Nuclear and chloroplast microsatellites reveal high genetic diversity and structure in Platonia insignis Mart., an endangered species native to the Brazilian Amazon

Bacurizeiro (Platonia insignis) is a fruit of the Amazon that, due to anthropic actions, has been suffering serious damage to its genetic diversity. We analyzed the genetic diversity and structure of seven bacurizeiro populations distributed among four Brazilian states and two biomes, the Amazon and Cerrado, based on eight nuclear (ncSSR) and three chloroplast (cpSSR) microsatellite markers. Higher heterozygosity values were found for the Northern populations of Japura and Marapanim, and the Northeast population of Chapadinha when using ncSSR. Higher diversity indices were also observed for these populations with cpSSR, although higher haplotypic diversity parameters were detected for the two Northern populations. Genetic structure analysis showed the formation of two well defined groups: I -populations from Maranhao and Piaui (Cerrado) and II - populations from Amazonas and Para (Amazon). Positive and significant correlations were identified between genetic and geographical distances for both ncSSR (r = 0.09; p = 0.0010) and cpSSR (r = 0.11; p = 0.0008), in agreement with the genetic structure analysis. The high genetic structure among populations probably reflects the divergent natural and human selection pressures to which bacurizeiros are subjected in both the Amazon and Cerrado biomes, with higher diversity maintained in the Amazon populations.