RESUMEN
Due to the nutritional content and commercial value of its seeds, Bertholletia excelsa is one of the most important species exploited in the Amazon region. The species is hermaphroditic, insect pollinated, and its seeds are dispersed by barochory and animals. Because the fruit set is dependent on natural pollinator activity, gene flow plays a key role in fruit production. However, to date, there have been no studies on pollen and seed flow in natural populations of B. excelsa. Herein, we used microsatellite loci and parentage analysis to investigate the spatial genetic structure (SGS), realized pollen and seed dispersal, and effective pollen dispersal for two B. excelsa populations in the Brazilian Amazon forest. Two plots were established in natural forests from which adults, juveniles, and seeds were sampled. Realized and effective pollen flow was greater than realized seed flow. The distance of realized pollen dispersal ranged from 36 to 2060 m, and the distance of realized seed dispersal ranged from 30 to 1742 m. Both pollen and seeds showed a dispersal pattern of isolation by distance, indicating a high frequency of mating among near-neighbor trees and seed dispersal near to mother trees. Both populations present SGS up to 175 m, which can be explained by isolation by distance pollen and seed dispersal patterns. Our results suggested that fragmentation of these forest populations may result in a significant decrease in gene flow, due to the isolation by distance pollen and seed dispersal patterns.
Asunto(s)
Bertholletia/genética , Polen/genética , Dispersión de Semillas , Semillas/genética , Bertholletia/fisiología , Bosques , Flujo Génico , Endogamia , Repeticiones de Microsatélite , Polen/fisiología , Aislamiento Reproductivo , Semillas/fisiologíaRESUMEN
In this study, we analyzed the genetic diversity and structure of remnants of mangaba populations in states of northeastern Brazil by applying 9 microsatellite markers previously developed to establish conservation strategies for germplasm and species preservation. Six to 20 individuals per population were analyzed, with a total of 94 individuals and 6 populations from the states of Ceará, Pernambuco, and Sergipe, Brazil. The intra-population positive fixation index (f) in all populations indicated inbreeding resulting from the lack of random mating. The mean genetic diversity index values GST, FST, and RST estimated for divergence among the 6 populations were 0.14 (P < 0.05), revealing moderate genetic differentiation. The smallest FST value (P ≥ 0.05) was observed between the Jacarecoara and Tapera populations (0.005) and the highest between the Barra dos Coqueiros and Jacarecoara populations (0.287). The Jacarecoara population was the most divergent among the populations analyzed. According to analysis of molecular variance results, the largest variation percentage resulted from variability within populations (83.18%). Bayesian clustering analysis showed the formation of 2 sets (K = 2). Our results are important for developing strategies for in situ conservation of the species, seed collection, and ex situ conservation. For both methods, conservation of the greatest possible genetic variability of the species is essential.