Analysis of the correlation between genetic and species diversity in a temperate forest: Variation in cohorts and effect of disturbance

Abstract

Species diversity and genetic diversity are related through three possible predictions: the parallel action of eco-evolutionary processes on the two diversity components; the influence of genetic diversity on species diversity; or vice versa. Environmental factors affect these relationships because they affect population size and migration. Since environmental changes have a late effect on genetic diversity in long-lived species, this study analyzed the relationship between species diversity and genetic diversity of two cohorts of Abies religiosa and Pinus montezumae in temperate forest tree assemblages and explored the effect of anthropogenic disturbance on this relationship. We expected to find positive correlations and an effect of species diversity on genetic diversity, relationships that become more intense under anthropogenic disturbance and in seedling populations. Twelve assemblages with evident deforestation were identified in La Malinche National Park; in each assemblage, disturbance was measured by the percentage of forest cover and the Disturbance Impact Factor. We estimated additive diversity and species turnover between pairs of assemblages while genetic diversity, differentiation, and distances were derived based on single-nucleotide polymorphisms. To test the first prediction, Spearman's correlations between species diversity and genetic diversity were performed, while the second and third predictions were assessed by constructing General Linear Models (GLMs). The influence of disturbance was evaluated using partial correlations and GLMs. In both species, positive correlations were identified that varied between cohorts, and disturbance had an interactive and additive influence on these relationships. In P. montezumae seedlings, species diversity affected genetic diversity, while we observed the opposite effect in adults. Furthermore, the genetic differentiation of A. religiosa seedlings was associated with environmental distances. Controlling land-use changes in temperate forests is a top priority for conserving species diversity and safeguarding genetic diversity and ecosystem functioning. This research contributes to understanding the eco-evolutionary processes that govern tree assemblages of temperate forests.