Abstract
Walter Biese described Littoridina santiagensis Biese, 1944 (Cochliopidae) from Estero Dehesa in 1944 based exclusively on external shell features and a second allopatric population in Yeso Spring three years later. Since 2011 different samplings have been carried out at the type locality and have only provided specimens of the morphologically similar invasive mudsnail Potamopyrgus antipodarum Gray, 1843 (Tateidae), raising doubts about the identity of the species. The recent finding of two snail morphotypes in Yeso Spring, a thick shelled form congruent with type specimens of L. santiagensis and a slender one morphologically associable to P. antipodarum, allowed comparative studies, including the taxonomic analysis of additional populations with similar shell morphology occurring in central Chile. A DNA barcoding (COI) approach identified the slender form from Yeso Spring in Maipo Basin and a second population from the contiguous Rapel Basin indeed as the invasive P. antipodarum; however, L. santiagensis was recovered among species of Potamolithus Pilsbry, 1896 (Tateidae), justifying the Potamolithus santiagensis (Biese, 1944) comb. nov. Besides recognition of three other populations as belonging to Potamolithus, the molecular analysis also suggests trans-Andean dispersal of this group of snails in the Southern Cone of South America.
Highlights
The taxonomic placement of minute Chilean freshwater snails solely described based on morphological characters, such as Littoridina santiagensis Biese, 1944, is rather controversial
Two snail morphotypes could be recognized in Yeso Spring and Lo Carreño, a slender form morphologically associable to P. antipodarum and a thick-shelled one congruent with the type specimens of L. santiagensis, here transferred to Potamolithus based on anatomical characters and DNA barcode analysis
The minute native gilled freshwater snails in Chile, at present placed in the genera Littoridina, Heleobia or Potamolithus, have had a complicated taxonomic history, as they have been ascribed to the families Amnicolidae, Hydrobiidae, Littoridinidae and Cochliopidae (e.g., Pilsbry 1911; Biese 1944, 1947; Hershler & Thompson 1992; Valdovinos 1999, 2006; Figueroa et al 1999; Sielfeld 2001)
Summary
The taxonomic placement of minute Chilean freshwater snails solely described based on morphological characters, such as Littoridina santiagensis Biese, 1944, is rather controversial This species was described in the genus Littoridina Souleyet, 1852 by Walter Biese from Estero Dehesa, a small tributary of the Mapocho River located east of Santiago in the Maipo Basin, based on characteristics of the shell and for which only a single drawing is available from the original description (Biese 1944) (Fig. 1). Hershler & Thompson (1992), in their influential work on Cochliopinae, placed all the Chilean species of Littoridina, including L. santiagensis, in the genus Heleobia, but without providing arguments for this translocation. This was perhaps one of the reasons why several authors continued to consider these species as members of Littoridina (e.g., Sielfeld 2001; Valdovinos 1999, 2006, 2008)
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