Department of Biology, Institute of Environment, Florida International University (FIU), Miami, FL 33199, USA.
Laboratory of Bioecology and Systematics of Crustaceans (LBSC), Faculty of Philosophy, Sciences and Letters at Ribeirão Preto (FFCLRP), University of São Paulo (USP), Ribeirão Preto 14040-901, Brazil.
Genes (Basel). 2022 Dec 1;13(12):2263. doi: 10.3390/genes13122263.
The Amazon-Orinoco plume (AOP) is the world's largest freshwater and sediment discharge into the ocean. Previous studies limited to mtDNA suggest that the swimming crab Ordway, 1863 exists as two distinct genetic clusters separated by the AOP. However, questions concerning migration, diversification time, and species delimitation are unresolved. Densely sampling markers across the genome (SNPs) could elucidate the evolutionary processes within this species. Here, we combined mtDNA data and ddRAD-seq to explore the diversification patterns and processes within the swimming crab . We show great genetic differentiation between groups on the north and south sides of the plume but also signs of hybridization. Demographic modeling indicates the divergence between groups starting around 8 Mya following the AOP's formation. After a period of isolation, we detect two incidences of secondary contact with stronger migration in concordance with the North Brazil Current flow. Our results suggest speciation with gene flow explained by the interplay among the AOP, oceanographic currents, and long larval dispersal. This work represents the first investigation employing ddRAD-seq in a marine invertebrate species with distribution encompassing the north and south Atlantic and sheds light on the role of the AOP in the diversification of a marine species.
亚马孙-奥里诺科羽流（AOP）是世界上最大的淡水和沉积物入海通量。先前基于 mtDNA 的研究表明，游泳蟹 Ordway, 1863 存在两个由 AOP 分隔的独特遗传集群。然而，关于洄游、多样化时间和物种划分的问题仍未解决。在全基因组范围内密集采样标记（SNP）可以阐明该物种内的进化过程。在这里，我们结合 mtDNA 数据和 ddRAD-seq 来探索游泳蟹的多样化模式和过程。我们显示了羽流南北两侧群体之间存在巨大的遗传分化，但也存在杂交的迹象。种群动态模型表明，在 AOP 形成后，群体之间的分歧始于约 800 万年前。在一段隔离期后，我们检测到两次与北巴西洋流一致的次级接触，伴随着更强的迁移。我们的结果表明，基因流动解释了 AOP、海洋流和长期幼虫扩散之间的相互作用，导致了有洄游习性的物种形成。这项工作代表了首次在分布范围涵盖北大西洋和南大西洋的海洋无脊椎动物物种中使用 ddRAD-seq 进行的研究，揭示了 AOP 在海洋物种多样化中的作用。
