Environmental effects, gene flow and genetic drift: Unequal influences on genetic structure across landscapes

Abstract

AbstractAimBoth gene flow and genetic drift can affect the genetic diversity of interacting populations. However, the influence of the complex evolutionary histories of species may be obscured by simplified assumptions about how these roles operate in nature. To examine this issue, we mechanistically explored the relative importance of environment‐mediated gene flow and genetic drift in determining genetic structure and diversity.LocationNortheast Japan.TaxonCaddisflies (Hydropsyche orientalis and Stenopsyche marmorata; Insecta: Trichoptera).MethodsWe developed a novel Bayesian framework to evaluate the individual and joint effects of these two evolutionary processes that operate through environmental networks on genetic structuring of these populations. Modelling was performed using genetic information on the two sympatric species of stream—macroinvertebrates having aerial‐dispersing adult stages. Genotyping data for samples from 41 and 30 locations were used at 98 and 162 neutral amplified fragment length polymorphism loci in H. orientalis and S. marmorata, respectively.ResultsEnvironmental conditions and habitat quality can mediate gene flow by providing different levels of resistance to interpopulation dispersal. Similarly, genetic drift may be altered through variable environmental limitations on population size. Compared to the role of genetic drift, gene flow has a greater influence on the genetic diversity of both species examined. The elevated gene‐flow levels generally increase the genetic diversity in S. marmorata, whereas no obvious trend is evident across the various degrees of gene flow in H. orientalis.Main ConclusionsInformation on environmentally mediated gene flow and genetic drift, coupled with different dispersal strategies in habitat networks, may influence management efforts and success. Consequently, evolutionary processes that act individually or jointly in determining genetic structure are important in the effectiveness of management strategies used for restoration and conservation efforts.