Euterpe precatoria is a Neotropical palm from South and Central America and is hyperdominant in Amazonia, where it is increasingly important in the Brazilian market for açaí. Genetic diversity, population structure and mating system of E. precatoria were characterized with 10 microsatellite markers in three localities (Codajás, Manacapuru, and Manaquiri) along the lower Solimões River, Amazonas, Brazil. Leaves of 63 mature palms were collected, as well as fruits from 30 of these to analyze 20 seedlings per progeny. Genetic differentiation across localities was substantial (GS′ = 0.304) for mature palms, suggesting that gene flow is restricted between localities due to isolation by distance. Inbreeding was significant in progenies from all populations (ranging from 0.059–0.076), but not for mature palms, suggesting selection for heterozygosity during maturation to the adult stage. The outcrossing rate was high (0.917–1.0), confirming that the species is predominantly allogamous. Matings were not random due to the occurrence of biparental inbreeding (0.021–0.079) and correlated matings (0.059–0.424), so open-pollinated progenies present mixtures of self-sibs, half-sibs, full-sibs, and self-half-sibs, resulting in mean effective population size within progenies (2.23–3.06) lower than expected for a random mating population. The mating system’s characteristics are those expected in a predominantly allogamous hyper-abundant palm and suggest that human management of these often-anthropogenic populations is unlikely to reduce genetic diversity in the short term if done in situ, as practiced by Indigenous Peoples and local communities. Intensification will require careful attention to maintain genetic diversity.
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