Star-like radiation of Leucostigma candidescens populations (Gastropoda: Clausiliidae) and repeated changes in chirality

Leucostigma candidescens is a rock-dwelling door snail species, which is widespread in the central and southern Apennines of Italy. The species has been divided into nine subspecies. Three of them are characterized by a change in the coiling direction, which is usually a rare evolutionary event. We generated restriction site-associated DNA markers from 27 populations of L. candidescens to investigate its population structure, the fit of subspecies classification to population structure, and the origin and frequency of changes in coiling direction. The populations of L. candidescens diverged in a star-like radiation, partly associated with long-distance events. The subspecies do not correspond to deep phylogeographic subdivisions, but are artificial combinations of populations characterized by similar combinations of morphological characters. The coiling direction changed in parallel in three populations of L. candidescens. The population structure of rock-dwelling land snails, with small populations and little gene flow, is conducive to establishing populations with a mutant coiling direction.