Pleistocene refugia and recolonization routes in the southern Andes: insights from Hypochaeris palustris (Asteraceae, Lactuceae)

Hypochaeris palustris (Phil.) De Wild. is a species growing in the southern Andean chain. To elucidate potential Pleistocene refugia and recolonization routes in the southern Andes, we analysed amplified fragment length polymorphisms (AFLPs) in 206 individuals in 21 populations of H. palustris from the coastal Cordillera, the central, northern, and eastern ranges of the southern Andes, and Patagonia. Populations from the coastal Cordillera harboured more private AFLP fragments, and exhibited a higher frequency of polymorphic fragments as well as higher Shannon diversity than all other areas investigated. The comparison among pooled AFLP profiles of each region revealed that the central Andean ranges shared most fragments with populations from the margins of the distributional area in the Andes, in the N, E, and S (Patagonia). Phenetic analysis indicated close relationships among populations of the central ranges. Populations of the coastal Cordillera were shown to be highly differentiated from the Andean populations. It is very likely therefore that (1) H. palustris recolonized the central ranges of the southern Andes from nearby refugia, possibly unglaciated areas N, E, and/or S of its present distributional area; (2) the postglacial spread of H. palustris in the central ranges of the southern Andes occurred rapidly; and (3) the coastal Cordillera served as a refugium for H. palustris, but these populations did not contribute to the recolonization of the central Andean ranges.