Abstract
Andean orogenesis has driven the development of very high plant diversity in the Neotropics through its impact on landscape evolution and climate. The analysis of the intraspecific patterns of genetic structure in plants would permit inferring the effects of Andean uplift on the evolution and diversification of Neotropical flora. In this study, using microsatellite markers and Bayesian clustering analyses, we report the presence of four genetic clusters for the palm Oenocarpus bataua var. bataua which are located within four biogeographic regions in northwestern South America : (a) Chocó rain forest, (b) Amotape-Huancabamba Zone, (c) northwestern Amazonian rain forest, and (d) southwestern Amazonian rain forest. We hypothesize that these clusters developed following three genetic diversification events mainly promoted byAndean orogenic events. Additionally, the distinct current climate dynamics among northwestern and southwestern Amazonia may maintain the genetic diversification detected in the western Amazon basin. Genetic exchange was identified betweenthe clusters, including across the Andes region, discarding the possibility of any cluster to diversify as a distinct intraspecific variety. We identified a hot spot of geneticdiversity in the northern Peruvian Amazon around the locality of Iquitos. We alsodetected a decrease in diversity with distance from this area in westward and southward directionwithin theAmazon basin and the easternAndean foothills.Additionally,we confirmed the existence and divergence of O. bataua var. bataua from var. oligocarpus in northern South America, possibly expanding the distributional range of thelatter variety beyond eastern Venezuela, to the central and eastern Andean cordilleras of Colombia. Based on our results, we suggest that Andean orogenesis is themain driver of genetic structuring and diversification in O. bataua within northwestern South America.