Phylogeographic Patterns of Fragmentation and Expansion of the Endemic Perennial Legume Anarthrophyllum desideratum (DC) Benth. in Southern Patagonia.

WRIGHT A.B.; COSACOV A.; PAIARO V.; SÉRSIC A.N.; COCUCCI A.A.; JOHNSON L.A

Vancouver, Canadá

Congreso; Botany without Borders.; 2008

Canadian Botanical Association/Botanical Society of America y otros.

Genetic variation in Anarthrophyllum desideratum was investigated throughout its distribution in Southern Patagonia. Anarthrophyllum desideratum (Fabaceae, Papilionoideae) is a woody subshrub occurring as isolated, dense populations distributed throughout a broad climatic range. Samples were taken from sites in Argentina extending from 42º34’ to 51º56’ S and from 72º51’ to 66º46’ W, covering most of the species range. Chloroplast DNA sequences of the trnS-trnG intergenic spacer were obtained and analyzed from 200 individuals representing 25 localities. Nested clade phylogeographic analysis of the 32 haplotypes revealed two clades at the highest level, one mainly in the North and the other mainly in the South. At the next highest clade level, the northern group is separated into two distinct western and eastern groups. Patterns of variation in the western populations indicate past fragmentation probably due to climatic changes during Pleistocene glaciations. The eastern populations showed southern dispersion with restricted gene flow. These populations seem to be more stable in time because the only process inferred from them was restricted gene flow, a process that can be expected for this species due to the limited autochorous seed dispersion. The southern clade exhibited north-eastern range expansion, which likely has been modulated by climatic changes. The highest genetic variation was encountered in populations sampled near areas that were covered in ice, giving evidence of refuges at these latitudes. Only one of these populations was from an area previously covered by glaciers, indicating it was colonized from the nearby refuges after the glaciers receded. Future analysis with additional molecular markers will help to get a fine grain resolution of the complex genetic distribution pattern found in A. desideratum. We acknowledge NSF-PIRE award (OISE 0530267).