Department of Zoology and Biodiversity Research Centre, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.
Zeeman Institute of Systems Biology and Infectious Disease Research (SBIDER), University of Warwick, Coventry, CV4 7AL, United Kingdom.
Evolution. 2021 Mar;75(3):582-599. doi: 10.1111/evo.14165. Epub 2021 Jan 26.
Antagonistic coevolution has long been suggested to help maintain host genetic variation. Although ecological and epidemiological feedbacks are known to have important consequences on coevolutionary allele-frequency dynamics, their effects on the maintenance of genetic variation remains poorly understood. Here, we extend previous work on the maintenance of genetic variation in a classic matching alleles coevolutionary model by exploring the effects of ecological and epidemiological feedbacks, where both allele frequencies and population sizes are allowed to vary over time. We find that coevolution rarely maintains more host genetic variation than expected under neutral genetic drift alone. When and if coevolution maintains or depletes genetic variation relative to neutral drift is determined, predominantly, by two factors: the deterministic stability of the Red Queen allele-frequency cycles and the chance of allele fixation in the pathogen, as this results in directional selection and depletion of genetic variation in the host. Compared to purely coevolutionary models with constant host and pathogen population sizes, ecological and epidemiological feedbacks stabilize Red Queen cycles deterministically, but population fluctuations in the pathogen increase the rate of allele fixation in the pathogen, especially in epidemiological models. Our results illustrate the importance of considering the ecological and epidemiological context in which coevolution occurs when examining the impact of Red Queen cycles on genetic variation.
长期以来，人们一直认为拮抗共进化有助于维持宿主遗传变异。尽管生态和流行病学反馈对共进化等位基因频率动态具有重要影响，但它们对遗传变异维持的影响仍知之甚少。在这里，我们通过探索生态和流行病学反馈的影响，扩展了经典匹配等位基因共进化模型中遗传变异维持的研究，其中允许等位基因频率和种群大小随时间变化。我们发现，与仅由中性遗传漂变驱动的情况相比，共进化很少能维持更多的宿主遗传变异。共进化相对于中性漂变维持或耗尽遗传变异的时间和条件，主要取决于两个因素：红皇后等位基因频率循环的确定性稳定性和病原体中等位基因固定的机会，因为这会导致宿主中遗传变异的定向选择和耗尽。与具有恒定宿主和病原体种群大小的纯粹共进化模型相比，生态和流行病学反馈确定性地稳定了红皇后循环，但病原体中的种群波动增加了病原体中等位基因固定的速度，特别是在流行病学模型中。我们的研究结果表明，在研究红皇后循环对遗传变异的影响时，考虑共进化发生的生态和流行病学背景非常重要。
