ИСТИНА

The Pontocaspian fauna is an anomalohaline fauna dominated by endemic neritiid and hydrobiid gastropod species and lymnocardiine and dreissenid bivalve species living in the Black Sea, Caspian Sea and formerly Aral Sea Basin. Some Anatolian lakes also include Pontocaspian species1. The fauna is experiencing severe decline, hi the Black Sea basin the development of coastal wetlands and pollution diminish suitable habitat2, possibly aggravated by introduced species. The intended as well as unintentional introduction of Mediterranean species in the Caspian Sea since the 1930ties has dramatically changed the formerly endemic communities3'4. Possibly a major extinction has occurred in the past century especially in poorly understood endemic groups such as hydrobiid snails. The desiccation of most of Lake Aral too has resulted in the decline of the Pontocaspian fauna there. The Pontocaspian fauna has experienced severe turnover events in its geological past. The modern fauna assembled in the middle Quaternary in the Black Sea and Caspian Sea basins. Several of the taxa (mostly genera) that now typify the Pontocaspian fauna derived from paratethyan lake systems such as the Pontian-Dacian system (several of the hydrobiid and dreissenid lineages1'5, from rivers in the Pontocaspian drainage basin (possibly neritine and dreissenid lineages), but several derived from Neogene Anatolian lake systems (some hydrobiid and two lymnocardiine lineages6'7). We present new data that indicate faunal exchange between the Pontocaspian domain and the Anatolian lake systems during the Quaternary. By documenting successive Pontocaspian faunas in the different basins, the documentation of turnover events and studying their paleogeographic, environmental and climatic context we aim to elucidate the resilience of the fauna in past adverse conditions. A comparison with the modern, human-mediated Pontocaspian biodiversity crisis is made.