Alternative reproductive tactics, where members of a population exhibit divergent mating approaches, are widespread in fishes. The maintenance of such polymorphisms is often explained using game-theoretic concepts such as frequency-dependent selection, which typically assume populations are at equilibrium. However, fish populations exhibit stochastic variability that is inconsistent with the assumption of equilibrium dynamics. We explored how stochastic population dynamics interact with sexual and harvest-induced selection to shape the frequencies of alternative male phenotypes in Pacific salmon (Oncorhynchus spp., Salmonidae). Males of several salmon species are composed of typical “hooknoses” that compete on the spawning grounds for mating opportunities, and rarer “jacks” that mature younger and at smaller sizes to attempt reproduction by “sneaking.” Using stochastic simulations, we found that realistic levels of recruitment variation could increase the prevalence of jacks relative to equilibrium expectations. This result is attributable to the “cohort mismatch” phenomenon, whereby differences in age at maturity between male phenotypes cause jacks from strong recruitments to spawn in the same year as hooknoses from weaker cohorts, elevating the proportion of jacks among spawners. Simulations were supported by data from major populations of sockeye salmon (O. nerka, Salmonidae) throughout their North American range, which indicated a positive association between recruitment variability and jack prevalence in some regions. Moreover, we found that frequency-dependent mating dampened population responses to fisheries-induced selection. Our findings emphasize that stochastic ecological processes are important to the maintenance of alternative life histories and interact with selection to produce emergent dynamics that have not previously been recognized.

中文翻译：

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随机招募改变了年龄结构人群中另类生活史的频率

替代繁殖策略，其中种群成员表现出不同的交配方法，在鱼类中很普遍。这种多态性的维持通常使用博弈论概念来解释，例如频率相关选择，通常假设种群处于平衡状态。然而，鱼类种群表现出与平衡动态假设不一致的随机变异性。我们探讨了随机种群动态如何与性选择和收获诱导选择相互作用，以塑造太平洋鲑鱼（Oncorhynchus属，鲑科）。几种鲑鱼的雄性由典型的“钩鼻”组成，它们在产卵场竞争交配机会，而稀有的“杰克”则成熟得更年轻、体型更小，以通过“潜行”尝试繁殖。使用随机模拟，我们发现招聘变化的现实水平可能会增加相对于均衡预期的 jacks 的流行。这一结果归因于“队列不匹配”现象，即雄性表型之间成熟年龄的差异导致来自强招募的杰克与来自较弱队列的钩鼻在同一年产卵，从而提高了产卵者中杰克的比例。模拟得到了红鲑鱼主要种群数据的支持（O. nerka,Salmonidae）在其整个北美范围内，这表明某些地区的招募变异性与 jack 流行之间存在正相关。此外，我们发现频率依赖性交配抑制了种群对渔业诱导选择的反应。我们的研究结果强调，随机生态过程对于维持替代生活史很重要，并与选择相互作用以产生以前未被认识到的紧急动态。