The S. adstringens, a typical Cerrado (Brazilian savannah) tree, is used because of its medicinal and tanning properties. Because of the still incipient genetic knowledge of the species, the objective of this work was to characterize the diversity and genetic structure of S. adstringens by using allozyme markers. Seeds were collected in five Brazilian mesoregions, in which 627 individuals in 16 populations in the states of Minas Gerais and Goiás were sampled. Fourteen isoenzyme systems were assessed, out of which seven were polymorphic with a total of 10 loci and 28 alleles. Average genetic diversity (H) was 0.226, average proportion of polymorphic loci (P) was 68.75, average number of alleles per polymorphic locus (AP) was 2.65 and effective number of alleles (Ae) was equal to 1.29. The results of total fixation index (F= 0.003), within population fixation index (f =-0.114) and genetic differentiation measure (θ =0.105) were not significant, which shows the inexistence of genetic structure. Two principal groups were found in the cluster analysis (UPGMA), where the first one was formed by the population of State Park (PE) of Rio Preto (MG) and the other, by the other populations. If the population of PE of Rio Preto is excluded from the analysis, G ST is drastically reduced from 0.077 to 0.026. Thus, approximately 2/3 of the total value of G ST found in S. adstringens was due to the variation among the population of PE of Rio Preto and the other populations. Overall, the values of H and P found in S. adstringens are compatible with the ones found in typically distributed tropical trees. On the other hand, by excluding the population of PE of Rio Preto, the value of the G ST genetic differentiation measure was smaller than the one found in native tropical trees from temperate zones. The similarity between the assessed populations shows that the gene flow is still high enough to avoid genetic differentiation, at the local level, at least.
allozyme loci; genetic diversity; "barbatimão"; medicinal plants
