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，探究野生种群中基因型（genotype）、表型（phenotype）与生存状况之间的关联，始终是适应性演化研究的核心议题。本研究针对白沙生态交错带（白砂与黑土生境的过渡区域）内的西南侧斑鬣蜥（*Sceloporus cowlesi*）开展了为期四年的标记重捕研究，旨在明确不同基因型与表型个体的存活率差异。本研究报告了三项始料未及的发现：其一，过往研究显示，沙丘核心区域的西南侧斑鬣蜥所具有的隐蔽性白化体色，与黑皮质素1受体基因（melanocortin-1 receptor gene, Mc1r）的突变存在明确关联；但本研究发现，生态交错带内的该种群其体色表型与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（allele）的频率随时间推移逐渐下降。其三，标记重捕数据显示，携带衍生型Mc1r等位基因的西南侧斑鬣蜥个体存活率更低。据此，本研究结果表明，近年生态交错带的自然选择或许更倾向于野生型（wildtype）等位基因。即便在一个基因型-表型关联看似非黑即白的研究系统中，本研究仍揭示出，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，可能在白沙生态交错带中发挥关键作用。本研究凸显了整合分子、基因组与个体水平研究方法，以解析野生种群适应性演化机制的重要性。此外，本研究结果表明，自然选择的动态变化在生态交错带这类过渡生境中可能尤为复杂，同时强调未来亟需开展相关研究，以探究其他生态“灰色地带”内持续进行的自然选择模式。