Molecular phylogeny of Chondrocyclus (Gastropoda: Cyclophoridae), a widespread genus of sedentary, restricted-range snails

Molecular phylogeny of the snorkel snail Rhiostoma housei, a species complex from Thailand with descriptions of three new species

Snorkel snails (genus Rhiostoma) are widely distributed in Indo-China and on the Malay Peninsula. The shell morphology is traditionally used for species identification yet in Thailand, the common snorkel snail, Rhiostoma housei, shows considerable variation in shell morphology within and between populations. Therefore species identifications and delimitations are difficult. We used two mitochondrial DNA fragments (COI and 16S rRNA) and morphological characters to delimit species and infer phylogenetic relationships of Rhiostoma housei s.l. from eight localities in Thailand, representing potential cryptic species suggested by earlier allozyme and karyological data. Results revealed four distinct clades from different geographic areas in Thailand. Species delimitation analyses confirmed the clades as four separate species and a geometric morphometric analysis demonstrated subtle but consistent conchological differences between the four clades. The high COI sequence divergences among the four clades (mean: 14.8%; range: 10.3–16.5%) further supported the species level recognition. As a consequence, three new species are described from Thailand: R. khoratense, sp. nov., R. nakwangense, sp. nov. and R. phunangense, sp. nov. ZooBank: urn:lsid:zoobank.org:pub:EE534749-9346-4972-BF2E-3B5D0EB8AED8

Systematic revision of the snorkel snail genus Rhiostoma Benson, 1860 (Gastropoda, Caenogastropoda, Cyclophoridae) with descriptions of new species

The snorkel snail genus Rhiostoma Benson, 1860 is comprised of terrestrial cyclophorid snails with wide-ranging species diversity and radiation in Southeast Asia. The typical characters of the genus are a depressed shell, a detached and descending portion of the last whorl with a distinctive peristomal breathing device attached, and a calcareous cup-shaped operculum. Herein, we have revised the systematics of extant species based on shell morphology combined with COI barcoding. From these thirty recognised species, twelve are described as new to science: R. ? amarapuraensesp. nov., R. anceyisp. nov., R. breviocollarsp. nov., R. ebenozosterasp. nov., R. cheliopegmasp. nov., R. furfurosumsp. nov., R. gnomus, sp. nov., R. lannaensesp. nov., R. laoensesp. nov., R. platymorphasp. nov., R. rhothonotaphrosasp. nov., and R. tigrinasp. nov. All conchological characters are provided via illustrations of type specimens and living snails, and descriptions of the shells and radulae. Phylogenetic analysis based on partial COI gene sequences strongly supports the designated morphospecies and a monophyletic Rhiostoma, confirming that all pterocyclinid snails with a calcareous, cup-shaped operculum belong to the same clade. A high intra-specific divergence was observed in R. jalorensis and R. housei populations from locations in close proximity, suggesting a lower dispersal and higher level of isolation. The low inter-specific divergence found in R. hainesi, R. samuiense, R. asiphon, and R. rhothonotaphrosasp. nov. supports their recent diversification and local adaptation, and is congruent with their marked morphological differences. Finally, nine formerly Rhiostoma-placed species were reclassified into either the genus Cyclotus or the genus Opisthoporus.

Climatic oscillations during the Mio/Pliocene epochs induced cladogenesis in the terrestrial snail genus Gittenedouardia (Mollusca: Gastropoda: Cerastidae) from South Africa

In South Africa, the terrestrial snail genus Gittenedouardia is the most species-rich member of the Cerastidae, where it is primarily distributed in the highly fragmented Afrotemperate and Indian Ocean coastal belt (IOCB) forest biomes. Phylogenetic relationships and cladogenetic events within the genus remain unstudied. In this respect, we reconstructed a dated phylogeny for eight Gittenedouardia species, and two populations identified to genus level using a combined mitochondrial (16S rRNA and COI) DNA sequencing dataset analysed using Bayesian inference and Maximum Likelihood framework. Furthermore, we investigated the population genetic substructure of the three widely distributed species (Gittenedouardia spadicea, G. natalensis and G. arenicola) for the COI locus, while also subsampling these species using the nuclear DNA ITS-2 locus. Phylogenetic results based on the combined mtDNA dataset supported the monophyly of Gittenedouardia and revealed three major clades and deep genetic structure among the three widely distributed species. Divergence-time estimates suggest that diversification within Gittenedouardia occurred during the middle Miocene/late Pliocene, a period characterised by a decrease in precipitation and the contraction of the Afrotemperate and IOCB forest biomes. We used two species delimitation methods, (PTP and STACEY) to infer putative species in G. spadicea, G. natalensis and G. arenicola. The two methods recovered a large number of evolutionary distinct units, with minimal consensus in the exact number of lineages. Our findings suggest the presence of undescribed diversity, necessitating the need for taxonomic revisionary work on Gittenedouardia. We discuss the climatic factors which may have contributed to the observed cladogenesis and compare our results with other studies of forest dwelling faunal taxa.