Time scale matters: genetic analysis does not support adaptation-by-time as the mechanism for adaptive seasonal declines in kokanee reproductive lifespan

Seasonal declines of fitness-related traits are often attributed to environmental effects or individual-level decisions about reproductive timing and effort, but genetic variation may also play a role. In populations of Pacific salmon (Oncorhynchus spp.), seasonal declines in reproductive life span have been attributed to adaptation-by-time, in which divergent selection for different traits occurs among reproductively isolated temporal components of a population. We evaluated this hypothesis in kokanee (freshwater obligate Oncorhynchus nerka) by testing for temporal genetic structure in neutral and circadian-linked loci. We detected no genetic differences in presumably neutral loci among kokanee with different arrival and maturation dates within a spawning season. Similarly, we detected no temporal genetic structure in OtsClock1b, Omy1009uw, or OmyFbxw11, candidate loci associated with circadian function. The genetic evidence from this study and others indicates a lack of support for ad...与适合度相关的性状的季节性衰退，通常被归因于环境影响，或是个体在繁殖时机与繁殖投入上的决策，但遗传变异或许也发挥了一定作用。在太平洋鲑（大麻哈鱼属，Oncorhynchus spp.）种群中，繁殖寿命的季节性衰退被归因于时间适应性选择（adaptation-by-time）：即种群内生殖隔离的不同时间分化类群之间，针对不同性状存在歧向选择。我们通过检测中性位点与节律关联位点的时间遗传结构，在陆封红大马哈鱼（淡水专性大麻哈鱼，Oncorhynchus nerka）中验证了这一假说。我们未发现产卵季内到达时间与成熟时间各异的陆封红大马哈鱼，在推定的中性位点上存在遗传差异。类似地，我们在与昼夜节律功能相关的候选位点OtsClock1b、Omy1009uw及OmyFbxw11中，均未检测到时间遗传结构。本研究与既往研究的遗传证据均表明，尚无足够证据支持……