Geographic Variation in the Species Composition of Parrotfish (Labridae: Scarini) in the South China Sea

Since parrotfish in coral reefs are involved in key ecological processes, this study compiled species presence-absence data across 51 sites in the South China Sea to identify and explore the distribution and relationship between species and large-scale factors. A total of 50 species of parrotfish were recorded during the compilation, of which Scarus ghobban Forsskål, 1775 was the most common and widespread. The Nansha Islands, having a vast area of coral reefs and great proximity away from human interference, had the highest abundance with 41 species. Nestedness analysis indicated that the parrotfish community had statistically significant nested patterns in the South China Sea, and the Nansha Islands were the topmost site for the nested matrix rank. Scleractinian coral species richness and log(reef area) both had a significant effect on the site nested matrix rank ( p < 0.05), which supports the habitat nestedness hypothesis in the South China Sea. Compared with browsers and excavators, scrapers were determined to be the most important functional group composition, while browsers had a greater contribution to the species nested matrix rank. A linear regression model showed that parrotfish species’ richness increased with increasing longitude, scleractinian coral species richness, and reef area. Longitudinal variations in the parrotfish species richness were related to its distance from the biodiversity hotspot in the Indo-Australian Archipelago. Parrotfish were mainly distributed in the temperature range of 26–29 °C, similar to the optimum temperature for coral growth. The Nansha Islands should be considered biodiversity conservation priority areas for the conservation of parrotfish in degraded coral reef habitats, particularly in the context of increasing natural variability and anthropogenic disturbances.