Spatio - temporal influence of gene dispersal on genetic variability distribution: anadenanthera colubrina var. cebil (Leguminosae) as case of study

Abstract

The studies of gene dispersal allow to understand the biological processes underlying spatial genetic distribution. Limited gene dispersal in plants is strongly affected by both ecological and evolutionary processes in a spatio-temporal framework. Considering the influence of landscape configuration on gene dispersal from a spatial perspective, the fragmentation of continuous tree populations may lead to genetic erosion due to the effects of genetic drift, inbreeding, and restricted current gene flow among the remnant forest patches, whereas the historical gene flow by pollen and seeds is the responsible mechanisms of temporal dynamics of genetic variability distribution. In the present study, we evaluate the ecological and evolutionary consequences of gene dispersal on the distribution of genetic variability within and among populations of Anadenanthera colubrina var. cebil, a keystone legume tree from Seasonally Dry Tropical Forests.Individuals from several populations of Misiones and Subandean Piedmont nuclei of Seasonally Dry Tropical Forests were genotyped by means of microsatellite loci. First, spatial clustering, gene dispersal rates and sibship structures were determined over fine spatial scales to characterize the patterns of gene movement considering two life stages within populations from Misiones nucleus. Then, the extent of historical gene flow among populations from Misiones and Subandean Piedmont nuclei was estimated from the genetic structure degree to evaluate the role of fragmentation on genetic variability patterns over timescales. Also, the relative role of gene flow mediated by seeds and gene flow mediated by pollen and seeds was quantified.At local scale, sapling recruitment and genetic clustering were detected. They could be a consequence of limited mobility of propagules, restricted effective gene dispersal, mixed mating system with high frequency of self-pollination, and the establishment of clumped related saplings. Also, moderate genetic structure was detected which may be a consequence of recent fragmentation in modified environments by human activities. Hence, historical and demographic events increase the isolation of remnant patches and the effects of genetic drift. In this way, the dynamic integration of the species biology, spatial ecology, and historical demographic events provide valuable tools for a multi-scale understanding of gene dispersal processes and their consequences on genetic variability distribution.