When ecological adaptation matters: Nothofagus populations with concordant geographic patterns have conserved species’ identity in sympatry since the Paleogene

PREMOLI, A.C., P. MATHIASEN & M.C. ACOSTA

Congreso; Evolution 2010 Annual Meetings; 2010

• We performed phylogenetic analyses and estimated divergence times on mostly sympatric populations of five species within subgenus Nothofagus to investigate whether phylogeographic patterns mirror climatic oscillations of the Quaternary or palaeofeatures of the landscape. Almost all species pairs hybridize, have limited seed dispersal, and share a pollen type that was present in Patagonia since the Eocene. • Fifteen chloroplast DNA haplotypes resulted from the analysis of three non-coding regions on 330 individuals with a total alignment of 1,794 bp. We found a geographically concordant allopatric divergence of mid Tertiary age among populations of all five species at mid latitudes of Patagonia. Also, other genetic breaks occurred towards the north. • Complex paleogeographic features explain such genetic discontinuities that were probably reinforced by glaciations of the Neogene. Long-lasting palaeobasins and Pacific marine ingressions impeded transoceanic dispersal during range expansion towards lower latitudes under cooler trends of the Oligocene. • Under relaxed selection during colonization of new habitats, cycles of hybridization-introgression have resulted in widespread chloroplast capture events that favored long-distance pollen flow. Our data suggest that Nothofagus biogeography will be resolved only if thorough phylogeographic analyses and molecular dating methods are applied using distinct genetic markers.