Variable intraspecific genetic diversity effects impact thermal tolerance in a reef-building coral

Inter- and intraspecific diversity drive ecological function in many ecosystems but are poorly explored on coral reefs. To address this knowledge gap, we used larvae and adults of the brooding coral Pocillopora acuta with known parentage to examine diversity effects under temperature stress. There was a strong positive impact of increased diversity on the survival of adult corals at high temperatures, but limited or negative impacts in larvae and other metrics. This improvement was due primarily to complementarity, suggesting facilitation impacts the phenotypes of individual corals via their associated community and highlighting the critical importance of preserving diversity to preserve tolerant phenotypes that elevate community performance. We hypothesized that superoxide dismutase production could explain this pattern and describe a genomic variant that correlates with improved performance in diverse treatments; however, we found no differences in antioxidant activity between variants. These data demonstrate that some ecologically important outcomes under climate change are influenced by intraspecific diversity, which may parallel the ubiquitous functional effects of interspecific diversity. This genetic diversity may be a source of cryptic resilience on coral reefs and should be a factor in management and conservation goals because of its intrinsic positive influence on the ecosystem.