Positive correlation between vegetation dissimilarity and genetic differentiation of Carex sempervirens

Abstract

Synthesizing genetic data at population level and vegetation data at community level may give insight into how ecological and evolutionary processes associated with different vegetation influence genetic diversity and differentiation of plant populations. We correlated population genetic patterns of Carex sempervirens with community vegetation patterns in abandoned subalpine grassland in the Swiss Alps. Within-population genetic diversity (percentage of polymorphic bands and Nei's gene diversity) of C. sempervirens was not significantly correlated with plant richness, evenness or Shannon's diversity index (Pearson correlation coefficient | r|<0.32, P>0.10). However, the genetic distance ( F ST) between C. sempervirens populations was significantly positively correlated with the vegetation dissimilarity between communities (Mantel's r=0.23, P<0.01). The correlation between the population genetic differentiation and the vegetation dissimilarity was not due to the parallel effects of geographic isolation or site conditions, because F ST was not correlated with the geographic distance or the pairwise differences in any of the measured site condition parameters. One likely mechanism is that different plant communities were associated with different selective forces, which, in turn, influenced the genetic differentiation between C. sempervirens populations. Another possibility is that the vegetation heterogeneity (dissimilarity) generated ecological barriers against gene flow and thus enhanced the genetic differentiation between C. sempervirens populations.