SEXUAL SIZE DIMORPHISM AND ECOLOGY - THE CASE OF A TROPICAL LIZARD, TROPIDURUS-MELANOPLEURUS (SAURIA, TROPIDURIDAE)

Tropidurus melanopleurus is a highly dimorphic tropidurid lizard that is found on the eastern slopes of the Andes from Argentina to Peru. Ad ult males are larger than females and also have longer and wider heads . The hind legs show isometric growth in females and negative allometr ic growth in males, as do head width and head length of both sexes. Se xes differ in thermoregulation and diet. Males appear to be thermoregu lators, whereas females are thermoconformers. Females are active over broader ranges of body temperature. Males prey upon a wide variety of arthropods, whereas females have a narrow myrmecophagous diet. At pres ent, it is not possible to decide whether sexual or natural selection explains the sexual dimorphism observed in T. melanopleurus. Body size could be the product of sexual selection modified by ecological facto rs.