Molecular evidence of ice-age refugia in the Patagonia steppe and post-glacial colonization of the Andes slopes: insights from the endemic species Calceolaria polyrhiza (Calceolariaceae).

COSACOV A.; SÉRSIC A. N.; COCUCCI A. A.; SOSA V.; JOHNSON L.A

Bariloche

Simposio; Southern Connection Congress; 2010

Southern Connection

Species widespread throughout historically glaciated and non-glaciated areas provide excellent systems to investigate the role of past climatic changes on the distribution of contemporary biodiversity. However, such studies are scarce for plants of the Southern Hemisphere and nearly absent for organisms inhabiting in both the Andean and the Extra-Andean Patagonia. In the present study we performed a wide range sampling covering almost the whole distribution range of Calceolaria polyrhiza (Calceolariaceae) and used sequence data from the chloroplast DNA psbA-trnH intergenic spacer to obtain information on the phylogeographic pattern among 591 individuals from 68 populations. We used spatial genetic analyses to interpret phylogeographic patterns in the light of past climatic changes. The phylogeographic structure of C. polyrhiza reveals a complex evolutionary history composed of four geographically structured phylogroups showing distinct evolutionary pathways. Within the two southernmost distributed phylogroups a longitudinal phylogeographic structure is evident. For some clades retrieved, the divergence time estimates suggests recent diversification associated with the Greatest Patagonian Glacial (1 Ma), while, in some cases older phenomena, that occurred in the late Miocene and Pliocene, have to be invoked such as marine introgressions and vulcanisms. Overall our results are consistent with a scenario of multiple periglacial Pleistocene refugia and subsequent post-glacial population expansion to the Andes flanks. The influence of the Arid Diagonal in the genetic patterns is also discussed. Results also indicated in situ survival at the coast of central and southeastern Patagonia.