Functional diversity of reef fish assemblages in the Galapagos Archipelago

Abstract

The Galapagos Archipelago's unique reef biodiversity and distribution patterns are relatively well understood compared to the study of local functional diversity processes. We investigated functional diversity patterns in coastal reef fish communities using stereo Baited Remote Underwater Videos systems (stereo-BRUVs). We collected relative abundance data based on 41,594 individual fish belonging to 121 reef fish species and assessed functional diversity using seven functional traits and a combination of functional alpha-diversity and beta-diversity indices. We found differences between bioregions; however, we observed no differences in reef fish assemblages between the geographic strata (distinct habitat types) within regions. Low functional alpha-diversity within assemblages but high environmental variability at small spatial scales has resulted in a consistent moderate functional beta-diversity between assemblages and high functional diversity at an archipelago-wide scale. While there is a low diversity of functional roles, the most abundant species represent a few distinct and supportive functional roles in Galapagos reef ecosystems. Such functional roles likely have redundancy; however, many other functional roles are likely under-represented and vulnerable. The variable functional diversity between Galapagos bioregions facilitates an ecological interpretation that supplements traditional species diversity indices. Therefore, we suggest a combination of species compositions and functional diversity metrics be used in the future management of Galapagos marine communities.