Anolis Sagrei and Anolis Cristatellus in Southern Florida: A Case Study in Interspecific Competition

This study examined the possibility of interspecific competition between Anolis sagrei and A. cristatellus, two introduced species of lizards that co—occur in the vicinity of Miami, Dade County, Florida. In an area of sympatry, structural habitat use differed significantly between the two species. Comparison of habitat use by sympatric A. sagrei and allopatric sagrei in immediately adjacent control areas revealed no significant differences. Upon removal of A. cristatellus from an area of sympatry, habitat use by A. sagrei shifted in a manner consistent with an hypothesis of interspecific competition; no such shift occurred in adjacent control populations of allopatric A. sagrei. Studies of competition that are based solely upon comparisons of resource use in sympatry and allopatry often yield spurious conclusions. On the assumption that the resource use measured in this study bears on the fitness of the two species, results of this study provide strong experimental evidence that A. sagrei and A. cristatellus are presently in competition in southern Florida.