Climate Variables Explain Neutral and Adaptive Variation within Salmonid Metapopulations: the Importance of Replication in Landscape Genetics
Understanding how environmental variation inﬂuences population genetic structure is important for conservation management because it can reveal how human stressors inﬂuence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population-speciﬁc and pairwise FST) within ﬁve metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, USA. Using 151 putatively neutral and 29 candidate adaptive SNP loci, we found that climate-related variables (winter precipitation, summer maximum temperature, winter highest 5% ﬂow events and summer mean ﬂow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely inﬂuences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables and FST across all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin-wide to the metapopulation scale). Sensitivity analysis (leave-one-population-out) revealed consistent relationships between climate variables and FST within three metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (N = 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics
Hand, B.K., C.C. Muhlfeld, A.A. Wade, R.P. Kovach, D.C. Whited, S.R. Narum, A.P. Matala, M.W. Ackerman, B.A. Garner, J.S. Kimball, J.A. Stanford, and G.L. Luikart. 2016. Climate variables explain neutral and adaptive variation within salmonid metapopulations: the importance of replication in landscape genetics. Molecular Ecology 25(3):689-705. Online at https://doi.org/10.1111/mec.13517.