The Caucasus is neither a cradle nor a museum of diversity of the land snail genus Helix (Gastropoda, Stylommatophora, Helicidae), while Crimea is home to an ancient lineage

Abstract

The Caucasus and the adjacent Pontic Mountains in north-eastern Anatolia are home to numerous endemic land snail genera and species. The diversity of the region is the result of both intra-regional speciation and the persistence of relict lineages. The same seemed to be true for the genus Helix, which has been present in the Greater Caucasus since the Miocene. In the Caucasus region, there are three Helix species. Helix buchii (Pontic Mountains and Georgia) and Helix albescens (southern Ukraine to northern Lesser Caucasus) are both separated by deep splits from the major Helix clades in the mitochondrial phylogeny. In contrast, Helix lucorum belongs to the Anatolian radiation of Helix. At least part of its intraspecific diversification may have occurred in north-eastern Anatolia and the adjacent parts of the Caucasus. Here, we report new evidence suggesting that the Caucasus and the Pontus regions were less important as a refugium of ancient Helix lineages or as a diversification centre than previously hypothesised. Helix lucorum probably diversified more westwards, while H. buchii is a less ancient lineage than previously thought. Helix albescens had its long-term refugium on the Crimean Peninsula in southern Ukraine, not in the Caucasus. The Caucasus is close to the eastern limit of the distribution range of the genus and, although the fossil record shows that Helix was present there as early as the Miocene, the current diversity of the genus there is the result of much later colonisation.