Reef size and isolation determine the temporal stability of coral reef fish populations

Temporal variance in species abundance, a potential driver of extinction, is
linked to mean abundance through Taylor’s power law, the empirical observation of a linear
log–log relationship with a slope between 1 and 2 for most species. Here we test the idea that
the slope of Taylor’s power law can vary both among species and spatially as a function of
habitat area and isolation. We used the world’s most extensive database of coral reef fish
communities comprising a 15-year series of fish abundances on 43 reefs of Australia’s Great
Barrier Reef. Greater temporal variances were observed at small and isolated reefs, and lower
variances at large and connected ones. The combination of reef area and isolation was
associated with an even greater effect on temporal variances, indicating strong empirical
support for the idea that populations on small and isolated reefs will succumb more frequently
to local extinction via higher temporal variability, resulting in lower resilience at the
community level. Based on these relationships, we constructed a regional predictive map of the
dynamic fragility of coral reef fish assemblages on the Great Barrier Reef.

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