Genetic variability of Eugenia uniflora L. in forest remnants at different successional stagesKnowledge on genetic diversity provides basic information about population dynamics and functioning aiming both to conservation and sustainable use of species. It is assumed that early successional populations could genetically be more differentiated than those in late sucessional stages. To test this hypothesis, the genetic variability of Eugenia uniflora L. populations at different successional stages was investigated. Two areas at different successional stages were selected; one at early successional stage, showing several pioneer trees, and another at late successional stage. The area in study (27°54'S and 52°13'W) is covered by a remnant forest in transition from Mixed Rain Forest to Recebido para publicação em 12/06/2012 e aprovado em 08/02/2013 1 Este trabalho é parte da dissertação de mestrado do primeiro autor.

The genus of Oligoryzomys includes species of small size, morphologically similar, which may impede taxonomic identification, mainly between O. flavescens (Waterhouse, 1837) and O. nigripes (Olfers, 1818). The main objective of this work was to investigate whether the RAPD markers are capable of genetically differentiating the specimens O. nigripes and O. flavescens, coming from Rio Grande do Sul (RS) and Santa Catarina (SC) states, and also to estimate the genetic variability among populations of O. nigripes, with the Uruguay River as a geographical barrier. For this purpose, samples were collected in fragments of forests situated in the North of RS, at FLONA (Floresta Nacional de Passo Fundo) and in fragments from SC, close to the Uruguay River. The karyotyping of two samples for each species was carried out and compared using the RAPD technique together with non-karyotyped individuals. Samples of O. nigripes presented 2n = 62; NA = 82, with submetacentric arms on the largest chromosomes, while samples of O. flavescens showed 2n = 64; NA = 66, with the largest chromosomes presenting acrocentric morphology, making such a result the main difference between the species. The analysis was able to detect two distinct groups, being the first one with karyotyped O. flavescens and the second with karyotyped O. nigripes. Identification afforded 211 loci, among them 181 (85.78%) polymorphic. The Jaccard similarity coefficient was in the range of 0.45 to 0.87. The UPGMA and Main Coordinate Analysis techniques demonstrated the existence of heterogeneous genetics among populations, but did not separate them completely in terms of geographical standards, and they are not influenced by the Uruguay River, which did not act as an efficient barrier. Keywords

Habitat fragmentation and the creation of so-called edge effects may have different implications on flora and fauna, including complex genetic responses. This study aimed to analyze the genetic diversity in a local population of the shade tolerant tree Trichilia elegans A. Juss (Meliaceae), with emphasis to the evaluation of genetic variation towards an edge-interior gradient. The results of isoenzymes assays showed that the edge subpopulation experienced the highest allele loss, while fixed alleles increased towards the interior. The total polymorphic loci percentage was 76.67 %, being higher in the Middle subpopulation, whilethe average sample size for a locus (N) and the mean number of alleles for a locus (N a ) were significantly lower in the Edge subpopulation. The indices H o , H e and f showed good heterozygosity in the total population, indicating high genetic variability. The genetic distance Fs t and Nm followed the same pattern, with Middle and Interior subpopulations showing higher similarity and the Edge as the farthest one, also showing less gene flow in relation to the others. Principal Coordinates Analysis (PCoA) allowed us to separate the three subpopulations with the first two axes explaining 65% of total variation, confirming that forest fragmentation affects the genetics of Trichilia elegans within the analyzed fragment.