The relationship between sexual size dimorphism and habitat use in GreaterAntillean Anolis Lizards

Sexual size dimorphism (SSD) is the evolutionary result of selection operat ing differently on the body sizes of males and females. Anolis lizard speci es of the Greater Antilles have been classified into ecomorph classes, larg ely on the basis of their structural habitat (perch height and diameter). W e show that the major ecomorph classes differ in degree of SSD. At least tw o SSD classes are supported: high SSD (trunk-crown, trunk-ground) and low S SD (trunk, crown-giant, grass-bush, twig). Differences cannot be attributed to an allometric increase of SSD with body size or to a phylogenetic effec t. A third explanation, that selective pressures on male and/or female body size vary among habitat types, is examined by evaluating expectations from the major relevant kinds of selective pressures. Although no one kind of s elective pressure produces expectations consistent with all of the informat ion, competition with respect to structural habitat and sexual selection pr essures are more likely possibilities than competition with respect to prey size or optimal feeding pressures. The existence of habitat-specific sexua l dimorphism suggests that adaptation of Anolis species to their environmen t is more complex than previously appreciated.