Leveraging new knowledge of Symbiodinium community regulation in corals for conservation and reef restoration

Recent advances in quantifying the heritability of Symbiodinium communities associated with corals across a range of reproductive and symbiont transmission modes raise the possibility that corals have more options for responding to a changing environment than previously thought. Here we synthesize recent findings to develop a new perspective on coral-symbiont transmission and explore the relevance of these findings to the development of novel coral reef conservation and management tools. Evidence of diversity in Symbiodinium communities among juvenile corals can be attributed to variation in the host genotype acquired. This highlights the importance of inheriting a genetic architecture for regulating Symbiodinium community composition that is flexible enough to respond to changing environmental conditions. Emerging evidence from 8 species now exists that the strength and fidelity of coral-Symbiodinium associations differ from current paradigms based on host reproductive and symbiont transmission mode. This evidence supports that rapid adaptive responses of the holobiont through variations in Symbiodinium community structure are possible. Importantly, evidence of heritable variation in Symbiodinium communities indicates that adaptation through natural selection on this community is possible and that the strength of the response will depend on estimates of both heritability and phenotypic variance. We also present a novel analysis applying these results to quantitative genetic theory to model manipulative adaptive shifts. In combination, recent heritability estimates (h(2)) reviewed here highlight that inheritance of genes for regulating Symbiodinium community structure represents a previously unquantified mechanism by which juvenile corals may adapt to increasing environmental pressures, particularly those due to climate change.