Population connectivity and genetic offset in the spawning coral Acropora digitifera in Western Australia

Anthropogenic climate change has caused widespread loss of species
biodiversity and ecosystem productivity across the globe, particularly on
tropical coral reefs. Predicting the future vulnerability of reef-building
corals, the foundation species of coral reef ecosystems, is crucial for
cost-effective conservation planning in the Anthropocene. In this study,
we combine regional population genetic connectivity and seascape analyses
to explore patterns of genetic offset (the mismatch of gene-environmental
associations under future climate conditions) in Acropora digitifera
across 12 degrees of latitude in Western Australia. Our data revealed a
pattern of restricted gene flow and limited genetic connectivity among
geographically distant reef systems. Environmental association analyses
identified a suite of loci strongly associated with the regional
temperature variation. These loci helped forecasting future genetic offset
in random forest and generalised dissimilarity models. These analyses
predicted pronounced differences in the response of different reef systems
in Western Australia to rising temperatures. Under the most optimistic
future warming predictions (RCP 2.6), we observed a general pattern of
increasing genetic offset with latitude. Under the most extreme climate
scenario (RCP 8.5 in 2090-2100), coral populations at the Ningaloo World
Heritage Area were predicted to experience a higher mismatch in genetic
composition, compared to populations in the inshore Kimberley region. The
study suggest complex and spatially heterogeneous patterns of
climate-change vulnerability in coral populations across Western
Australia, reinforcing the notion that regionally tailored conservation
efforts will be most effective at managing coral reef resilience into the
future.