Functional genetic differentiation in environmentally marginal areas: hypothesis generation based on ecological niche models and tests with phenotypic data

Environmental variation within a species’ range may create contrasting selective pressures, leading to divergent selection and novel adaptations in various populations. Here, we explored the potential of ecological niche models (ENMs) coupled with common-garden experiments to identify environmentally contrasting areas inside a species’ range, hypothesize putative selective pressures, and test whether populations inhabiting stressful areas have predicted differentiated phenotypes. We built an ENM for the alpine plant Silene ciliata and then conducted common-garden experiments assessing flowering time and cell resistance to extreme temperatures. The ENM’s suitability patterns and response curves led to the hypothesis that populations experiencing less snowpack and higher minimum annual temperatures would have delayed flowering. The common-garden experiments revealed genetically-based phenological differentiation among populations concordant with these hypotheses. Results supported ENMs as useful hypothesis generators for studying selection in populations inhabiting environmentally contrasting areas.