Distribution patterns of reef-building corals in the Northwest Pacific and their environmental drivers

Understanding species distribution and the related driving processes is a fundamental issue in ecology. However, incomplete data on reef-building corals in the ecoregions of the South China Sea have hindered a comprehensive understanding of coral distribution patterns and their ecological drivers in the Northwest Pacific (NWP). This study investigated the coral species diversity and distribution patterns in the NWP by collecting species presence/absence data from the South China Sea and compiling an extensive species distribution database for the region, and explored their major environmental drivers. Our NWP coral database included 612 recorded coral species across 15 ecoregions. Of these, 536 coral species were recorded in the South China Sea Oceanic Islands after compilation, confirming the extraordinary coral species diversity in this ecoregion. Coral alpha diversity was found to decrease with increasing latitude in the whole NWP, while the influence of the Kuroshio Current on environmental conditions in its path results in a slower decline in species richness with latitude compared to regions within the South China Sea. Beta-diversity decomposition revealed that nestedness patterns mainly occurred between low and high latitude ecoregions, while communities within similar latitudes exhibited a turnover component, particularly pronounced at high latitudes. The impact of environmental factors on coral assemblage structure outweighed the effects of spatial distance. Temperature, especially winter temperature, and light intensity strongly influenced alpha diversity and beta diversity's nestedness component. Additionally, turbidity and winter temperature variations at high latitudes contributed to the turnover pattern observed among communities in the NWP. These findings elucidate the assembly processes and major environmental drivers shaping different coral communities in the NWP, highlighting the significant role of specific environmental filtering in coral distribution patterns and providing valuable insights for coral species conservation efforts.