Phylogeographically concordant chloroplast DNA divergence in sympatric Nothofagus s.s. How deep can it be?

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

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011

0028-646X

• We performed phylogenetic analyses and estimated divergence times on mostly sympatric populations of five species within subgenus Nothofagus. We aim to investigate whether phylogenetic relationships by nuclear ITS and phylogeographic patterns by cpDNA mirror an ancient evolutionary history that was not erased by glacial eras. Extant species are restricted to Patagonia and share a pollen type that was formerly widespread in all southern land masses. Weak reproductive barriers exist among them. • Fifteen chloroplast DNA haplotypes resulted from the analysis of three non-coding regions on 330 individuals with a total alignment of 1,794 bp. Nuclear ITS data consisted of 822 bp. We found a deep cpDNA divergence at mid latitudes of Patagonia that predates phylogenetic divergence of extant taxa. Other more recent breaks by cpDNA occurred towards the north. • Complex paleogeographic features explain genetic discontinuities. Long-lasting palaeobasins and marine ingressions impeded transoceanic dispersal during range expansion towards lower latitudes under cooler trends of the Oligocene. • Cycles of hybridization-introgression among extant and extinct taxa have resulted in widespread chloroplast capture events. Our data suggest that Nothofagus biogeography will be resolved only if thorough phylogeographic analyses and molecular dating methods are applied using distinct genetic markers.