Genetic structure of the Atlantic Rainforest tree species Luehea divaricata (Malvaceae).

The Atlantic Rain Forest is one of the most important Brazilian biomes and a hotspot for biodiversity that is characterized by its high level of endemism, where new species are still being described. Luehea divaricata (Malvaceae) is commonly found in riparian forests areas of the Atlantic forest. Because of the importance of this species in reforestation programs, we used nine pairs of microsatellite loci to study the genetic variability of this species along its distribution area and verify if fragmentation is compromising the survival of these populations. A total of 50 alleles were obtained with an average observed and expected heterozygosity of 0.53 and 0.67, respectively. Seven of the nine populations studied showed a heterozygosity deficit. Most of the genetic diversity was found within populations; while the level of genetic differentiation was moderated (6.84) between populations. Different levels of gene flow between the populations were detected. Positive and significant values of Fis were found for seven populations. The signal test for excess of heterozygosity indicated that a recent genetic bottleneck occurred in the fragmented populations. The dendrogram constructed by the UPGMA method revealed the formation of seven clusters, which was confirmed by the Bayesian analysis for number of K clusters. The presence of several pairs of loci in linkage disequilibrium confirms that these populations experienced a loss of genetic diversity caused by genetic drift. The results showed that it is necessary to develop management strategies for the conservation of these populations of L. divaricata as the viability of the next generations are severely compromised.