Data from: Genetic signature of adaptive peak shift in threespine stickleback

Transition of an evolving population to a new adaptive optimum is predicted to leave a signature in the distribution of effect sizes of fixed mutations. If they affect many traits (are pleiotropic), large effect mutations should contribute more when a population evolves to a farther adaptive peak than to a nearer peak. We tested this prediction in wild threespine stickleback fish (Gasterosteus aculeatus) by comparing the estimated frequency of large effect genetic changes underlying evolution as the same ancestor adapted to two lake types since the end of the ice age. A higher frequency of large effect genetic changes (quantitative trait loci) contributed to adaptive evolution in populations that adapted to lakes representing a more distant optimum than to lakes in which the optimum phenotype was nearer to the ancestral state. Our results also indicate that pleiotropy, not just optimum overshoot, contributes to this difference. These results suggest that a series of adaptive improvements to a new environment leaves a detectable mark in the genome of wild populations. Although not all assumptions of the theory are likely met in natural systems, the prediction may be robust enough to the complexities of natural environments to be useful when forecasting adaptive responses to large environmental changes.演化种群向新的自适应最优适应峰的转变过程，预计会在固定突变的效应量分布中留下特征信号。若突变影响多个性状（即具有多效性，pleiotropic），则当种群向更远的自适应最优适应峰演化时，大效应突变的贡献程度应当高于向更近的适应峰演化的情况。本研究以野生三棘刺鱼（Gasterosteus aculeatus）为研究对象，通过比较同一祖先自末次冰期结束以来，适应两类湖泊环境时其演化背后的大效应遗传变异（数量性状位点，quantitative trait loci）的估计频率，对上述预测进行了验证。相较于适应最优表型更接近祖先状态的湖泊种群，适应代表更远最优适应峰的湖泊种群，其自适应演化过程中贡献更大的大效应遗传变异的频率显著更高。本研究结果同时表明，正是多效性（pleiotropic）而非仅最优峰过冲（optimum overshoot）导致了这一差异。上述结果表明，针对新环境的一系列适应性改良过程，会在野生种群的基因组中留下可被检测到的分子标记。尽管该理论并非所有假设都能在自然系统中得到满足，但这一预测对于自然环境的复杂性具备足够的鲁棒性，可用于预测种群对大规模环境变化的自适应响应。