Genetic Variation in Heat Tolerance of the Coral Platygyra Daedalea Indicates Potential for Adaptation to Ocean Warming

Platygyra daedalea from the Great Barrier Reef was assessed for heritability and genetic variation associated with heat tolerance.Survival of ten quantitative genetic crosses of larvae produced form six parental colonies in a heat tolerance selection experiment.Six colony fragments of Platygyra daedalea were collected from Esk Reef, an inshore reef in the central region of the Great Barrier Reef. Colonies were held in aquaria and spawned in November 2016. Eggs and sperm bundles were collected and combined to produce 10 family crosses. Larval survival during controlled heat stress exposure experiments were then conducted:1. Six replicates of 20 larvae from each cross were randomly allocated to each of two temperature treatments: ambient temperature 27°C or acute heat stress 35.5°C. Mortality data were recorded every 12 hours for 10 days.Survival under heat stress was modelled using a Kaplan Meier Survival Analysis and a Cox Proportional Hazards (CPH Survival under heat stress was modelled using a Kaplan Meier Survival Analysis and a Cox Proportional Hazards (CPH) model) model using the Survival package in R (Therneau and Grambsch, 2000)2. A selection experiment to identify changes in allele frequency in response to acute heat exposure. Four replicates of 500 larvae per cross were allocated into 1L flow-through culture containers for a total of 2000 larvae in each of two temperature treatments (27°C and 35.5°C). At 53 hours, 100 larvae from each replicate were sampled (total 400), and preserved for genetic analysis.Following genomic library preparation and sequence processing, the allele frequency analysis was evaluated as well as comparison of genotyped SNPs between crosses.Full details of the survival in heat stress experiments and quantitative genetic analysis of variation in heat tolerance can be found in Elder et al., (2022).