Even population differentiation for maternal and biparental gene markers in Eugenia uniflora, a widely distributed species from the Brazilian coastal Atlantic rain forest

Brazilian cherry (Eugenia uniflora L.) occurs in the Brazilian Atlantic Coastal Tropical Forest from the north-eastern state of Ceara, to the southernmost state of Rio Grande do Sul. E. uniflora plays an important role in the maintenance of 'Restinga' ecosystems, at the interface between forest and strand vegetation. Here, we characterize the genetic diversity, its allocation within and between populations and the possible components of nuclear and cytoplasmic gene flow that determine the spatial distribution of the genetic variability. Five E. uniflora populations encompassing distinct biogeographical components were sampled: populations at extremes of latitudinal distribution, at an oceanic island and close to the major urban centre of Rio de Janeiro. AFLP markers showed that genetic variance among studied populations was moderate (F-st = 0.211) with 78.9% of variability residing within populations. The estimated seed and pollen components of gene flow among populations were approximately equal, with a ratio between 1.003 and 0.713 in function of the cpDNA marker used. The five populations present a considerable genetic structure, as assigned by both nuclear and chloroplastic DNA markers. Our data suggest the existence of different glacial refugia and a limited pollen and seed gene flow, mainly between the southern and the other regions enclosed in the Atlantic rain forest. Therefore, any strategy of conservation and management has to assure the preservation of several populations along the Atlantic coast, to maintain the majority of the intra specific level of diversity.