Weak relationship between neutral genetic diversity and demography in a plant at continental scale

Abstract

Population performance is determinant for the abundance and distribution of species and identifying the causes of its variation allows a better management of biodiversity. Besides the effect of environmental conditions, genetic diversity may also have significant demographic consequences, but there is greater knowledge of such effects in threatened species than in common organisms. In the present study, the influence of environmental conditions on the demography of a widespread herbaceous plant, Plantago coronopus, was analyzed throughout its European latitudinal range, considering also differences in neutral genetic diversity. Genetic diversity was only related to one of the demographic parameters analyzed, individual growth, and showed no influence on the population growth rate. In contrast, several abiotic (climate, soil) and biotic (population density) environmental factors had a greater influence on the life cycle components (survival, growth, reproduction). These individual rates showed opposite responses to environmental factors, a phenomenon known as demographic compensation, which resulted in an absence of pattern in the population growth rate along the environmental gradient. Our results highlight the importance of considering multiple individual and population demographic parameters to evaluate the relationship between a species genetics, environmental conditions, and demography. This study also suggests that, in organisms with wider distribution ranges, genetic factors may be less useful than environmental variables to predict population trends and future distribution in new ecological scenarios.