Spatial Genetic Structure, Genetic Diversity and Pollen Dispersal in a Natural Population of Astrocaryum aculeatum in Brazilian Amazonia

Astrocaryum aculeatum is widely appreciated in the Amazon where the pulp extracted from the fruits is consumed fresh and its production is almost exclusively made by extractive farmers. The aim of this research was to compare the genetic diversity between adult individuals and open-pollinated seeds, quantify pollen flow and dispersion, the spatial genetic structure, and the effective population size in a population subjected to fruit harvesting using 12 microsatellite loci. The study was carried out in a natural A. aculeatum population of approximately 8 ha and separated by 400 m from the nearest population in the State of Amazonas, Brazil. In this natural population we mapped 112 possible pollen donors, 12 mother plants and 120 offspring. Genetic diversity was high for both the parents and the offspring. The fixation indexes for adults (F = -0.035) and offspring (F = -0.060) were negative and not significant. A significant spatial genetic structure for the adult plants was detected up to the distance of 45 m, indicating short-distance seed dispersal. Paternity analysis detected 9.2% of pollen immigration and the average distance of pollination within the population was 81 m. The average effective pollination neighborhood area between plants was 1.51 ha. Our results indicate substantial input of alleles in the population through pollen immigration, contributing to the maintenance of genetic diversity, even when submitted to seed harvesting. The renovation with new selected offspring should be made from a minimum spacing of 50 m between mother plants to prevent collecting seeds from plant relatives.