Proceedings of the United States National Museum SMITHSONIAN INSTITUTION • WASHINGTON, D.C. Volume 125 1968 Number 3658 Interspecific Competition in the Tropical Rain Forest: Ecological Distribution Among Lizards at Belem, Para By A. Stanley Rand and Stephen S. Humphrey The ecological differences between sympatric species have proved useful foci for ecological studies, particularly those with an evolu-tionary viewpoint. The information provided by such studies is relevant to considerations of interspecific competition and to the problem of the causes of tropical species diversity. In general, it is assumed that a species' closest competitors in an area are its nearest relatives. This is probably true within generic and specific groups, but, as this study suggests, it may not be true for higher categories. Studies on the ecology of sympatric lizards (usually restricted to sympatric congeners) have been made at several localities by various workers, among them Milstead (1957), Inger (1959), Collette (1961), Rand (1964). Little has been published about the ecology of the lizards of lowland tropical forests and almost nothing about those in the rain forests of the Amazon. The study most comparable to the present one is that of Sexton, Heatwole, and Knight (1964) in Panama. ^Rand: Smithsonian Tropical Research Institute, Balboa, Canal Zone; Humphrey: 612 Louisiana St., Lawrence, Kansas. 1
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