Grapsus grapsus and Grapsus adscensionis are supralittoral crabs that are known to inhabit oceanic islands and depend on surface currents to recruit in the rocky shores. The ornamentation of the cephalothorax is very distinct among species, but morphological differences are controversial, and integrative studies with different approaches are needed. This study investigated the genetic variation among the populations of G. grapsus from Saint Peter and Saint Paul Archipelago (SP), Fernando de Noronha (FN), Rocas Atoll (RA) and Trindade Island (TR) in the western Atlantic, and G. adscensionis from the islands of Ascension (AI) and Saint Helena (SH) in the mid-Atlantic. Morphology was assessed by geometric morphometric analyses of the carapace and chelae, and numerical analyses of tubercles in the frontal plate of SP, FN, RA, TR and AI populations. In addition, dispersal of the larvae in the Atlantic Ocean was simulated performing a Lagrangian analysis using HYCOM reanalysis dataset as the ocean surface velocity field. The data obtained for the mitochondrial D-loop gene confirmed the distinctness of the two putative species and demonstrated the connectivity between the populations of G. grapsus from the three equatorial islands. The TR population presented unique haplotypes, as well as AI and SH. The geometric morphometric analyses showed differentiation between the carapace shapes for G. grapsus and G. adscensionis, however, the chelae shape does not allow to distinguish between the species or the population. The morphometric and molecular results were consistent with the pattern of particles dispersion in the Atlantic ocean. The larvae of SP, FN and RA mix after two months of drift, while the larvae of TR, AI, SH circulate only around the respective islands. The results reinforce the validation of the two species and the isolation of populations of G. grapsus in TR and of G. adscensionis in AI and SH. The populations of these islands might be maintained by self-recruitment, through larval behavior associated with the local current system, and therefore should be the target of conservation measures.

Grapsus grapsus和Grapsus adscensionis是已知栖息于海洋岛屿并依靠地表水流在岩石海岸招募的上岸螃蟹。头胸部的纹饰在不同物种间差异很大，但形态差异存在争议，需要采用不同方法进行综合研究。这项研究调查了来自圣彼得和圣保罗群岛 (SP)、费尔南多·迪诺罗尼亚群岛 (FN)、罗卡斯环礁 (RA) 和特林达德岛 (TR) 西大西洋的G. grapsus种群之间的遗传变异。广告来自大西洋中部的阿森松岛 (AI) 和圣赫勒拿岛 (SH)。通过背甲和螯的几何形态测量分析以及 SP、FN、RA、TR 和 AI 种群额板结节的数值分析来评估形态。此外，使用 HYCOM 再分析数据集作为海洋表面速度场，通过拉格朗日分析模拟了大西洋中幼虫的扩散。获得的线粒体 D-loop 基因数据证实了两个假定物种的独特性，并证明了来自三个赤道岛屿的G.grapsus种群之间的连通性。TR 群体呈现出独特的单倍型，以及 AI 和 SH。几何形态测量分析表明甲壳形状之间存在差异然而，G. grapsus和G. adscensionis，螯的形状不允许区分物种或种群。形态测量和分子结果与大西洋中颗粒分散的模式一致。SP、FN和RA的幼虫在漂流两个月后混合，而TR、AI、SH的幼虫只在各自的岛屿周围循环。结果加强了对这两个物种的验证以及TR中G. grapsus种群和AI 和 SH中G. adscensionis种群的分离。这些岛屿的种群可能通过与当地当前系统相关的幼虫行为自我招募来维持，因此应该成为保护措施的目标。