Unravelling the tangle of the azecid land snails: a survey on the supraspecific systematics based on comparative morphology and molecular phylogeny (Gastropoda: Eupulmonata: Orthurethra)

A selection of 17 azecid species, including Azeca goodalli, Gomeziella girottii, Hypnocarnica micaelae, four species of Cryptazeca and ten species currently assigned to Hypnophila, chosen among those best known, were investigated to elucidate their relationships based on morphological and molecular evidence. Thirty one characters, only 15 of which were parsimony informative, were scored from morphology. Parsimony analysis was performed with PAUP* 4.0 using Cochlicopa lubrica as outgroup. Sequences of COI and ITS2 deposited in GenBank were re-examined using Cochlicopa lubrica as outgroup. Phylogeny based on the morphological characters suggested that Hypnophila as formerly conceived was a polyphyletic taxon with four different lineages: Gomeziella girottii (1); Hypnophila boissii (2); the Dalmatian Hypnophila species except H. zirjensis (3); the western Mediterranean species plus H. zirjensis (4). Unfortunately molecular studies did not include Gomeziella girottii and species of Dalmatian Hypnophila and this biases full comparison between the two data sets. Moreover our re-analysis of the previous molecular data produced a slightly different phylogenetic hypothesis compared to the original one. Indeed, the only ML tree of COI sequences confirmed with weak bootstrap supported the phylogenetic hypothesis that Hypnocarnica micaelae was the sister group to all the other azecids. On the contrary, the ML trees of ITS2 and of concatenated COI+ITS2 sequences found that Azeca goodalli was the sister group to all the other azecids, Cryptazeca was paraphyletic and Hypnocarnica micaelae was the sister group of Cryptazeca monodonta. Comparing the results of the two data sets, it emerged that phylogenetic analysis based on morphological characters had good resolution but very low statistical support and that the position of Hypnophila boissii was the most variable. In morphological phylogeny this species had unresolved relationships with Gomeziella girottii and a clade including Azeca goodalli and all other species currently assigned to Hypnophila, whereas in the molecular phylogeny it was nested in the western Hypnophila. The latter result is followed here assigning the species now included in Hypnophila to two distinct genera: Gomphroa comprising the western species plus Hypnophila zirjensis; Hypnophila including the Dalmatian species except Hypnophila zirjensis.