Contrasting population structures of reef-building corals and their algal symbionts inform adaptive potential across the western Pacific

Contrasting population structures of reef-building corals and their algal symbionts inform adaptive potential across the western Pacific Denis H. auteur aut IRD Prata K. E. auteur aut IRD Ishida H. auteur aut IRD Popovic I. auteur aut IRD Mocellin V. J. L. auteur aut IRD Boussion Magali auteur aut IRD Byrne I. auteur aut IRD Purcell S. W. auteur aut IRD Bay L. K. auteur aut IRD Lecellier G. auteur aut IRD Chan C. X. auteur aut IRD Riginos C. auteur aut IRD Howells E. J. auteur aut IRD Berteaux-Lecellier V. auteur aut IRD text journalArticle eng text/pdf reformatted digital access The genetic diversity and connectivity of reef-building coral populations are key to their survival in warming oceans. Yet our understanding of corals' demographic resilience and adaptive potential is complicated by cryptic species diversity, wide geographic distributions, and complex coral-algal symbioses. To address these challenges, we investigated the genetic connectivity and diversity of the broadcast-spawning coral Acropora cf. spathulata and its associated Symbiodiniaceae across 29 reefs spanning the Great Barrier Reef, the Coral Sea, and New Caledonia, using whole-genome sequencing of 1,088 colonies. We identified four genetically distinct coral populations that diverged between 0.27 and 0.65 mya, likely due to geographic isolation across thousands of kilometers. These populations maintained asymmetrical gene flow along major ocean currents despite demographic isolation and sustained large local effective population sizes (similar to 2,900), supported by a high dispersal range of similar to 100 km per generation. In contrast, their Symbiodiniaceae partners varied over finer spatial scales, with five distinct Cladocopium taxa distributed along latitudinal and cross-shore gradients, likely driven by local environmental conditions. These results suggest that high dispersal capacity and large local population size promote demographic resilience within reef systems, while environment-specific symbioses and long-distance gene flow across reef systems support adaptation and evolutionary rescue. specialized PACIFIQUE PACIFIQUE OUEST 036 082 Current Biology 36 11 2808-2822.e1-e8 2026 0960-9822 https://www.documentation.ird.fr/hor/fdi:010097433 10.1016/j.cub.2026.04.057 0960-9822 [F B010097433] https://www.documentation.ird.fr/hor/fdi:010097433 https://horizon.documentation.ird.fr/exl-doc/pleins_textes/2026-07/010097433.pdf IRD - Base Horizon / Pleins textes 2026-07-09 2026-07-09 fdi:010097433 fre