Aylacostoma, SNAILS

Vogler, Roberto E., Beltramino, Ariel A., Strong, Ellen E., Peso, Juana G. & Rumi, Alejandra, 2015, A phylogeographical perspective on the ex situ conservation of Aylacostoma (Thiaridae, Gastropoda) from the High Paraná River (Argentina-Paraguay), Zoological Journal of the Linnean Society 174 (3), pp. 487-499 : 494-495

AYLACOSTOMA SNAILS

One of the primary goals of conservation biology is to ensure the maintenance of biodiversity, of which genetic diversity is a fundamental component ( DeSalle & Amato, 2004). An efficient conservation programme should include unequivocal identification of management units representing different evolutionary lineages, for which genetic information provides an objective means to determine conservation priorities ( King & Burke, 1999; DeSalle & Amato, 2004). In the present study we have identified three evolutionary lineages among Aylacostoma representatives from the High Paraná River. While A. brunneum was only recently described ( Vogler et al., 2014), we suggest the two haplotypes found in A. chloroticum deserve special attention as independent lineages. Although the geographical populations where these haplotypes occur do not qualify under the strictest definition of evolutionarily significant units (ESUs; Ryder, 1986; Moritz, 1994; Ladle & Whittaker, 2011), we suggest that the two haplotypes of A. chloroticum (H 1 and H 2) should be recognized as ESUs in a broad sense. This proposition is based on the fact that captive populations derived from single individuals containing these haplotypes represent independent evolutionary histories reflecting the apomictic parthenogenetic reproductive mode of the species. Al- though no morphological differentiation among the haplotype lineages has been observed ( Vogler et al., 2014), the apparent persistence of these lineages since the Pleistocene may be indicative of an incipient speciation event.

In this context, understanding the geographical distribution of genetic diversity in the High Paraná River is vital for identifying and prioritizing areas for protection, so that the genetic representation of Aylacostoma in nature can be maximized. Our analysis clearly shows that the entry zone of the Yacyretá Reservoir, and particularly Río Beach, is an area of great interest in terms of conservation. This is where A. brunneum was found, and is where the two haplotypes of A. chloroticum converge. Thus, this area deserves to be highlighted as a key genetic resource for the ex situ conservation of the group. It is important to emphasize that the filling of the Yacyretá Reservoir was completed in 2011. Although the entry zone was less impacted by the new water levels, what little genetic variation has been de- termined here for this area may have already been lost. This highlights the urgent need to survey the area and fully justifies the ex situ efforts to preserve the available diversity of A. chloroticum and A. brunneum , both of which deserve the highest priorities for conservation.

Finally, by considering our results and taking into account the ongoing efforts of the ‘ Aylacostoma Project’ in which re-introduction of captive-bred individuals and field translocations are being attempted, we suggest that such actions should be made, whenever possible, in available areas of the entry zone, to preserve as much as possible the future evolutionary potential of the extant diversity.