Examining variations in functional homogeneity in herbivorous coral reef fishes in Pacific Islands experiencing a range of human impacts

Abstract

Habitat loss from human impacts can lead to functional homogenization, whereby natural communities become less diverse. Herbivorous coral reef fishes display varying specialization and unique functional roles among closely related taxa, making homogenization relevant to ecosystem function. To explore whether the functional homogeneity of herbivore assemblages correlate with human impacts, we combined an index of diet specialization and a functional trait matrix with fish abundance data for > 3000 sites across the Pacific that encompass intact to degraded coral reefs. We determined the relative abundance of specialized species and the functional dissimilarity in an assemblage. Assemblage composition varied between islands, regions, and human population densities, with generalist species such as Acanthurus nigrofuscus dominating in highly populated locations. Spatial patterns and variability in the relationship between herbivorous reef fish assemblages and human impacts showed local and indirect effects. Despite broad variability, herbivore diversity decreased with human impacts among populated islands, consistent with the hypothesis that human impacts can lead to functional homogenization of coral reef fish communities.

Keywords

• Functional homogeneity
• Specialization
• Herbivory
• Anthropogenic impacts