Lakes and Quaternary lake deposits in Anatolia and the Balkans contain various groups of Pontocaspian taxa. However, it remains largely unknown whether these satellite areas served as sink or source (cf. refuges) for Pontocaspian biota. Combined molecular phylogenetic analyses of extant Pontocaspian species from Anatolian and Balkan lakes with a rigorous updated study of fossil successions and their depositional/geochemical context in these lake basins will allow testing their role as sinks and/or sources. The environmental context of biotic change in selected lake successions will be determined through sedimentological and geochemical analyses (through projects A4, B5) and supplemented by ostracod data from project B2.