Corals are experiencing unprecedented decline from climate change-induced mass bleaching. Although mechanisms such as demographic and genetic rescue are hypothesized to contribute to corals’ adaptive response, the persistence of spatially-realistic coral meta-communities has yet to be assessed within an eco-evolutionary framework. Here, we quantify the effects of dispersal network structure on the adaptive response of corals in three systems: the Coral Triangle, the Southwest Pacific, and the Caribbean. We track the percent cover of two coral functional types: a coral with fast growth and narrow temperature tolerance, and a coral with slow growth and wide temperature tolerance. Both coral types compete against macroalgae and disperse through network-space based on connectivity matrices obtained from published biophysical simulations. To test the effects of environmental change on each system, we perform temperature increase experiments using RCP 4.5 and 8.5 and track coral cover in each region. We introduce a novel metric, larval trait mismatch, which quantifies the difference between the optimal trait value at a patch and its mean incoming larval trait. We relate this metric and others (e.g. modularity, self-recruitment, source/destination strength) to patch- and network-level dynamics to characterize the influence of the dispersal network on metacommunity persistence.
Results/Conclusions
Overall, the Coral Triangle exhibited the highest survivorship under RCP 4.5 and 8.5, and maintained the highest total coral cover under both scenarios. Under RCP 4.5, the Caribbean retained the least coral cover at year 2100, and declined to mean aggregate coral cover levels of below 1% (i.e. effective extinction threshold) at the fastest rate among the three regions. The Coral Triangle remained above the extinction threshold for the entirety of the simulation. Under RCP 8.5, the Southwest Pacific region retained the least coral cover at year 2100, and both the Southwest Pacific and the Caribbean fell below the extinction threshold at the network scale at year 2067, while the Coral Triangle remained above 1% cover for another 10 years. Overall, our simulations produce differences in effective extinction time of 10 to over 100 years among regions, and the dominant coral type was dependent on region. Our work suggests that regional differences in connectivity and sea surface temperature partially account for the observed differences in adaptive capacity of the three regions to ocean warming.