Abstract

Significance Our results indicate that, even in highly diverse systems like coral reefs, we can no longer assume that the erosion of species diversity can be discounted by the high probability of functional redundancy: i.e., that several species can support the same function. Indeed, we show that fish species tend to disproportionately pack into a few particular functions while leaving many functions highly vulnerable, i.e., they are supported by just one species. Even the Coral Triangle, which has a high concentration of tropical-reef fishes, may experience a loss of functional diversity following fisheries pressure and local species extirpation. Our results suggest that the promised benefits of functional insurance from high species diversity may not be as strong as we once hoped.