Habitat fragmentation decreased the genetic variability of Trichilia elegans A. Juss. (Meliaceae) in southern Brazil

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.