Jakob, Sabine S. , Martinez-Meyer, Enrique , Blattner, Frank R. .
Surviving the Pleistocene in situ: phylogeographic analysis and paleodistributional niche modeling of diploid Patagonian Hordeum species (Poaceae).
In southern Patagonia three diploid Hordeum species occur, which form a monophyletic group within the genus. Although they are mostly sympatric, their habitats are ecologically differentiated on a local scale. These species evolved during the last 1.3 million years from a common ancestor, thus providing an excellent system to study speciation processes in a young radiation. Phylogeographic analyses using chloroplast trnL-F sequences as well as modeling of present and Pleistocene climatic niches of the species were conducted to analyze the species‘ evolutionary history. Phylogeography infers at least one major vicariance event, separating one of the later three species from the last common ancestor of the remaining two. However, the phylogeographic analysis did not allow the clear definition of potential ice age refuges. In fact the observed haplotype patterns indicate that quite large populations survived the ice ages. These findings were strongly supported by models of the recent and Pleistocene species‘ distribution, which suggested the occurrence of Hordeum in situ even during the last glacial maximum about 18,000 years ago. Combining the complementary results of phylogeography and paleodistribution models offered clear insights into the evolutionary history of the species. Although they occur today in sympatry and are adapted to distinct ecological niches on a local scale, the analysis shows that this differentiation was not the reason for speciation, but evolved in allopatry after the species became reproductively isolated by geological barriers. The nature of these barriers is, however, currently unclear, as the Patagonian steppe east of the Andes was probably never completely fragmented by glaciers stretching from the Andes to the Atlantic Ocean.
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1 - Inst. of Plant Genetics and Crop Plant Research, Dept. of Taxonomy, Corrensstr. 3, Gatersleben, D-06466, Germany
2 - Universidad Nacional Autonoma de Mexico, Instituto de Biologia, Mexico City, 04510, Mexico
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 28th, 2008
Time: 3:45 PM