Animal migrations are a fascinating and global phenomenon, yet they are often difficult to study and sometimes poorly understood. Here, we build on classic ecological theory by hypothesizing that some enigmatic spawning migrations across ocean habitats can be inferred from a population genetic signature of larval dispersal by ocean currents. We test this assumption by integrating spatially-realistic simulations of alternative spawning migration routes, associated patterns of larval dispersal, and associated variation in the population genetic structure of eastern Australian sea mullet (Mugil cephalus). We then use simulation results to assess the implications of alternative spawning destinations for larval replenishment, and we contrast simulated against measured population genetic variation. Both analyses suggest that the spawning migrations of M. cephalus in eastern Australia are likely to be localized (approximately 100 km along the shore), and that spawning is likely to occur in inshore waters. Our conclusions are supported by multiple lines of evidence available through independent studies, but they challenge the more traditional assumption of a single, long-distance migration event with subsequent offshore spawning in the East Australian Current. More generally, our study operationalizes classic theory on the relationship between fish migrations, ocean currents and reproductive success. However, rather than confirming the traditionally assumed adaptation of migratory behaviour to dominant ocean current flow, our findings support the concept of a genetically measurable link between fish migrations and local oceanographic conditions, specifically water temperature and coastal retention of larvae. We believe that future studies using similar approaches for high resolution and spatially-realistic ecological-genetic scenario testing can help rapidly advance our understanding of key ecological processes in many other marine species.

中文翻译：

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洋流和鱼类迁徙的种群遗传特征

动物迁徙是一种引人入胜的全球现象，但它们往往难以研究，有时也知之甚少。在这里，我们以经典生态理论为基础，假设可以从洋流传播幼虫的种群遗传特征推断出一些跨越海洋栖息地的神秘产卵迁移。我们通过整合替代产卵迁徙路线的空间真实模拟、幼虫扩散的相关模式以及澳大利亚东部海鱼（Mugil cephalus）种群遗传结构的相关变异来测试这一假设。然后，我们使用模拟结果来评估替代产卵目的地对幼虫补充的影响，并将模拟与测量的种群遗传变异进行对比。两种分析都表明 M. 澳大利亚东部的 cephalus 可能是局部的（沿海岸约 100 公里），并且产卵可能发生在近海水域。我们的结论得到了通过独立研究获得的多条证据的支持，但它们挑战了更传统的假设，即单一的长距离迁移事件，随后在东澳大利亚洋流中产生离岸产卵。更一般地说，我们的研究将关于鱼类洄游、洋流和繁殖成功之间关系的经典理论付诸实践。然而，我们的研究结果并没有证实传统上假设的迁徙行为对主导洋流的适应性，而是支持鱼类迁徙与当地海洋条件之间的遗传可测量联系的概念，特别是水温和幼虫的沿海滞留。我们相信，未来使用类似方法进行高分辨率和空间逼真的生态遗传情景测试的研究可以帮助我们快速了解许多其他海洋物种的关键生态过程。