Functional Variation Among Parrotfishes: are they Complementary or Redundant?

Herbivory is a critical process that underpins coral reef structure and function. Parrotfishes play significant roles in the herbivore guild by removing macroalgae, promoting coral settlement and growth, producing sediment by bioeroding carbonate substrates, and preying on corals. This chapter addresses patterns in functional variation among parrotfishes and how species of parrotfishes are either complementary or redundant to other members of the herbivore guild. Herbivore and parrotfish diversity is critical for maintaining ecosystem function because herbivores differ in sensitivity to algal chemical, morphological, and structural defenses. In addition to complex patterns in complementarity in diet selection, parrotfish species are diverse in their spatial foraging patterns, life history strategies, habitat use, and responses to predators. This functional variation and complementarity within parrotfishes and among other herbivorous species results in important positive impacts of herbivore diversity on coral reefs. Increasing parrotfish and herbivorous fish diversity often results in increased macroalgal consumption and increased success of corals. Thus, the complementary roles that parrotfishes play are important for the ecosystem function of coral reefs.