A Glimpse in the Dark? A First Phylogenetic Approach in a Widespread Freshwater Snail from Tropical Asia and Northern Australia (cerithioidea, Thiaridae)

Thiaridae are a speciose group of freshwater snails in tropical areas including a high number of described nominal taxa for which modern revisions are mostly lacking. Using an integrative approach, the systematic status of a group of thiarids from the Oriental region, including the nominal species Melania aspera and M. rudis, is reassessed on the basis of shell morphology and biometry, radula dentition patterns, and reproductive biology along with molecular genetic methods. Our results suggest that populations from the Oriental region cannot be distinguished on the basis of shell morphology, radula characters and their reproductive mode and are monophyletic based on mitochondrial sequences. Hence, M. rudis with M. aspera are regarded as belonging to the same species along with several other nominal taxa that were previously included in M. rudis. Moreover, populations from Thailand and Australia, from where the species was not previously recorded, could be shown to form a monophyletic group together with samples from Indonesia. However, a generic affiliation with Thiara, in which the investigated taxa were often included in the past, was not supported in our phylogenetic analyses, highlighting the need for a comprehensive revision of the genus-group systematics of Thiaridae as a whole.