Phylogenetic position of the relict South American genus Idiopyrgus Pilsbry, 1911 (Gastropoda, Truncatelloidea), with the description of two new cave species

Abstract

Idiopyrgus is a relict genus of freshwater snails from Brazil traditionally classified in the family Pomatiopsidae. Herein, we use molecular data from newly acquired specimens to test that classification through Bayesian inference phylogenetic analysis. We conclude that Idiopyrgus belongs in the Gondwanan family Tomichiidae, together with the African genus Tomichia and the Australian genus Coxiella. Furthermore, we reassess currently synonymized genus- and species-level names in Idiopyrgus. The genera Hydracme and Aquidauania are considered synonymous with Idiopyrgus. The species I. brasiliensis and I. pilsbryi are restored as accepted species; I. walkeri is considered a taxon inquirendum. Two new species from caves in Bahia state are described herein: Idiopyrgus adamanteussp. nov. and Idiopyrgus minorsp. nov.

Taxonomic study on a collection of terrestrial and freshwater gastropods from caves in Bahia state, Brazil, with the description of a new species

“…As recently suggested in the study of SalvadoR et al (2022a), it is also notable that the caves in Bahia state could be a hotbed of speciation of Idiopyrgus, an otherwise low-diversity relict genus. Besides the three species reported herein (Table 1), I. souleyetanus Pilsbry, 1911 also occurs in Bahia, totaling four out of the seven currently-recognized species in the genus (SalvadoR et al 2022a).…”

“…The previously reported trend of Achatinidae (Subulininae) and Scolodontidae being the most diverse terrestrial families in caves (e.g., SalvadoR et al , 2017SalvadoR et al , 2021 is further supported by our data (Table 1). Nevertheless, it is worth noting that most representatives of those families in caves belong to widespread species in the country (SalvadoR et al 2022a).…”

“…Among the freshwater snails, there are more cave endemics and potentially troglobiotic species (e.g., Idiopyrgus minor), likely due to the populations becoming isolated. In those cases, it is also common to find morphoanatomical features that are probably troglomorphisms, such as translucent shells and lack of body pigmentation (Figs 10-13;SalvadoR et al 2022a, b). Even though Plesiophysa sp.…”

“…Given that the region might be a hotspot for snails and other invertebrates (tRajano & Bichuette 2009, the current lack of protection of the caves studied herein is worrying. The caves in the regions of Central municipality and Serra do Ramalho, for instance, are impacted by deforestation, agriculture, and mining, which increasingly shows the need for fauna studies in these places (gallão & Bichuette 2018, 2022a.…”