Exploring a largely unknown fauna: On the diversity of pachychilid freshwater
A revision of Vietnamese freshwater gastropods of the family Pachychilidae is presented based on the analysis of morphological characteristics and partial sequences of the mitochondrial genes of 16S rRNA (16S) and cytochrome c oxidase subunit I (COI). We found that in Vietnam two pachychilid genera occur, Brotia and Sulcospira. Of the eight to fifteen species reported by earlier authors, we can only confirm the presence of two species, Sulcospira tonkiniana and S. tourannensis. All further taxonomic names that were previously applied for Vietnamese pachychilids are considered as junior synonyms of these two species or erroneous references to species from other regions of Southeast and South Asia. Additionally, we describe two new species of Brotia, four new species of Sulcospira, and report another undescribed species with uncertain affinities. Patterns of morphological and genetic differentiation of the Vietnamese species and their affinities within the context of pachychilid phylogeny are briefly discussed.