Meeting Abstract
Can corals adapt to the current rate of sea surface warming? One possibility for such rapid adaptation is by “genetic rescue”, involving the spread of pre-existing heat-tolerance alleles from warmer to cooler locations. We have developed an individual-based model of this process and used it to generate a map of times to extinction for the whole Coral Triangle. We used a migration matrix between >600 reefs derived from the biophysical model of larval dispersal and assumed relative population sizes proportional to the reef area. Varying the poorly known parameters of the adaptation model, such as heritability and plasticity of heat tolerance, number and effect size of adaptive loci, and absolute population size, had little effect on the ranking of reefs according to time to extinction (Spearman rho >0.89 between alternative parameter settings). Present-day temperature is the strongest predictor of time to extinction, explaining 51% of variation (warmer locations go extinct sooner), followed by reef area (21% of variation explained, smaller reefs go extinct sooner) and immigration rate (6% of variation explained, higher immigration delays extinction). Reefs that are predicted to survive the longest are well-connected high-latitude reefs such as middle and southern Great Barrier Reef and Lord Howe Island. The most rapid extinction is predicted for isolated reefs in already warm locations, such as Thailand, Cambodia, and Gulf of Carpentaria. Notably, reefs in Western Australia are also predicted to go extinct relatively soon despite their high-latitude location, due to the lack of immigration from warm-adapted populations. We show that coral extinction at these reefs can be substantially delayed through feasible assisted migration efforts.
