Abstract
In the present study, we focus on the phylogeographic pattern, demographic history and morphological differentiation of Heleobia ascotanensis, a freshwater gastropod restricted to the Ascotán saltpan in the Chilean Altiplano. The current distribution of the species is limited to twelve isolated or partially isolated springs that were affected by transitions between humid and arid periods during last glaciations. The genetic analysis of 322 specimens showed that H. ascotanensis is subdivided into three genetically divergent populations, with low and moderate degrees of historical gene flow among them and incipient morphological differentiation as a consequence of genetic and geographical isolation. Molecular analyses revealed different demographic histories among populations which seem to respond independently to climatic events, probably due to an environmental imposition and idiosyncratic strategies developed to cope with water availability. The results of this study and co-distributed taxa support the hypothesis that contemporary and historical events have influenced microevolutionary differentiation of these snails, although there is a need to complement further information to predict genetic or morphological divergence at microgeographic scale.
Highlights
The physiography of the South American Altiplano landscape is characterized by several closed basins mainly originated by a high volcanic activity that took place since the Miocene, accompanied by complex climatic events (Fornari, Risacher & Féraud, 2001; Risacher, Alonso & Salazar, 2003; Strecker et al, 2007; Placzek, Quade & Patchett, 2011; Placzek, Quade & Patchett, 2013)
We examined the phylogeographic and demographic history of H. ascotanensis from the Ascotán saltpan to test whether this species shows population structure and whether this structure is associated with the physiography of the saltpan or it responds to past climatic events
The analysis of molecular variance (AMOVA) identified significant values for the genetic variance at the two levels tested
Summary
The physiography of the South American Altiplano landscape is characterized by several closed basins mainly originated by a high volcanic activity that took place since the Miocene, accompanied by complex climatic events (Fornari, Risacher & Féraud, 2001; Risacher, Alonso & Salazar, 2003; Strecker et al, 2007; Placzek, Quade & Patchett, 2011; Placzek, Quade & Patchett, 2013). Contrasting the actual hydrographic conditions on the Altiplano mainly modulated by the SASM, during the Pleistocene most of the region was covered by great paleolakes over 3.650 m altitude (influenced by global glaciations), which connected numerous hydrographic basins currently disconnected (Lavenu, Fornari & Sebrier, 1984; Fornari, Risacher & Féraud, 2001; Blard et al, 2011; Placzek, Quade & Patchett, 2013). With the transition of humid periods that characterized the Plio-Pleistocene to dry seasons prevailing during the Holocene, the aquatic environments were fragmented causing the isolation of populations confined to these systems (e.g., Keller & Soto, 1998)
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