Reproductive isolation can result from adaptive processes (e.g., ecological speciation and mutation-order speciation) or stochastic processes such as “system drift” model. Ecological speciation predicts barriers to gene flow between populations from different environments, but not among replicate populations from the same environment. In contrast, reproductive isolation among populations independently adapted to the same/similar environment can arise from both mutation-order speciation or system drift. In experimentally evolved populations adapting to a hot environment for over 100 generations, we find evidence for pre- and postmating reproductive isolation. On one hand, an altered lipid metabolism and cuticular hydrocarbon composition pointed to possible premating barriers between the ancestral and replicate evolved populations. On the other hand, the pronounced gene expression differences in male reproductive genes may underlie the postmating isolation among replicate evolved populations adapting to the same environment with the same standing genetic variation. Our study confirms that replicated evolution experiments provide valuable insights into the mechanisms of speciation. The rapid emergence of the premating reproductive isolation during temperature adaptation showcases incipient ecological speciation. The potential evidence of postmating reproductive isolation among replicates gave rise to two hypotheses: (1) mutation-order speciation through a common selection on early fecundity leading to an inherent inter-locus sexual conflict; (2) system drift with genetic drift along the neutral ridges.

中文翻译：

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实验室适应新的热环境期间出现生殖隔离


生殖隔离可能是由适应性过程（例如，生态物种形成和突变顺序物种形成）或随机过程（例如“系统漂移”模型）引起的。生态物种形成预测了来自不同环境的种群之间的基因流动障碍，但不能预测来自同一环境的复制种群之间的基因流动障碍。相反，独立适应相同/相似环境的种群之间的生殖隔离可能是由突变顺序物种形成或系统漂移引起的。在经过 100 代以上适应炎热环境的实验进化种群中，我们发现了交配前和交配后生殖隔离的证据。一方面，脂质代谢和表皮碳氢化合物成分的改变表明祖先群体和复制进化群体之间可能存在交配前障碍。另一方面，雄性生殖基因中显着的基因表达差异可能是适应具有相同遗传变异的相同环境的复制进化群体之间交配后隔离的基础。我们的研究证实，重复进化实验为物种形成机制提供了有价值的见解。温度适应过程中交配前生殖隔离的迅速出现展示了早期的生态物种形成。重复中交配后生殖隔离的潜在证据产生了两个假设：（1）通过对早期繁殖力的共同选择导致固有的位点间性冲突的突变顺序物种形成； (2)系统漂移与遗传漂移沿着中性脊线。