The ongoing decline of large marine vertebrates must be urgently mitigated, particularly under increasing levels of climate change and other anthropogenic pressures. However, characterizing the connectivity among populations remains one of the greatest challenges for the effective conservation of an increasing number of endangered species. Achieving conservation targets requires an understanding of which seascape features influence dispersal and subsequent genetic structure. This is particularly challenging for adult-disperser species, and when distribution-wide sampling is difficult. Here, we developed a two-step modelling framework to investigate how seascape features drive the genetic connectivity of marine species without larval dispersal, to better guide the design of marine protected area networks and corridors. We applied this framework to the endangered grey reef shark, Carcharhinus amblyrhynchos, a reef-associated shark distributed across the tropical Indo-Pacific. In the first step, we developed a seascape genomic approach based on isolation-by-resistance models involving circuit theory applied to 515 shark samples, genotyped for 4991 nuclear single-nucleotide polymorphisms. We show that deep oceanic areas act as strong barriers to dispersal, while proximity to habitat facilitates dispersal. In the second step, we predicted the resulting genetic differentiation across the entire distribution range of the species, providing both local and global-scale conservation units for future management guidance. We found that grey reef shark populations are more fragmented than expected for such a mobile species, raising concerns about the resilience of isolated populations under high anthropogenic pressures. We recommend the use of this framework to identify barriers to gene flow and to help in the delineation of conservation units at different scales, together with its integration across multiple species when considering marine spatial planning.

中文翻译：

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从海景基因组学中识别基因流动和分级保护单元的障碍：应用于海洋捕食者的建模框架

必须紧急缓解大型海洋脊椎动物的持续衰退，特别是在气候变化和其他人为压力不断增加的情况下。然而，描述种群之间的连通性仍然是有效保护越来越多的濒危物种的最大挑战之一。实现保护目标需要了解哪些海景特征会影响扩散和随后的遗传结构。这对于成年分散物种尤其具有挑战性，并且当分布范围内的采样很困难时。在这里，我们开发了一个两步建模框架，以研究海景特征如何在没有幼虫扩散的情况下推动海洋物种的遗传连通性，以更好地指导海洋保护区网络和走廊的设计。鲢鱼，一种分布在热带印度太平洋的与珊瑚礁相关的鲨鱼。第一步，我们开发了一种基于电阻隔离模型的海景基因组方法，该模型涉及应用于 515 个鲨鱼样本的电路理论，对 4991 个核单核苷酸多态性进行基因分型。我们表明，深海区域是扩散的强大障碍，而靠近栖息地则有利于扩散。在第二步中，我们预测了该物种整个分布范围内由此产生的遗传分化，为未来的管理指导提供本地和全球范围的保护单位。我们发现灰礁鲨种群比这种移动物种的预期更加分散，这引发了人们对高人为压力下孤立种群的复原力的担忧。