Genetic diversity and structure of the tree Enterolobium contortisiliquum (Fabaceae) associated with remnants of a seasonallydry tropical forest.

Abstract

Fragmentation of tropical forests is one of the major threats to biodiversity and viable natural popu-lations. Brazilian seasonally dry tropical forests (SDTF) are endangered because of human occupation,conversion of lands to agriculture and high deforestation rates in these fertile soils. Enterolobium contor-tisiliquum has been removed from SDTF natural areas due to the advance of cattle grazing and agriculturein Brazilian SDTFs. To aid conservation efforts of this species we used molecular markers to study thegenetic diversity and population structure of E. contortisiliquum in Brazilian SDTF remnants. A total of263 individuals in 13 forest patches were analyzed with 103 ISSR fragments. In spite of being found scat-tered among the SDTF patches, E. contortisiliquum populations exhibited high genetic diversity (meanShannon’s index of diversity = 0.384; mean genetic diversity = 0.280) and genetic divergence betweenpopulations was detected (˚ST= 0.155, p < 0.0001). UPGMA dendrogram, principal coordinate analysisand Bayesian analysis showed that E. contortisiliquum populations were clustered into three groups thatwere not related to geographic distance (r = 0.119, p = 0.197). However, these populations are spatiallystructured into groups distributed in the West, Central and East of the study area. This genetic structuremay be related with landscape and both the Espinhac¸ o Range and São Francisco River may act as a par-tial geographic barrier limiting the gene flow. Because the highest rates of genetic diversity were foundoutside of conservation units, we propose the creation of protected areas in different geographic regionsthat include E. contortisiliquum populations from different genetic clusters