Data from: Phenotypic integration in the feeding system of the eastern diamondback rattlesnake (Crotalus adamanteus)

Selection can vary geographically across environments and temporally over the lifetime of an individual. Unlike geographic contexts, where different selective regimes can act on different alleles, age-specific selection is constrained to act on the same genome by altering age-specific expression. Snake venoms are exceptional traits for studying ontogeny because toxin expression variation directly changes the phenotype; relative amounts of venom components determine, in part, venom efficacy. Phenotypic integration is the dependent relationship between different traits that collectively produce a complex phenotype and, in venomous snakes, may include traits as diverse as venom, head shape, and fang length. We examined the feeding system of the eastern diamondback rattlesnake (Crotalus adamanteus) across environments and over the lifetime of individuals and used a genotype-phenotype map approach, protein expression data, and morphological data to demonstrate that: (1) ontogenetic effects explained more of the variation in toxin expression variation than geographic effects, (2) both juveniles and adults varied geographically, (3) toxin expression variation was a result of directional selection, and (4) different venom phenotypes co-varied with morphological traits also associated with feeding in temporal (ontogenetic) and geographic (functional) contexts. These data are the first to demonstrate, to our knowledge, phenotypic integration between multiple morphological characters and a biochemical phenotype across populations and age classes. We identified copy number variation as the mechanism driving the difference in the venom phenotype associated with these morphological differences, and the parallel mitochondrial, venom, and morphological divergence between northern and southern clades suggests that each clade may warrant classification as a separate evolutionarily significant unit.选择作用可随环境差异呈现地理分化，也可随个体生命周期发生时序变化。与地理环境下不同选择模式（selective regimes）作用于不同等位基因的情况不同，年龄特异性选择需通过调控年龄特异性基因表达，作用于同一套基因组。蛇毒是研究个体发育（ontogeny）的绝佳模型性状，因为毒素表达差异可直接改变表型；毒液组分的相对丰度在一定程度上决定了毒液的生物效能。表型整合（phenotypic integration）指不同性状间的依赖关联，这些性状共同构成复杂表型；在有毒蛇类中，表型整合可涵盖毒液、头部形态、毒牙长度等多种性状。我们针对东部菱斑响尾蛇（Crotalus adamanteus）的取食系统开展了跨环境与全生命周期的研究，并结合基因型-表型图谱（genotype-phenotype map）分析方法、蛋白质表达数据与形态学数据，证实了以下结论：（1）个体发育效应对毒素表达变异的解释度高于地理效应；（2）幼体与成体均存在地理变异；（3）毒素表达变异由定向选择驱动；（4）不同毒液表型与取食相关的形态性状在时序（个体发育）与地理（功能）维度上均存在协同变异。据我们所知，本研究首次证实了不同种群与年龄组间，多种形态性状与生化表型之间存在表型整合现象。我们明确了拷贝数变异（copy number variation）是驱动上述毒液表型差异的分子机制，而北部与南部演化支之间在线粒体基因组、毒液特征与形态性状上的平行分化提示，每个演化支均可被归类为独立的进化显著单元（evolutionarily significant unit）。