Hydrothermal vent fauna of the western Pacific Ocean: Distribution patterns and biogeographic networks

Aim: Deep-sea hydrothermal vent habitats support a low-diversity fauna in which most species are unique to the ecosystem. To inform conservation planning around this vulnerable marine ecosystem, we examine species distributions over a wide area to assess the underlying beta-diversity components and to examine biogeographic patterns. We assess the concept of a highly connected fauna that would repopulate areas of local extinction from distal locations. Location: Western Pacific Ocean from Japan to New Zealand. Methods: We assemble a database of 295 confirmed species records for 11 western Pacific vent systems. The SET beta-diversity framework supports query of the distribution of pairwise pattern components in comparisons among vent systems. We build a network based in graph theory to examine connectivity among vent systems based on shared species similarity. A bipartite network revealed the relative role of each species in linkages among vent system nodes. We assess the importance of sampling bias and distance between systems. Results: Overall, two-thirds of the taxa are restricted to a single basin or arc. The Mariana Trough system has the highest corrected weighted endemism for vent-specific species, followed by that of the Okinawa Trough. Species replacement is the dominant feature of beta-diversity. Eleven vent systems form seven network modules with stronger connectivity in the Southwest than Northwest Pacific. The Manus Basin vent system emerges as a network ‘hub’ reflecting its central geographic near the equator. Main Conclusion: Two western Pacific biogeographic provinces arise, north and south of the equator that few species transcend. Local and regional conservation plans should consider the low network connectivity and high system endemism in management of hydrothermal vent ecosystems in the event of seabed mining. Species recruitment is unlikely to transcend vent system boundaries. We identify Okinawa Trough, Mariana Trough, Manus Basin, Feni-Tabar Arc and Kermadec Arc for development of conservation plans that initiate or expand protection.

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