Data from: Laboratory selection quickly erases historical differentiation

The roles of history, chance and selection have long been debated in evolutionary biology. Though uniform selection is expected to lead to convergent evolution between populations, contrasting histories and chance events might prevent them from attaining the same adaptive state, rendering evolution somewhat unpredictable. The predictability of evolution has been supported by several studies documenting repeatable adaptive radiations and convergence in both nature and laboratory. However, other studies suggest divergence among populations adapting to the same environment. Despite the relevance of this issue, empirical data is lacking for real-time adaptation of sexual populations with deeply divergent histories and ample standing genetic variation across fitness-related traits. Here we analyse the real-time evolutionary dynamics of Drosophila subobscura populations, previously differentiated along the European cline, when colonizing a new common environment. By analysing several life-history, physiological and morphological traits, we show that populations quickly converge to the same adaptive state through different evolutionary paths. In contrast with other studies, all analysed traits fully converged regardless of their association with fitness. Selection was able to erase the signature of history in highly differentiated populations after just a short number of generations, leading to consistent patterns of convergent evolution.进化历史、随机偶然性与自然选择在进化生物学（evolutionary biology）中的作用长期以来备受学界争论。尽管均匀选择（uniform selection）理论上会导致不同种群间出现趋同进化（convergent evolution），但迥异的进化历史与随机事件可能会阻碍种群达成一致的适应状态（adaptive state），进而令进化过程具备一定的不可预测性。已有多项研究通过记录自然与实验室环境中可重复的适应辐射（adaptive radiations）与趋同现象，为进化的可预测性提供了支撑。不过另有研究表明，即便在相同环境下适应的种群间仍会出现分化。尽管该议题具备重要研究价值，但针对进化历史差异显著、且在适合度相关性状（fitness-related traits）上拥有充足现有遗传变异（standing genetic variation）的有性生殖种群（sexual populations）的实时适应（real-time adaptation）的实证数据仍较为匮乏。本研究针对曾沿欧洲渐变群（European cline）发生分化的暗果蝇（Drosophila subobscura）种群，分析其在定殖于全新统一环境时的实时进化动态（evolutionary dynamics）。通过对多项生活史性状（life-history traits）、生理性状（physiological traits）与形态性状（morphological traits）进行分析，本研究发现种群可通过不同的进化路径（evolutionary paths）快速趋同至一致的适应状态。与其他研究不同的是，本研究中所有被分析的性状均实现了完全趋同，无论其是否与适合度相关。仅经过短短数代繁衍，自然选择即可消除高度分化种群（highly differentiated populations）中的历史遗留信号，进而形成稳定一致的趋同进化模式。