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Sarika costabilis und Sarika costata, PHOLYOTHA et al 2022

BeitragVerfasst: 21.04.2022 pm 15:07
von notho2
in Contributions to Zoology
Online-Publikationsdatum: 21 Mar 2022

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


Arthit Pholyotha1, Chirasak Sutcharit2, Aung Lin3, und Somsak Panha4,5


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.

Figure 3
Shells of Sarika spp. A, B) S. theodori. A) Specimen nhmuk 1988.12.4.1514. B) Specimen cumz 7941. C, D) S. siamensis. C) Specimen cumz 7949. D) Specimen cumz 7950.

Citation: Contributions to Zoology 91, 2 (2022) ; 10.1163/18759866-bja10027


Mainland Southeast Asia is recognized as an important biodiversity hotspot (Myers et al., 2000), and the limacoid land snail genus Sarika Godwin-Austen, 1907, a taxonomically diverse group, is well represented in this region (Blanford & Godwin-Austen, 1908; Schileyko, 2002; Pholyotha et al., 2020a, b, c). Recently, modern systematic revision of the genus Sarika has been carefully studied (Pholyotha et al., 2020a, b, c). The genus is monophyletic and all members have a smooth and polished shell and general soft anatomy with a straight epiphallic caecum, short to long flagellum, long spermatheca and a large dart apparatus (Pholyotha et al., 2020a, b, c).

Surprisingly, during an examination of land snails with a ribbed shell surface, Hemiplecta theodori (Philippi, 1846) from Myanmar (Blanford & Godwin-Austen, 1908; Sutcharit & Panha, 2021) and Cryptozona siamensis (Pfeiffer, 1856a) from Thailand (Panha, 1996; Boonmachai & Nantarat, 2020) were found to exhibit distinct genital characters from their current accepted generic assignment. Rather, their genitalia were similar to those of Sarika s.s. Therefore, these two nominal species seemed to have a systematic ambiguity between the shell- and genitalia-based taxon descriptions. In general, the use of only shell traits may cause confusion or misidentification, as reported previously in several terrestrial snails (i.e., Köhler et al., 2020a, b; Jirapatrasilp et al., 2021; Pholyotha et al., 2021; Sutcharit et al., 2021).

Traditional shell-based taxonomic placement has largely remained hypothetical awaiting confirmation from additional sources of evidence. In particular, the genital characters can distinguish taxa at both the generic and specific levels and are known to reflect their evolutionary positions more accurately than shell traits do (Hirano et al., 2014; Hyman et al., 2017; Köhler & Criscione, 2015; Pholyotha et al., 2020c, 2021; Jirapatrasilp et al., 2021; Sutcharit et al., 2021). In addition, molecular methods of species delineation have been widely and successfully used to clarify the evolution of land snails (Hyman et al., 2017; Liew et al., 2009; Köhler & Criscione, 2015; Hyman & Köhler, 2018), including otherwise ambiguous species.

At present, the genus Sarika might contain members that have a smooth shell surface and those have a ribbed shell surface. The implications of these two morphotypes (smooth and ribbed shell surfaces) have not been studied systematically and comprehensively in the context of the taxonomy of this genus. As a next step towards enhancing our understanding of the systematic relationships of this genus, therefore, we consider it important to clarify the current shell-based taxonomy of the genus Sarika using both morpho-anatomical characters and dna sequence information, the latter based on the mitochondrial cytochrome c oxidase subunit I (coi) gene, the large subunit ribosomal rna (16S) gene, and the partial 28S nuclear rDNA (28S) gene. In addition, this work includes taxonomic updates, illustrations of type specimens (when possible), the distribution ranges, and descriptions of the living snails, shells, genitalia, and radula. Moreover, two species of Sarika with a ribbed shell surface are herein described as new to science.

Figure 8
Shells of Sarika spp. A, B) S. costabilis sp. nov. A) Holotype cumz 7943. B) Paratype cumz 7944. C, D) S. costata sp. nov. C) Holotype cumz 7946. D) Paratype cumz 7947.

Citation: Contributions to Zoology 91, 2 (2022) ; 10.1163/18759866-bja10027

Materials and methods

Sampling, material preservation, identification, and morphological examination
All the Sarika specimens included in this study were obtained from the Chulalongkorn University Museum of Zoology (cumz), Bangkok, Thailand. Sarika siamensis had been collected since 1994 from various locations in mainland Southeast Asia, while S. costabilis sp. nov. was collected during field surveys in 2016 from western Thailand (fig. 1). Sarika theodori and S. costata sp. nov. were each collected from southern Myanmar (fig. 1) during 2016 and 2017 under an mou (Letter No. 0092) between the Forest Department, Ministry of Natural Resources and Environmental Conservation and Forestry, Myanmar, and the Fauna & Flora International.