Circumtropical patterns in butterflyfish communities

Synopsis Butterflyfish species richness increases along a longitudinal circumtropical gradient from lows of 3–5 species in the tropical Atlantic and Eastern Pacific to highs of 40 or more in the Indo-Pacific region. Biomass of the fishes increases as species richness increases, and single-site (alpha) diversity increases as does between-site (beta) diversity. There is no evidence of density compensation in richer communities, but at the level of islands and regions, habitat breadth diminishes as species richness increases. Morphologically, species are added to communities both at the boundaries and in the middle of morphospace.