Temporal changes in population genetics of six threatened Brazilian plant species in a fragmented landscape

Abstract

Anthropic pressure has caused several changes in the environment, such as habitat loss and fragmentation. One effective way to evaluate its effects on population genetics is to monitor populations through time. We aimed to characterize the population genetics of six plant species at two different times (cohorts). We asked (1) if populations show genetic divergence between cohorts, (2) if any significant changes are present between the genetic index of cohorts and, if so, (3) whether such changes are related to the adult cohort fixation index. To address these questions, we studied 61 populations of 50 adult and 50 seedling individuals genotyped with allozyme markers. We calculated allelic richness (Ar), observed (Ho) and expected heterozygosity (He), and fixation index (f) for each population cohort; and pairwise FST between cohorts. Seedlings were genetically similar to the adults (mean pairwise FST = 0.014). No difference was found in the proportion of populations that showed increases and decreases of the genetic indexes over cohorts, except f, for which more populations showed a decrease. Adult fixation index had a correlation with Ho (r = 0.507, p = 3∙10−5) and He (r = −0.247, p = 0.055). A mean test between cohorts revealed the maintenance of high f values in Araucaria angustifolia and Ocotea catharinensis, as well as a significant decrease in He of Euterpe edulis, species widely explored in the past. Although we only studied two cohorts, general trends and significant changes were detected, which could be important in the conservation of those six species.