Great Barrier Reef Platygyra daedalea harbor genetic variation in thermal tolerance that may support adaptation to warming

Reef-building corals are foundational species for one of the most diverse and productive marine ecosystems and are threatened by rising ocean temperatures. The corals of the Great Barrier Reef (GBR) have experienced two consecutive bleaching events in as many years. It is predicted that corals on the GBR will experience bleaching threshold temperatures more frequently in the future. Genetic adaptation is one mechanism for a species' survival under changing conditions. By conducting a thermal stress selection experiment which tracked survival of genotypes from genetic crosses, we quantified heritable genetic variation in Platygyra daedalea from the GBR and identified alleles after thermal stress selection. Heritability estimates of thermal tolerance suggest that the GBR P. daedalea population has the capacity to adapt with a total of 1,069 single nucleotide polymorphisms (SNPs), which underpin thermal tolerance and could allow adaptation to warming oceans.