Endemic communities inhabit the vicinity of hydrothermal vents, where hot fluids laden with minerals exit the seafloor. Based on earlier morphological studies, Southwestern Pacific vents seem to present high connectivity, although dispersal barriers and directionality could impair gene flow. Mining exploitation might also participate in the gene flow reduction in the coming years, highlighting the need for before impact studies. This study objectives were to estimate the genetic diversity within five vent fields spanning nearly 5000 km and establish their connectivity, with a focus on the shrimp Alvinocarididae and scale worm Polynoidae families. Sequences obtained from the cytochrome c oxidase I (COI) gene allowed us to describe genetic diversity and gene flow between the Manus, Woodlark, North Fiji, and Lau Basins and the Futuna volcanic arc. The distribution of the 101 species identified emphasizes that hydrological, physical, and biological factors must be considered together to estimate dispersal potential. High connectivity was observed between the Manus and Woodlark Basins, on one hand and the North Fiji and Lau Basins on the other hand. The Manus Basin presented high levels of diversity and endemism. Nautilocaris saintlaurentae and Branchipolynoe tjiasmantoi had panmictic populations within the studied area. In contrast, Rimicaris variabilis presented genetic differentiation with at least four cryptic species. All species have undergone bottlenecks triggered by glaciation events, followed by population expansion.
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