GEOGRAPHICAL ECOLOGY OF A NEOTROPICAL LIZARD - AMEIVA AMEIVA (TEIIDAE) IN BRAZIL

The large-bodied teiid lizard Ameiva ameiva was studied at eight diffe rent sites in four major South American habitats of Brazil: caatinga, cerrado, Amazonian rain forest, and Amazonian savanna. We found striki ng similarity in ecological attributes of this lizard among very diffe rent habitats. Activity is concentrated in late morning and early afte rnoon; active body temperatures average 37.9 +/- 0.09 degrees C and va ry little among sites or throughout the day; the diet consists of a va riety of vertebrates and invertebrates but is dominated by grasshopper s, roaches, beetles, spiders, and insect larvae; and niche breadths fo r prey are similar among study sites but the actual composition of the diets varies. There is minimal morphological variation among sites (m ostly size); the most striking morphological variation is between the sexes. Males reach larger body sizes and have relatively larger heads than females. Juveniles have relatively larger heads than would be pre dicted on the basis of body size alone. Sexual selection may explain t he sexual differences in head size of adults, whereas the relatively l arge heads of juveniles may be associated with food competition with s ympatric teiid lizards. Clutch size varies from 1 to 11 eggs, is relat ed to female body size (snout-vent length), and varied among study sit es. Similar variation among sites occurs in egg size but not in relati ve clutch mass. An interesting positive relationship was found between body size and relative clutch mass. In a population from the state of Rondonia egg dry mass was correlated with female size, indicating tha t individual offspring size is, to some extent, a consequence of femal e size. The reproductive season is extended for all populations and it appears that predictability of rainfall may regulate the season lengt h. Reasons for the apparent success of A. ameiva in a diversity of hab itats on a large geographic scale include its large body size, foragin g mode, and preferred microhabitat (ecotones and disturbed areas).