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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 (Fst = 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.

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In Brazil, Plectranthus species are known as "boldo" and have been used in popular medicine for analgesic and dyspeptic purposes. Plectranthus need to be well identified in order to be used as commercially genuine medicinal plants. Here we describe AFLP DNA patterns able to distinguish among different Pectranthus species. The genetic variability of P. grandis Cramer, P. barbatus Andr. and P. ornatus Codd was analyzed with two sets of AFLP primers allowing detection of 241 loci. A total of 22 monomorphic loci were identified in P. barbatus, 15 in P. grandis and 30 in P. ornatus. Among these, 5 loci were informative and species-specific to P. barbatus, 3 to P. grandis and 2 loci were unique to P. ornatus. The AFLP pattern analyzed by different clustering methods assembled individuals according to their species. So far, AFLP represents a genuine and strong method to certify medicinal plant materials.

Habitat fragmentation and a decrease in population size may lead to a loss in population genetic diversity. For the first time, the reduction in genetic diversity in the northernmost limit of natural occurence (southeastern Brazil) of Araucaria angustifolia in comparison with populations in the main area of the species continuous natural distribution (southern Brazil), was tested. The 673 AFLPs markers revealed a high level of genetic diversity for the species (Ht = 0.27), despite anthropogenic influence throughout the last century, and a decrease of H in isolated populations of southeastern Brazil (H = 0.16), thereby indicating the tendency for higher genetic diversity in remnant populations of continuous forests in southern Brazil, when compared to natural isolated populations in the southeastern region. A strong differentiation among southern and southeastern populations was detected (AMOVA variance ranged from 10%-15%). From Bayesian analysis, it is suggested that the nine populations tested form five “genetic clusters” (K = 5). Five of these populations, located in the northernmost limit of distribution of the species, represent three “genetic clusters”. These results are in agreement with the pattern of geographic distribution of the studied populations.