 2003 by the American Society of Ichthyologists and Herpetologists Copeia, 2003(2), pp. 285–298 Geographical Variation in the Ecology of Populations of Some Brazilian Species of Cnemidophorus (Squamata, Teiidae) DANIEL OLIVEIRA MESQUITA AND GUARINO RINALDI COLLI We investigated geographical variation in ecological parameters among popula- tions of Cnemidophorus cryptus, Cnemidophorus gramivagus, Cnemidophorus lemniscatus, Cnemidophorus ocellifer, and Cnemidophorus parecis, from three Brazilian biomes (Cer- rado, Caatinga, and Amazonian Savannas). Lizards used mainly the open ground, with a high similarity in microhabitat use among populations. Differences in micro- habitat use probably resulted from the availability of microhabitats and not from microhabitat preferences. Body temperatures were high and little influenced by en- vironmental temperatures, there being no differences among populations. There were significant differences in diet among populations, with C. ocellifer from Caatin- ga and Cerrado consuming large quantities of termites, whereas Amazonian Savanna species used primarily ants and insect larvae. The data on reproductive seasonality indicated cyclical reproduction in seasonal biomes and continuous reproduction in unpredictable climate regions. We found significant differences in mean clutch size among populations, independent of body size, with C. lemniscatus having the smallest clutch size (1.50) and C. ocellifer from Cerrado the largest (2.10). There were fewer differences in clutch size among species from Amazonian Savannas, than between populations of C. ocellifer from Caatinga and Cerrado. Apparently, populations un- der seasonal climates concentrate their reproductive effort during the short repro- ductive season, producing larger clutches, whereas those under more stable or un- predictable climates reproduce continuously, yielding smaller clutches, corroborat- ing the hypothesis that environmental conditions exert an important influence upon life-history parameters. There were significant differences in body shape among populations, but most of the variation was related to sex. We also observed signifi- cant differences in body size among populations, seemingly unrelated to differences in community structure, but the highly conservative morphology of Cnemidophorus species suggests the presence of historical constraints. T WO major patterns have been identified in studies of geographic variation in life-his- tory parameters among squamates. On one hand, species may exhibit the same attributes independently of variations in environmental parameters. For example, lizards of the large Neotropical genus Anolis exhibit an unusual re- productive characteristic, all species laying clutches of a single egg. This is compensated for by frequent ovipositions (e.g., Andrews and Rand, 1974; Roff, 1992), a pattern that is likely genetically constrained. Conversely, differences in environmental conditions among sites can lead to differences in life-history patterns among taxa resulting from ecotypical adapta- tions. For example, the Neotropical lizard Amei- va ameiva reproduces seasonally in areas where climate is highly seasonal (Cerrado and Ama- zonian Savannas) but continuously where pre- cipitation is abundant throughout the year (Am- azon Forest) or where climate is unpredictable (Caatinga, Vitt, 1982; Colli, 1991; Vitt and Colli, 1994). The influence of environmental condi- tions upon life-history parameters of squamates has usually been assessed through geographical variation studies (e.g., Tinkle and Dunhan, 1986; Vitt, 1992; Vitt et al., 1998). The genus Cnemidophorus is distributed from the northern United States to central Argentina (Wright, 1993), comprising approximately 50 species (Cole and Dessauer, 1993; Wright, 1993; Rocha et al., 2000). Eight species of Cnemido- phorus are presently known to occur in Brazil: the bisexuals Cnemidophorus lemniscatus and Cnemidophorus gramivagus and the unisexual Cnemidophorus cryptus, in Amazonia (A ´ vila-Pires, 1995); the bisexual Cnemidophorus lacertoides, in the southern region (Peters and Orejas-Miran- da, 1986); the unisexual Cnemidophorus nativo, in the state of Espı ´rito Santo (Rocha et al., 1997); the bisexuals Cnemidophorus littoralis, in the state of Rio de Janeiro (Rocha et al., 2000), Cnemi- dophorus vacariensis, in the state of Rio Grande do Sul (Feltrin and Lema, 2000), Cnemidophorus ocellifer, in the entire territory, except Amazonia (Vanzolini et al., 1980; Peters and Orejas-Miran- da, 1986; Colli, 1998), and Cnemidophorus parecis