A Morphological Comparison of Island and Mainland Assemblages of Neotropical Birds

Abstract

serine birds, composed of assemblages from 8 distinct habitats replicated over 5 areas located in Panama, Trinidad, Jamaica, St. Lucia, and St. Kitts. The structure of morphological space was very similar among the 5 localities, despite widely varying numbers of species, genera and families. The level of species packing, the evenness of species packing, and the volume of morphological space occupied in a community varied with locality and habitat, but locality explained a much higher percentage of the overall variation than did habitat for all 3 parameters. The correlation of the level of species packing with the number of species was not different from an expectation based on random assembly within each locality, though the overall locality effects were different from such an expectation. The volume of space occupied by a community was correlated with the number of species, in contrast to the expectation from random assembly, at nearly every level of analysis. The correlations of the evenness of species packing with number of species were inconsistent with the expectation from random assembly only in some cases. The extraordinary evenness of species packing on the small islands and the greater morphological distance between nearest neighbor species on those islands suggest that species interactions may prove more important in these areas than elsewhere for determining the community structure of passerine bird assemblages.