Phylogenetic relationships of Iberus gualtieranus and I-Alonensis (Gastropoda: Helicidae) based on partial mitochondrial 16S rRNA and COI gene sequences

There is controversy about the phylogenetic relationships between Iberus gualtieranus and I. alonensis. Some authors consider them as valid species or subspecies while others believe that the flattened shell of I. gualtieranus is an ecotypic adaptation to dry karstic environments. Two fragments of the mitochondrial DNA (partial COI and 16S rRNA) were sequenced and used in maximum parsimony, maximum likelihood and neighbour-joining analyses. Iberus alonensis show two distinct lineages, one from Almeria and the other one from Granada and Jaen-Cordoba regions. Iberus gualtieranus populations are recovered as a terminal node within the I. alonensis group from Almeria. The I. gualtieranus clade shows a polytomy and there are no differences between the populations of the three isolated localities where I. gualtieranus is currently distributed. This indicates that the geographical isolation of these populations has not resulted in genetic diversification. The results indicate that the population of I. gualtieranus from Sierra de Gador in Almeria is the only autochthonous one, while the other two populations originated by historical introductions. On the basis of the differences in shell morphology, together with the presence of a hybrid zone connecting both taxa in nature, and the possibility of obtaining fertile hybrids under laboratory conditions, we conclude that these two taxa represent two subspecies: Iberus gualtieranus gualtieranus and I. gualtieranus alonensis.