NICHE PARTITIONING IN A TROPICAL WET SEASON - LIZARDS IN THE LAVRADO AREA OF NORTHERN BRAZIL

The lavrado area of northern Brazil has a lizard fauna of only eight s pecies, seven of which are carnivorous. Three feeding guilds are appar ent, and these follow taxonomic lines: (I) a herbivore guild; (2) a si t-and-wait foraging guild; and (3) an active foraging guild. The carni vorous species are nonrandomly distributed with respect to habitats an d microhabitats. One relatively rare habitat patch, containing trees, shrubs, and access to temporary aquatic habitats has all seven carnivo rous species. Large-bodied teiid lizards occur at low relative densiti es in other habitats. Activity times are similar among species with mo st lizard activity occurring from late morning through early afternoon . Body temperatures vary among lizard species and, to some degree, are correlated with environmental temperatures but do not translate into differences in time of activity. Temperature differences among species remain when the effect of environmental temperatures on body temperat ures is removed. Active-foraging teiid lizards maintain higher body te mperatures than the sit-and-wait iguanian species. A wide diversity of prey are taken by lizards in the lavrado assemblage, ranging from col lembolans to vertebrates. Active foraging species feed largely on inac tive, clustered, or very large (vertebrates) prey whereas sit-and-wait species feed largely on mobile invertebrates. Diet niche breadths var ied from extremely narrow in the microhabitat specialist Gymnophthalmu s leucomystax to extremely broad in the habitat generalist Cnemidophor us lemniscatus. An electivity analysis on lizard diets identified two species as specialists-both small-bodied species occurring in microhab itats different from other species. Prey overlaps among species were r elatively low although active foraging lizards have diets more similar to each other than to lizards in the sit-and-wait foraging guild. A p seudocommunity analysis revealed structure in the lizard assemblage wh en all positions in the diet data matrix were randomized (scrambled ze ros randomization). When zero positions were retained (conserved zeros randomization), no structure was apparent indicating the importance o f food not eaten in maintaining structure. Guilds were apparent based on nearest neighbor analysis, and these only partially corresponded to guilds identified on the basis of prey acquisition mode.