Phylogenetic relationships and description of a new stygobite species of Bythinella (Mollusca, Gastropoda, Caenogastropoda, Amnicolidae) from southern France Vincent PRIÉ Université Pierre & Marie Curie, « Systématique, Adaptation, Évolution », UMR 7138 – CNRS – Paris VI – MNHN – IRD, Équipe « Génétique et Évolution », bât. A, porte 427 – case 5, 7 quai Saint-Bernard, F-75252 Paris cedex 05 (France)
[email protected] Jean-Michel BICHAIN Muséum national d’Histoire naturelle, Département Systématique et Évolution, USM 603/UMR 7138 « Systématique, Adaptation, Évolution », Équipe « Exploration de la Biodiversité », case postale 51, 57 rue Cuvier, F-75231 Paris cedex 05 (France)
[email protected] Prié V. & Bichain J.-M. 2009. — Phylogenetic relationships and description of a new stygobite species of Bythinella (Mollusca, Gastropoda, Caenogastropoda, Amnicolidae) from southern France. Zoosystema 31 (4) : 987-1000. ABSTRACT A population of the aquatic gastropod Bythinella that does not conform to any described hypogean or epigean species of this genus was discovered in a cave stream in southern France (Folatière cave). Members of this population lacked body pigments and eyespots, which suggests adaptation to a subterranean environment. Mitochondrial COI sequences revealed two lineages within this population, separated by a genetic divergence higher than the inter-specifi c threshold commonly admitted for hydrobioid species. In contrast, a phylogeny based on the nuclear ITS1 gene clustered the sequenced hypogean specimens in a single clade. Moreover multivariate analyses performed on shell parameters did not enable discrimination between hypogean specimens attributed to each of these two mitochondrial lineages. Th e high COI variability within the same population and confl ict between mtDNA and nDNA trees could be explained by a scenario of introgression by hybridization.