Molecular phylogeny of the panpulmonate groups Stylommatophora and Hygrophila.


Ahmed J. Saadi

Postdoc: Phylactolaemate phylogenomics (PD Dr. Thomas Schwaha)

Unit for Integrative Zoology, Department of Evolutionary Biology
University of Vienna

The phylogenetic relationships at the base of the stylommatophoran land snails and slugs have proven to be controversial, particularly the position of the Scolodontidae. Likewise, the phylogenetic relationships within the hygrophilan freshwater snails and limpets are uncertain. This study provides molecular phylogenies for the Stylommatophora and Hygrophila at multiple scales including deep phylogenetic relationships of the major stylommatophoran and hygrophilan clades and family level relationships within the Orthurethra and Lymnaeoidea.

We have investigated the phylogenetic relationships of the basal divisions within the Stylommatophora using five standard markers: the 18S, 5.8S, 28S rRNA, H3 and CO1 genes. The deep phylogenetic relationships at the base of the Stylommatophora are now clearly resolved. The Scolodontidae are shown categorically to be the sister group to all other stylommatophoran taxa with robust support and with all phylogeny reconstruction methods. Based on this result, a taxonomic revision for the basal groups within the Stylommatophora is proposed.

We have also undertaken a comprehensive molecular phylogenetic analysis of the Hygrophila based on the 5.8S and 28S rRNA genes. A clear basal division between Chilinoidea and Lymnaeoidea is observed. The monophyly of Acroloxidae, Lymnaeidae and Physidae is also well established. However, the Planorbidae are not supported as a monophyletic group, because the Bulinidae cluster within Planorbidae. A new taxonomic revision of the Hygrophila is proposed based on the findings of this molecular phylogeny.

The interrelationships among the lymnaeoidean families are reasonably well resolved using rRNA genes, though they are not fully supported. Therefore, to better resolve these relationships we have undertaken a more detailed phylogenomic analysis based on transcriptome sequences data for a representative from each of the main lymnaeoidean families. The observed interrelationships among the lymnaeoidean families based on the phylogenomic analysis are well resolved and consistent with those obtained based on the standard markers.