A Search for Pattern in Butterfly Fish Communities

Abstract

The species richness and individual abundance of butterfly fishes increase with coral density. There is no evidence of either density compensation or place-niche compression as the number of species increases from 2 to 17, although place-niche overlap does increase slightly along this gradient. Real place niches and overlaps are uniformly less than ones calculated for randomly generated communities of noninteracting species. Pairwise comparisons of species based on abundance at 14 stations revealed more positive correlations than expected, suggesting that all fishes are more common at favorable stations. Species are not randomly distributed among transects within stations, and the lower-than-expected place-niche overlap between them suggests differential habitat selection on this scale. A comparison of matrices of morphological resemblance, coexistence, and diet revealed no correlations of the sort expected if similar species were replacing each other from site to site. Our results provide little evidence that butterfly fishes are living in resource-limited communities, and suggest that their assemblages are not competitively structured. However, the communities are not random assemblages of the species of which they are composed.