Testing for non-adaptive radiations in European spring snails
In cooperation with Martin Brändle (Ecology, Marburg). Supported by DFG grants WI 1902/5-1 and BR 1967/6-1 within the SPP 1127 (Radiationen - Genese biologischer Diversität)
Recently, there has been an increased interest in the study of radiations. However, whereas one form of radiation - adaptive radiation - has been studied extensively, another form - non-adaptive radiation - is discussed controversially and poorly understood. In fact, the concept of non-adaptive radiation (i.e., diversification not accompanied by adaptation into various niches and resulting in a group of allopatric species) is rejected by some workers. Although specific and testable criteria have been proposed for this radiation, they have never been tested in a comprehensive and rigorous statistical fashion, partly because many radiations in continental animal groups (particularly in Europe) have been largely affected by human impact. A possible exception is the European spring snail genus Bythinella; a large monophyletic group with several proposed radiations that is distributed throughout the continent. Moreover, its presumed lack of morphological and niche differentiation makes it an ideal candidate for studying non-adaptive radiations. Based on extensive morphological, genetic, and ecological data, the goals of the current projects are to identify radiations, to test the previously proposed criteria for non-adaptive radiation and to test for potential gradual differences between adaptive and non-adaptive radiations.