Department of Environmental Toxicology and Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616, USA.
Department of Biological Sciences, California Polytechnic State University, San Luis Obispo, CA 93407, USA.
Integr Comp Biol. 2021 Nov 17;61(5):1730-1740. doi: 10.1093/icb/icab185.
The presence of standing genetic variation will play a role in determining a population's capacity to adapt to environmentally relevant stressors. In the Gulf of Mexico, extreme climatic events and anthropogenic changes to local hydrology will expose productive oyster breeding grounds to stressful low salinity conditions. We identified genetic variation for performance under low salinity (due to the combined effects of low salinity and genetic load) using a single-generation selection experiment on larvae from two populations of the eastern oyster, Crassostrea virginica. We used pool-sequencing to test for allele frequency differences at 152 salinity-associated genes for larval families pre- and post-low salinity exposure. Our results have implications for how evolutionary change occurs during early life history stages at environmentally relevant salinities. Consistent with observations of high genetic load observed in oysters, we demonstrate evidence for purging of deleterious alleles at the larval stage in C. virginica. In addition, we observe increases in allele frequencies at multiple loci, suggesting that natural selection for low salinity performance at the larval stage can act as a filter for genotypes found in adult populations.
存在稳定的遗传变异将在决定种群适应环境相关胁迫方面发挥作用。在墨西哥湾，极端气候事件和对当地水文学的人为改变将使产牡蛎繁殖地面临具有胁迫性的低盐度条件。我们使用来自两个东方牡蛎（Crassostrea virginica）种群的幼虫进行了一代选择实验，确定了在低盐度下的表现遗传变异（由于低盐度和遗传负荷的综合影响）。我们使用池测序技术，在低盐度暴露前后，对与盐度相关的 152 个基因的幼虫家族进行了等位基因频率差异测试。我们的研究结果对于在环境相关盐度下的早期生活史阶段，进化变化是如何发生的具有重要意义。与牡蛎中观察到的高遗传负荷一致，我们在 C. virginica 幼虫阶段证明了清除有害等位基因的证据。此外，我们观察到多个基因座的等位基因频率增加，这表明在幼虫阶段对低盐度性能的自然选择可以作为成年种群中基因型的筛选。
