Genetic structure of Turbinaria peltata in the northern South China Sea suggest insufficient genetic adaptability of relatively high-latitude scleractinian corals to environment stress.

With the rapid degradation of coral reefs due to global warming and anthropogenic impacts, relatively high-latitude areas, such as the northern South China Sea (SCS), are likely to become refuges for tropical coral species. Here we investigated the genetic features and adaptability of one dominant scleractinian coral species, Turbinaria peltata, in the northern SCS. A total of 81 samples from 5 sites were studied to explore potential mechanisms of adaptability to environmental stress as a result of climate change. Ten microsatellite markers developed in this study, one nuclear gene (internal transcribed spacer, ITS), and one mitochondrial gene (mitochondrial cytochrome oxidase subunit I gene, mtDNA COI) were used. Our results indicated that the genetic diversity of T. peltata in the northern SCS is low (A = 1.403-2.011, H = 0.105-0.248, H = 0.187-0.421) with the lowest in Dongfang population (DF) (A = 1.403, H = 0.22, H = 0.187). These results indicate that T. peltata has insufficient genetic adaptability and may unable to handle increasingly complex global changes. A significantly moderate genetic differentiation was observed among T. peltata populations (Φ = 0.167), in addition to a high genetic differentiation between DF and other populations (F = 0.272-0.536 > 0.25). The DF population near a fishing port was exposed to severe anthropogenic environmental stress, which may drive the extraordinarily high genetic differentiation between DF and other populations. Furthermore, the Mantel test results showed that the genetic differentiation of the other four populations was strongly correlated with the average sea surface temperature (SST) (R = 0.82, Mantel test P < 0.05) and geographical distance (R = 0.57, Mantel test P < 0.05). Our results suggest that the genetic structure of T. peltata in the relatively high-latitude of the SCS was significantly affected by average SST, geographical isolation, and anthropogenic activities. These findings provide a theoretical foundation for the protection of relatively high-latitude coral reefs.