Aylacostoma guaraniticum

[Melanie]

Extinct in the Wild due to building of the Yacyretá Dam on the Paraná River.



www.macn.gov.ar/0b_publico/15notas/ayla/ayla.htm

[Melanie]

Only extant in captive holdings of Argentine Museum of Natural
Science. Increase in water depth changed the well-lit, clear bed with oxygenated water to dense growth of algae with muddy bottom.

[Peter]

From: oldwww.wii.gov.in/eianew/eia/dams%20and%20development/kbase/contrib/env242.pdf

Sedon, M. (2000). Molluscan Biodiversity and the impact of large dams. Prepared for Thematic Review II.1: Dams, ecosystem functions and environmental restoration. Report to IUCN Species Survival Commission. One of 126 contributing papers to the World Commission on Dams.

The surveys prior to the construction of the Parana Dam on the Parana river showed that there were endemic species present in the rapids. These species were threatened with extinction resulted from changes in the flow regime at Yacréta-Apipe rapids on the Parana River after the Parana Dam was constructed (Bertonatti, 1999). These species were taken into a captive breeding programme, and three taxa (Aylacostoma guaraniticum (Hylton-Scot, 1953) Aylacostoma chloroticum (Hylton-Scot, 1953) Aylacostoma stigmaticum (Hylton-Scot, 1953) are now extinct in the wild (Darrigan pers. comm; see Quintana, 1999; pers. Comm. For Action Plan).

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And from: intranet.iucn.org/webfiles/doc/archive/2001/IUCN850.pdf

Don E. McAllister, John F. Craig, Nick Davidson, Simon Delany and Mary Seddon. (2001). Biodiversity Impacts of Large Dams. Background Paper Nr. 1 Prepared for IUCN / UNEP / WCD). International Union for Conservation of Nature and Natural Resources and the United Nations Environmental Programme.

Table 3.4. Dam impacts on freshwater molluscs
Case studies: Yacyretá Reservoir (1600 km2. Parana River rapids, Argentina and Paraguay.
Biodiversity increases: None noted.
Biodiversity decreases: Species richness: 3 of 7 taxa from this group of prosobranchs in the river (genus Aylacostoma) are extinct in the Wild (EW). Only extant in captive holdings of Argentine Museum of Natural Science. Increase in water depth changed the well-lit, clear bed with oxygenated water to dense growth of algae with muddy bottom.
Source: Bertonatti (1999); Quintana (updates as pers. comm.).

[Sebbe]

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

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.

www.ncbi.nlm.nih.gov/pmc/articles/PMC5199097/

[koeiyabe]

www.iucnredlist.org/species/29611/9504659