Simulating the selfing and migration of Luehea divaricata populations in the Pampa biome to investigate the conservation potential of their genetic resources.

Computer simulations are an important tool for developing conservation strategies for forest species. This study used simulations to investigate the genetic, ecological, and reproductive patterns that contribute to the genetic structure of the tree Luehea divaricata Mart. & Zucc. in five forest fragments in the Brazilian Pampa biome. Using the EASYPOP model, we determined the selfing and migration rates that would match the corresponding genetic structure of microsatellite marker data (based on observed and expected heterozygosity parameters). The simulated reproductive mode was mixed, with a high rate of outcrossing (rate = 0.7). This was consistent with a selfing-incompatible system in this species, which reduced, but did not prevent, selfing. The simulated migration rate was 0.02, which implied that the forest fragments were isolated by distance, and that the inbreeding coefficients were high. Based on Nei's gene diversity analysis, 94% of the genetic variability was distributed within the forest fragments, and only 6% of the genetic diversity was caused by differences between them. Furthermore, the minimum viable population and minimum viable area genetic conservation parameters (which determine conservation potential in the short and long term) suggested that only the Inhatinhum forest fragment had the short-term potential to maintain its genetic diversity. However, in the long term, none of the forest fragments proved to be sustainable, indicating that the populations will require intervention to prevent a decline in genetic variability. The creation of ecological corridors could be a useful solution to connect forest fragments and enhance gene flow between them.

Study of the genetic diversity and structure of a natural population of Nectandra megapotamica (Spreng.) Mez. using RAPD markers.

Nectandra megapotamica (Spreng.) Mez. is a tree species that naturally occurs in the Atlantic Forest, Brazil. The aim of this study was to evaluate the genetic diversity and structure of a natural population of 12 N. megapotamica individuals using random amplified polymorphic DNA markers. Eleven primers were used in this study, producing 81 bands, of which 98.99% were polymorphic. Analysis using STRUCTURE defined three different clusters (K = 3), results that were consistent with those of principal coordinates analysis. Both Nei's genetic diversity (h = 0.33) and Shannon's diversity index (I = 0.49) were relatively high. Analysis of molecular variance indicated that 24.89% of the genetic variability was among clusters, while the remaining 75.11% was within clusters. The Mantel test showed a weak correlation between genetic and geographic distances (r = 0.25, P = 0.105). Overall, the results revealed high levels of genetic diversity within clusters and high genetic differentiation among clusters without any spatial pattern of genetic variability. In addition, gene flow was independent of the geographical distribution and was compatible with the hierarchical island model.