Experimental speciation: reinforcement in Drosophila melanogaster

物种形成发生在种群进化出繁殖障碍时。了解这些障碍是如何形成的是进化生物学的一个长期挑战。这是因为经常性移徙预计会消除人口之间任何新出现的差异。完成物种形成的一种方法是通过一个叫做强化的过程。强化发生在自然选择有利于避免杂交时，杂交后代是不太适合。这个项目使用实验进化研究进化的变化，因为它发生，以跟踪随着时间的推移种群之间的生殖障碍。这项工作将研究种群之间相对较弱的繁殖障碍是否会随着时间的推移而加强或减弱。利用这些数据，研究人员将确定强化可能发生的情况。作为该项目的一部分，高中，本科和研究生水平的学生将接受科学教育和培训。在当地一所中学和童子军中开展的一项推广计划将增加对遗传学的了解，并促进代表性不足的群体对科学的兴趣。支持和反对生殖隔离进化的证据主要来自自然种群的比较方法和快照研究。然而，这些方法往往遇到困难时，试图归因于特定的进化力量的生殖隔离模式。这个项目将直接测试强化选择可以压倒基因流动的反作用力的假设。为了验证这一假设，这项工作将遵循果蝇种群中生殖隔离的进化，这些种群显示出一定程度的初始生殖隔离。一些实验种群将保持异地分布，而另一些将经历基因流动。在这些群体中，将操纵针对杂交的选择强度。对这些群体的竞争性和非竞争性生殖隔离的时间序列测量将揭示三个问题的答案。第一，强化能够加强生殖隔离的频率和一致性如何？第二，要发生这种情况，对杂交种的选择必须有多强？第三，是交配前（性）或交配后前合子（配子）隔离更进化不稳定？该项目由进化过程和刺激竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Speciation occurs when populations evolve barriers to reproduction. Understanding how these barriers form is a longstanding challenge in evolutionary biology. This is because recurrent migration is expected to erase any emerging differences between populations. One way to complete speciation is through a process called reinforcement. Reinforcement occurs where natural selection favors the avoidance of hybridization when hybrid offsprings are less fit. This project uses experimental evolution—studying evolutionary change as it occurs—to track reproductive barriers between populations over time. The work will examine whether relatively weak barriers to reproduction between populations are strengthened or decay over time. Using these data, the researchers will determine the scenarios under which reinforcement can occur. As part of this project, high school, undergraduate, and graduate-level students will receive science education and training. An outreach program operating at a local middle school and scout troop will increase exposure to genetics and promote interest in science amongst underrepresented groups. Evidence for and against the evolution of reproductive isolation by reinforcement comes largely from comparative approaches and snapshot studies in natural populations. However, these methods often encounter difficulties when trying to ascribe patterns of reproductive isolation to specific evolutionary forces. This project will directly test the hypothesis that reinforcing selection can overwhelm the homogenizing force of gene flow. To test this hypothesis, the work will follow the evolution of reproductive isolation in populations of Drosophila melanogaster that show some degree of initial reproductive isolation. Some experimental populations will remain allopatric, while others will experience gene flow. In these populations, the strength of selection against hybridization will be manipulated. A time series of measures of both competitive and non-competitive reproductive isolation from these populations will reveal the answers to three questions. First, how often and how consistently is reinforcement able to strengthen reproductive isolation? Second, how strong must selection against hybrids be for this to occur? Third, is pre-mating (sexual) or postmating-prezygotic (gametic) isolation more evolutionarily labile?This project is jointly funded by Evolutionary Processes and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.