Data from: Survival by genotype: patterns at Mc1r are not black and white at the White Sands ecotone

Measuring links among genotype, phenotype and survival in the wild has long been a focus of studies of adaptation. We conducted a 4-year capture–recapture study to measure survival by genotype and phenotype in the Southwestern Fence Lizard (Sceloporus cowlesi) at the White Sands ecotone (transition area between white sands and dark soil habitats). We report several unanticipated findings. First, in contrast with previous work showing that cryptic blanched coloration in S. cowlesi from the heart of the dunes is associated with mutations in the melanocortin-1 receptor gene (Mc1r), ecotonal S. cowlesi showed minimal association between colour phenotype and Mc1r genotype. Second, the frequency of the derived Mc1r allele in ecotonal S. cowlesi appeared to decrease over time. Third, our capture–recapture data revealed a lower survival rate for S. cowlesi individuals with the derived Mc1r allele. Thus, our results suggest that selection at the ecotone may have favoured the wild-type allele in recent years. Even in a system where a genotype–phenotype association appeared to be black and white, our study suggests that additional factors – including phenotypic plasticity, epistasis, pleiotropy and gene flow – may play important roles at the White Sands ecotone. Our study highlights the importance of linking molecular, genomic and organismal approaches for understanding adaptation in the wild. Furthermore, our findings indicate that dynamics of natural selection can be particularly complex in transitional habitats like ecotones and emphasize the need for future research that examines the patterns of ongoing selection in other ecological 'grey' zones.

长期以来，探究野生种群中基因型、表型与存活间的关联，一直是适应性研究的核心议题。本研究针对白沙生态交错带（白沙地与深色土壤生境的过渡区域）的西南栅栏蜥（*Sceloporus cowlesi*）开展了为期4年的标记重捕研究，按基因型与表型分类统计其存活情况，并得到若干意料之外的发现：其一，既往研究表明，沙丘核心区的西南栅栏蜥其隐蔽性白化体色与黑皮质素-1受体基因（melanocortin-1 receptor gene, Mc1r）的突变存在关联，但本研究中生态交错带的西南栅栏蜥，其体色表型与Mc1r基因型间的关联极弱；其二，生态交错带西南栅栏蜥中衍生型Mc1r等位基因的频率随时间推移呈下降趋势；其三，标记重捕数据显示，携带衍生型Mc1r等位基因的西南栅栏蜥个体存活率更低。综上，本研究结果表明，近年来生态交错带的自然选择可能更倾向于野生型等位基因。即便在基因型与表型关联看似泾渭分明的研究系统中，本研究仍表明，表型可塑性、上位性、多效性及基因流等额外因素，在白沙生态交错带中可能发挥着重要作用。本研究强调，将分子、基因组及个体水平的研究方法相结合，对于理解野生种群的适应性演化至关重要。此外，本研究结果显示，自然选择的动态在生态交错带等过渡生境中往往尤为复杂，这也强调了未来需开展相关研究，以探究其他生态“灰色地带”中持续进行的自然选择模式。