Interspecific Aggression and the Limiting Similarity of Close Competitors: The Problem of Size Gaps in Some Community Arrays

Abstract

From MacArthur''s hypothesis that interspecific aggression occurs whenever one species can expect to gain from this behavior, a model is built explicating circumstances under which limiting size similarity cannot be expected to be solely caused by resource competition. The model was developed from considerations of shorebird and waterfowl communities inhabiting open defensible terrain and in which gaps occur in size similarity sequence. In shorebird communities there exists a 2 or 3 spp. gap between cranes and sandpipers. In waterfowl communities the gap is 3 spp. In both communities natural history data suggest that interspecific aggression by the largest sequence member has eliminated intermediate sized species. Similar gaps do not occur in the rail-heron community, which inhabits an indefensible habitat.