Phylogeographically concordant intraspecific cpDNA divergence in sympatric Nothofagus. How deep can it be?.

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

NEW PHYTOLOGIST

WILEY-BLACKWELL PUBLISHING, INC

Año: 2012 vol. 193 p. 261 - 275

0028-646X

- Here, we performed phylogenetic analyses and estimated the divergence timeson mostly sympatric populations of five species within subgenus Nothofagus. Weaimed to investigate whether phylogenetic relationships by nuclear internal transcribedspacer (ITS) and phylogeographic patterns by chloroplast DNA (cpDNA)mirror an ancient evolutionary history that was not erased by glacial eras. Extantspecies are restricted to Patagonia and share a pollen type that was formerly widespreadin all southern land masses. Weak reproductive barriers exist among them.- Fifteen cpDNA haplotypes resulted from the analysis of three noncoding regionson 330 individuals with a total alignment of 1794 bp. Nuclear ITS data consisted of822 bp. We found a deep cpDNA divergence dated 32 Ma at mid-latitudes ofPatagonia that predates the phylogenetic divergence of extant taxa. Other morerecent breaks by cpDNA occurred towards the north.- Complex paleogeographic features explain the genetic discontinuities. Longlastingpaleobasins and marine ingressions have impeded transoceanic dispersalduring range expansion towards lower latitudes under cooler trends since theOligocene.- Cycles of hybridization–introgression among extant and extinct taxa have resultedin widespread chloroplast capture events. Our data suggest that Nothofagusbiogeography will be resolved only if thorough phylogeographic analyses andmolecular dating methods are applied using distinct genetic markers.