The ‘diversity–stability hypothesis’, in which higher species diversity within
biological communities buffers the risk of ecological collapse, is now generally
accepted. However, empirical evidence for a relationship between b-diversity
(spatial turnover in community structure) and temporal stability in community
structure remains equivocal, despite important implications for theoretical ecology
and conservation biology. Here, we report strong b-diversity–stability
relationships across a broad sample of fish taxa on Australia’s Great Barrier
Reef. These relationships were robust to random sampling error and spatial
and environmental factors, such as latitude, reef size and isolation. While
b-diversity was positively associated with temporal stability at the community
level, the relationship was negative for some taxa, for example surgeonfishes
(Acanthuridae), one of the most abundant reef fish families. This demonstrates
that the b-diversity–stability relationship should not be indiscriminately
assumed for all taxa, but that a species’ risk of extirpation in response to disturbance
is likely to be taxon specific and trait based. By combining predictions of
spatial and temporal turnover across the study area with observations in
marine-protected areas, we conclude that protection alone does not necessarily
confer temporal stability and that taxon-specific considerations will improve
the outcome of conservation efforts.