Conservation priorities for reef-building coral biodiversity across multiple dimensions in the South China Sea

Biodiversity underpins ecosystem stability and the provision of ecosystem services. As the foundation species for the most biodiverse ecosystem, reef-building corals are under threat globally, including in the South China Sea (SCS). Therefore, there is an urgent need to assess their multidimensional biodiversity and identify priority areas for conservation. To address this, we conducted a survey of coral communities across 36 reef sites spanning 12 degrees of latitude in the SCS in 2022 to investigate their coral species richness, assemblage composition, and coverage. Meanwhile, seven coral functional traits and phylogenetic trees were integrated to estimate functional and phylogenetic diversity. Linear regression models and null models were used to examine the relationships among diversity indicators. Our analysis revealed significant positive correlations between species richness, functional diversity, and phylogenetic diversity. However, the correlations between coral cover and the three aforementioned diversity metrics were relatively weak. Notably, the expected functional diversity within coral communities often fell short of observed values, while expected phylogenetic diversity exhibited variable patterns, suggesting that functional and phylogenetic diversity may provide more insight into specialized habitats for conservation. Based on the relationships between coral cover, community structure, and multidimensional biodiversity, we constructed a comprehensive framework for identifying conservation priority areas. The framework shows that all aspects of the community are effective in providing information for finding conservation priorities. Overall, we provide a new framework for assessing coral conservation priority areas from an integrated perspective and contribute to conservation planning for coral reefs in the SCS.