Systematics and biogeography of land snails, genus Sarika godwin-austen, 1907 (pulmonata: ariophantidae: macrochlamydinae) in Thailand

An in-depth study of the taxonomy, systematics, and biogeography of the land snail genus Sarika Godwin-Austen, 1907 was conducted based on snail samples collected from karstic and non-karstic habitats throughout Thailand and from several areas of neighboring countries in mainland Southeast Asia. The taxonomic revision, based on the comparative analyses of traditional morphological and anatomical characters combined with the molecular phylogenetic analyses of three partial gene datasets (COI, 16S rRNA, and 28S rRNA), was used to verify the validity of this land snail group. A total of 23 species of Sarika were recognized in Thailand, of which 17 species are now updated for their essential taxonomic information. The molecular analyses showed a high degree of node support for the monophyly of all species. Almost all of the species were restricted to limestone karsts and outcrops, but some species can also be found in other habitats (e.g. sandstone, granitic, or forested mountainous areas). Most of the species are regarded as locally endemic from their narrow distribution range (except the region cosmopolitan species S. resplendens). Additionally, the multi-locus phylogeny reconstructions revealed that the genus Sarika sensu lato is polyphyletic, since it is composed of at least two divergent lineages. From the species previously classified as belonging to Sarika, known as the Crown Snails, genus Taphrenalla is now described herein as a distinct genus from Sarika on the basis of their distinctive morphological characteristics and high genetic divergences. The total number of Crown Snails is currently bought up to 11 species. Interestingly, all Taphrenalla species are endemic to limestone karsts and outcrops scattered along the two main mountain ranges of Southern Thailand. Based on the biogeographic analysis, the spread of ariophantid lineages into Southeast Asia may happen after the collision of the Indian sub-continent with Eurasia in the Oligocene. The results suggested that the geographic origin of the Sarika lineages may be in the Indo-Burma regions during the Miocene and Pliocene, and then underwent speciation and radiation of these lineages with likely migration southeastwards and southwards to Thailand during the Pliocene and Pleistocene.