Linking geological and biological evolution: phylogeographical evidence on Nothofagus reflects the complex paleogeography of Patagonia

PREMOLI, ANDREA C.; MATHIASEN, PAULA; ACOSTA, M. CRISTINA

San Carlos de Bariloche, Rio Negro, Argentina

Congreso; VI Southern Connection Congress; 2010

Distribution patterns of extant austral elements, although recognized to have links with Tertiaryevolution, have been mostly explained in relation to Neogene events. We tested the hypothesis that living species of subgenus Nothofagus, found at present as continuous populations in southern South America and a fossil record occurring in all southern lands, consists of ancient lineages. We predict that phylogeographic paterns will be congruent with paleogeographic features of austral land masses. We performed a detailed multi-species phylogeographic analysis using sequences of three chloroplast DNA non-coding regions on a total of c. 200 populations along entire ranges of the five extant species within subgenus Nothofagus which are thought to have endured ice ages in multiple local refugia and we dated the resulting intraspecific phylogenies. Our results show a major genetic discontinuity between populations of all five studied species at mid latitudes of Patagonia that occurred 40 Myr ago. We hypothesize that this allopatric divergence arose due to long-lasting paleobasins that impeded transoceanic dispersal. Also that land-based dispersal occurred using pre-Miocene mountains as corridors throughout at least two connections with Antarctica. We show the utility of phylogeographical reconstruction shedding light on complex paleogeographical features of Paleogene landscapes shaping the gene pool of ancient cold hardy species that were not reset by glaciations of the Neogene.