Diversity and structure of fish communities in the large lakes of the Alps
Fish communities in large deep lakes are of major ecological, evolutionary, commercial, conservation and recreational value. They are exposed to many anthropogenic stressors and change rapidly. We are studying environmental predictors of species richness and endemism using large data sets that we have compiled over many years. We work with a large data set for cichlid fish diversity of all major and many small lakes of Africa and with a large data set for all fish of most of the larger lakes north and south of the Alps. We are also working on fish in lakes of Greenland. In all these systems we wish to understand causes of variation in species diversity and functional ecological diversity. Eventually we wish to understand how variation in diversity affects the lacustrine ecosystems.
To identify the forces behind variation and change, quantitative fish community data is crucially needed. Surprisingly, such baseline data needed for studying lake fish community changes was lacking for most lakes in Switzerland. In 2010 we launched Projet Lac to collect and compile quantitative baseline data for most large lakes of Switzerland and neighboring countries. We designed methods for a full quantitative sampling design and applied them to twenty six medium to large and very deep lakes. We apply a fully nested biodiversity sampling and assessment, whereby the aim is to document and assess diversity at all its fundamental levels. These include individual genetic and phenotypic diversity within populations for several key taxa, species diversity and abundance, community diversity by habitats and whole lake diversity. A large state-of-the-art collection of pre-alpine fish is being established at the Natural History Museum in Bern. We are now analyzing the species distribution and abundance data and are beginning to collect phenotypic and genetic data. Eventually we want to explain the massive changes in species diversity and distribution observed over the last years, and we want to understand if these changes affect ecosystem functions.
Fish communities in most larger lakes, both in the tropics and the Alps and polar regions are a mixture of species that arrived by immigration and others that evolved locally through radiation of one colonizing species into several species. We would like to understand whether both processes are distinct in their effects on patterns in resource utilization and ecosystem function.
AquaDiverse was funded by Eawag over several years and contributed importantly to our early work on the whitefish in the deep lakes of the Alps. This work led to the discovery of the mechanisms behind rapid collapse of whitefish species diversity in many lakes. It also started a series of ecosystem experiments in outdoor mesocosm tanks where we investigated effects on lower tropic levels and on the ecosystem of phenotypic and genetic differentiation among sympatric whitefish species. This work is in collaboration with Dr Blake Matthews. These experiments are since being continued with stickleback.