shells-sizes of all taxa will be evaluated to search for general patterns and to define phases of conspicuous "gigantism". The well resolved climate history of Europe during the last 23 million years will be a frame for linking species- and supraspecific compositions with climatic trends and events. Ideally, the project will shed light on the origin of modern lake faunas by the intense cooperation between zoologists and palaeontologists. A major aim is to map and define a statistics-based Pan-European biogeography and palaeobiogeography of Neogene to Quaternary freshwater systems. Once established, this database will be open for geographic and/or stratigraphic expansion. Finally, the data are a solid base to estimate the (future) anthropogenic impact on Holocene lake faunas.

The FreshGEN-project presents the first detailed assessment of the composition of European freshwater gastropod-faunas during the Neogene and Quaternary at species, genus and family levels, with emphasis on lakes. Currently, the database comprises over 8400 taxa, 5700 localities, 1490 lakes, 2000 references and 36,000 distribution records and can be accessed through http://www.marinespecies.org/freshgen/. The data are based on an in-depth literature review and the investigation of selected faunas. Aside from the analytical papers, 344 mollusc taxa have been treated in systematic and taxonomic papers. Of these 95 taxa were introduced as new species or as new names.Based on Miocene to Recent gastropod distributions, we show that the existence and evolution of biodiversity hotspots in inland-water systems are tightly linked to the geodynamic history of the European continent. Both past and present hotspots are related to the formation and persistence of long-lived lake systems in geological basins or to isolation of existing inland basins and embayments from the marine realm. The faunal evolution within hotspots highly depends on surface area and to a lesser degree on warm climate. During the Quaternary icehouse climate and extensive glaciations, limnic biodiversity sustained a severe decline across the continent and most former hotspots disappeared. Consequently, a major turnover event occurred at the Plio-Pleistocene boundary, related to the demise of long-lived lakes and of their rich, endemic faunas at the end of the Pliocene. In the subsequent intervals, little or no turnover was observed. We also observed a pattern of high segregation in Early Pleistocene communities, associated with the abundance of endemic species with small distribution ranges, and reflecting the provincial character of the aquatic freshwater systems at that time. This structured pattern disintegrated gradually towards the Middle Pleistocene and remained unstructured up to present. In particular, spatial patterns in the Last Interglacial and Holocene suggest a random recolonization of freshwater habitats mostly by generalist species following deglaciation. Thus, we find strong support that the distribution of European limnic gastropods, at least partially, carries the imprint of the last Ice Age. The differences in species richness and composition point towards a gradual, ongoing process of species recolonization after deglaciation. These data are a solid base to estimate the (future) anthropogenic impact on Holocene lake faunas.