The Atlantic-Mediterranean watershed, river basins and glacial history shape the genetic structure of Iberian poplars

Recent phylogeographic studies in several organisms have elucidated the varied effects of Pleistocene glaciations and of Pre-Pleistocene events on populations from glacial refuge areas. This study investigates those effects in riparian trees (Populus spp.), whose particular features may convey enhanced resistance to climate fluctuations. We analysed the phylogeographic structure of white, black and grey poplars (44, 13 and two populations, respectively) in the Iberian Peninsula using plasmid DNA microsatellites and sequences, we assessed fine-scale spatial genetic structure and the extent of clonality in four white and one grey poplar populations using nuclear microsatellites and we determined quantitative genetic differentiation (Q_ST) for growth traits among populations and river systems in white poplar. Black poplar displayed higher regional diversity and lower differentiation than white poplar, reflecting its higher cold-tolerance. In white poplar, the Atlantic and Mediterranean dra...