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 four-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 colouration 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 wildtype 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，量化野生环境中基因型、表型与存活情况三者间的关联，始终是适应性研究的核心议题。我们开展了一项为期四年的标记重捕（capture-recapture）研究，在白沙生态交错带（ecotone，即白砂与暗色土壤生境的过渡区域）针对西南栅栏蜥（Sceloporus cowlesi），按基因型与表型分别测定其存活情况。本研究报告了三项始料未及的发现：其一，与此前研究揭示的沙丘核心区域的西南栅栏蜥的隐蔽性浅色体色与黑皮质素1受体基因（Mc1r）突变相关的结论相悖，生态交错带种群的体色表型与Mc1r基因型之间仅存在极微弱的关联；其二，生态交错带种群中衍生型Mc1r等位基因的频率随时间推移逐渐降低；其三，标记重捕数据显示，携带衍生型Mc1r等位基因的个体存活概率更低。据此，本研究结果表明，近年来生态交错带的自然选择可能更青睐野生型等位基因。即便在一个基因型与表型关联看似泾渭分明的研究系统中，我们的研究仍表明，表型可塑性（phenotypic plasticity）、上位性（epistasis）、多效性（pleiotropy）以及基因流（gene flow）等额外因素，在白沙生态交错带中可能发挥着重要作用。本研究凸显了整合分子、基因组与个体水平研究方法，以理解野外适应性演化的重要性。此外，我们的研究结果显示，自然选择的动态过程在生态交错带这类过渡生境中可能尤为复杂，并强调未来亟需开展更多研究，以探明其他生态“灰色地带”中持续进行的自然选择模式。