Odd species out as predators reduce diversity of coral-reef fishes

When predators differentiate among prey species, they commonly select the most abundant species. Surprisingly, on coral reefs in Australia and the Bahamas, we found evidence to the contrary: using null models, we observed that generalist predators had a greater impact on less-abundant species, thereby reducing local species richness. Disproportionate effects on these rare species were evident during a narrow window of time between settlement and 1-2 days later, highlighting how interactions during or immediately following settlement may influence subsequent community structure. Differences in species richness between treatments that were established during this narrow window of time eventually disappeared from reefs in Australia but persisted on reefs in the Bahamas. Our results highlight an unexpected and largely unexplored ecological interaction whereby predators reduce prey diversity.