Theories predict that directional selection during adaptation to a novel habitat results in elevated meiotic recombination rate. Yet the lack of population-level recombination rate data leaves this hypothesis untested in natural populations. Here we examine the population-level recombination rate variation in two incipient ecological species, the microcrustacean Daphnia pulex (an ephemeral-pond species) and D. pulicaria (a permanent-lake species). The divergence of D. pulicaria from D. pulex involved habitat shifts from pond to lake habitats as well as strong local adaptation due to directional selection. Using a novel single-sperm genotyping approach, we estimated the male-specific recombination rate of two linkage groups in multiple populations of each species in common garden experiments and identified a significantly elevated recombination rate in D. pulicaria. Most importantly, population genetic analyses show that the divergence in recombination rate between these two species is most likely due to divergent selection in distinct ecological habitats rather than neutral evolution.

中文翻译：

---

生态物种形成中减数分裂重组率的适应性发散。

理论预测，在适应新栖息地期间的定向选择会导致减数分裂重组率升高。然而，由于缺乏种群水平的重组率数据，这一假设在自然种群中未经检验。在这里，我们研究了两种早期生态物种，即微甲壳动物Daphnia pulex（一种短暂的池塘物种）和D. pulicaria（一种永久性湖泊物种）的种群水平重组率变化。D. pulicaria与D. pulex的分化涉及栖息地从池塘到湖泊栖息地的转变以及由于定向选择而产生的强烈的当地适应性。我们使用一种新的单精子基因分型方法，在普通花园实验中估计了每个物种多个种群中两个连锁群的雄性特异性重组率，并确定了D. pulicaria 的重组率显着提高。最重要的是，种群遗传分析表明，这两个物种之间重组率的差异很可能是由于不同生态栖息地的不同选择，而不是中性进化。