Insights into the Evolutionary History of an Extinct South American Freshwater Snail Based on Historical DNA

Abstract

Highly oxygenated freshwater habitats in the High Paraná River (Argentina–Paraguay) were home to highly endemic snails of the genus Aylacostoma, which face extinction owing to the impoundment of the Yacyretá Reservoir in the 1990s. Two species, A. chloroticum and A. brunneum, are currently included in an ongoing ex situ conservation programme, whereas A. guaraniticum and A. stigmaticum are presumed extinct. Consequently, the validity and affinities of the latter two have remained enigmatic. Here, we provide the first molecular data on the extinct A. stigmaticum by means of historical DNA analysis. We describe patterns of molecular evolution based on partial sequences of the mitochondrial 12S ribosomal RNA gene from the extinct species and from those being bred within the ex situ programme. We further use this gene to derive a secondary structure model, to examine the specific status of A. stigmaticum and to explore the evolutionary history of these snails. The secondary structure model based on A. stigmaticum revealed that most polymorphic sites are located in unpaired regions. Our results support the view that the mitochondrial 12S region is an efficient marker for the discrimination of species, and the extinct A. stigmaticum is recognized here as a distinct evolutionary genetic species. Molecular phylogenetic analyses revealed a sister group relationship between A. chloroticum and A. brunneum, and estimated divergence times suggest that diversification of Aylacostoma in the High Paraná River might have started in the late Miocene via intra-basin speciation due to a past marine transgression. Finally, our findings reveal that DNA may be obtained from dried specimens at least 80 years after their collection, and confirms the feasibility of extracting historical DNA from museum collections for elucidating evolutionary patterns and processes in gastropods.

Comparative Mitogenome Analysis of Two Native Apple Snail Species (Ampullariidae, Pomacea) from Peruvian Amazon

“…The secondary structure of the 12S rRNA of P. reevei ( Figure 6 ) and P. aulanieri ( Figure S3 ) had an identical organization of four structural domains, with Domain III as the most conserved region, allowing its successful PCR across a wide variety of taxa [ 48 ]. Here, we found that the structure of Domain III in P. reevei and P. aulanieri is similar to previous reports in other mollusks [ 27 , 49 , 50 , 51 ]. On the other hand, Domains I and II have been poorly studied and they were difficult to infer in both species.…”

Exploration of phylogeography of Monacha cantiana s.l. continues: the populations of the Apuan Alps (NW Tuscany, Italy) (Eupulmonata, Stylommatophora, Hygromiidae)

“…In some cases, the identity and relationships of extinct taxa have been addressed and clarified through study of ancient DNA from dried tissue (e.g. Villanea et al 2016; Vogler et al 2016). Unfortunately, this approach is not applicable for Mabille’s syntypes because they consist only of shells devoid of any dried tissue.…”

The South-American distribution and southernmost record ofBiomphalaria peregrina—a potential intermediate host of schistosomiasis

“…The radula and jaw were cleaned following a modification of the non-destructive method described by Holznagel (1998) and Vogler et al (2016) : the structures were separated from the mass of tissue and placed in 1.5-ml microtubes containing 500 µl NET buffer (1 ml 1M Tris pH 8.0, 2 ml 0.5 M ethylenediaminetetraacetic acid, 1 ml 5 M NaCl, 20 ml 10% (w/v) sodium dodecyl sulfate, 76 ml water) and 10 µl of Proteinase K (20 mg/ml) were added. The samples were then incubated at 37 °C with a subsequent renewal of the NET buffer and Proteinase K to verify the absence of tissue.…”