Lessons from Timor: Shells are poor taxonomic indicators in Asperitas land snails (Stylommatophora, Dyakiidae)

Deciphering “cryptic” nature of European rock-dwelling Pyramidula snails (Gastropoda: Stylommatophora)

Many molecular phylogenetic studies conclude by reporting discoveries of new “cryptic” species. However, these putative biological entities are typically left unverified outside of the dna evidence or subjected to only superficial post-hoc analyses. Minute land snails of the Western Palearctic Pyramidula represent one of such examples being considered a cryptic species complex based on previously conducted molecular phylogeny. Several species appear indistinguishable due to noticeable shell tendency towards either high-spired (Pyramidula rupestris and P. jaenensis) or low-spired (P. saxatilis and P. pusilla) morphotype. Here, we challenge this conclusion by using mt DNA, n DNA, morphometric analyses and qualitative shell features, and seek for a potential evolutionary mechanism behind the conchological similarities. Through an empirical integration of multiple data types we document that the studied taxa can be visually distinguished. Unlike isolated shell measurements, cva s based on traditional morphometrics and geometric morphometrics have power to separate all species from each other, except for P. saxatilis and P. pusilla. However, only a use of previously overlooked shell surface microsculpture makes it possible to identify individuals of all species. Considering tight associations between shell measurements and climate, we propose an evolutionary explanation based on optimization of thermal flux under different climatic selection pressures. Our study brings the awareness towards microscopic shell features, and outlines a general protocol to identify robust visual identification criteria in taxonomic groups containing cryptic (and non-cryptic) members. It also exemplifies an integration of various data types for macroscale species identification, which we believe should follow any discovery of putatively cryptic species.

Multigene phylogeny reveals the ribbed shell morphotypes in the land snail genus Sarika (Eupulmonata: Ariophantidae), with description of two new species from Thailand and Myanmar

The speciose land snail genus Sarika is widely distributed throughout mainland Southeast Asia. This genus is generally recognized by a smooth and polished shell. However, we recognize four species with a ribbed shell surface (S. siamensis, S. theodori, S. costabilis sp. nov., and S. costata sp. nov.) exhibiting genital characters similar to those of Sarika s.s. and so a rearrangement in the systematics of the genus is suggested. Here, we analysed these four ribbed shell species together with Sarika s.s. by a combined morphological and molecular approach to species delineation, the latter based on both mitochondrial (coi and 16S) and nuclear (28S) markers. Our molecular phylogeny affirms the monophyly of the genus Sarika including both smooth and ribbed shell morphotypes that is statistically well supported. The ribbed shell morphotype in the land snail genus Sarika is also well defined in terms of diagnostic morpho-anatomical characters that can be divided into two species groups. The S. costata species group consists of only one species, S. costata sp. nov., while the S. siamensis species group comprises S. siamensis, S. theodori and S. costabilis sp. nov. These findings provide a solid basis for the systematics of family Ariophantidae.

Molecular phylogeny of the limacoid snail family Dyakiidae in Southeast Asia, with the description of a new genus and species

Members of the terrestrial snail family Dyakiidae from Southeast Asia show a distinct geographical distribution pattern and possess different degrees of complexity in their amatorial organ gland. This study is the first molecular phylogeny of ten of the 12 genera in this family, performed to provide insights into the origin of Dyakiidae and the evolution of their shells and amatorial organ gland structure. A new genus and new species, Pseudoquantula lenticularis Jirapatrasilp & Panha gen. & sp. nov., was uncovered based on its distinct morphological characters and molecular divergence. All other genera were retrieved as monophyletic except for Dyakia. Mainland Southeast Asia was inferred to be the ancestral range of the Dyakiidae, and the lineages then dispersed to and diversified in Borneo. Cladistic analysis showed that all 14 morphological characters used in this study were homoplastic. These results disagree with the previous amatorial organ transformation series, in which neither Pseudoplecta nor Quantula was ancestral to the other genera. The enigmatic genus Pseudoplecta, which lacks an amatorial organ gland, exhibited secondary loss.