Isolation and endemism in the subterranean aquatic snails of the genus Belgrandiella A. J. Wagner, 1928 (Caenogastropoda: Truncatelloidea: Hydrobiidae).

The Western Balkans hosts the richest subterranean aquatic gastropod fauna in the world. The main factors shaping intraspecies diversity are thought to be isolation and endemism. In the genus Belgrandiella, minute snails inhabiting subterranean waters and springs in Central Europe and Balkans, molecular studies have shown much fewer valid species than previously anticipated. The present study applies mitochondrial cytochrome c oxidase subunit I, histone 3, and RAPD analysis, to check the inter- and intraspecies genetic diversity in 36 Belgrandiella populations from caves, springs and interstitial aquifers. The level of gene flow is assessed to check if these snails form a widespread genetically uniform metapopulation or rather follow the highly endemic pattern. The studied populations have been assigned to six species. In the most widely distributed B. kusceri from 21 populations, 60 sequenced specimens represent 16 haplotypes. While the same haplotypes are present in distant populations, gene flow between the other populations is low. Nei distances for RAPD show no geographic pattern. The interspecies differences in COI evidently confirm the time of speciation in Pleistocene, before karstification, which rejects speciation within isolated caves. The pattern observed in Belgrandiella seems more similar to the one described in Montenegrospeum than in Kerkia. [ABSTRACT FROM AUTHOR]