Andean orogenesis has driven the development of very high plant diversity in theNeotropics through its impact on landscape evolution and climate. The analysis ofthe intraspecific patterns of genetic structure in plants would permit inferring theeffects of Andean uplift on the evolution and diversification of Neotropical flora. Inthis study, using microsatellite markers and Bayesian clustering analyses, we reportthe presence of four genetic clusters for the palm Oenocarpus bataua var. batauawhich are located within four biogeographic regions in northwestern South America:(a) Chocó rain forest, (b) Amotape-Huancabamba Zone, (c) northwestern Amazonianrain forest, and (d) southwestern Amazonian rain forest. We hypothesize that theseclusters developed following three genetic diversification events mainly promoted byAndean orogenic events. Additionally, the distinct current climate dynamics amongnorthwestern and southwestern Amazonia may maintain the genetic diversificationdetected 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 direction within the Amazon basin and the eastern Andean 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.
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