An Introduction to the Ecology of Cerrado Lizards

Abstract

Nine species of lizards are sympatric in cerrado habitats in the state of Mato Grosso, Brazil, including one polychrid (Anolis meridionalis), three tropidurids (Tropidurus etheridgei, T. cf. montanus, and T. spinulosus), one scincid (Mabuya frenata), two teiids (Ameiva ameiva and Cnemidophorus ocellifer), and two gymnophthalmids (Micrablepharus maximiliani and Pantodactylus schreibersii. Lizard diversity is lower than that reported for caatinga or lowland rainforest. Most striking in the cerrado lizard fauna is the lack of gekkonids, which are common in other Brazilian habitats studied. The Iguania clearly separate by microhabitat, and microhabitat differences are partially reflected in diets. There is little similarity in habitat use by the primarily arboreal Iguania and the strictly terrestrial teiids and gymnophthalmids. Teiids and gymnophthalmids often occur in the same microhabitats, but the large differences in size among species generally result in utilization of different prey types and/or sizes. Ameiva ameiva and Cnemidophorus ocellifer are very similar in habitat use and prey types, but do not overlap in body size and take prey of very different sizes. Electivity analysis of prey volumes suggests sample size bias as well as a bias based on lizard body size differences. The largest species, A. ameiva, accounts for most of the prey taken by the lizard assemblage. Eight of the nine species are oviparous; the other, Mabuya frenata, is viviparous with extended gestation and typical South American Mabuya matrotrophy. As in other Brazilian lizard assemblages studied, a diversity of life history patterns is evident with each species being more similar to closely-related species in distant and different habitats than to unrelated sympatric species. The cerrados represent one of the largest vegetational zones of South America, extending from southern Brazil to the Amazon Basin and totaling about 1,500,000 km2 (Ferri, 1977). In addition, there are isolated patches north of the Amazon Basin. Cerrados consist of a patchwork of at least four macrohabitats: campo, cerrado, cerradao, and gallery forest (Eiten, 1972), which vary in the size, density, and types of trees. Campo (which means field) contains the lowest density of trees or no trees. Cerrado proper is the most widespread vegetation type in the cerrados, consisting of extensive grasslands covered by varying densities of xeromorphic trees but with an open canopy. The trees appear twisted, have thickened bark usually showing evidence of fire, and the leaves are leathery. Cerradao contains larger trees and the canopy is generally closed or nearly so. Trees may exceed 10 m. Gallery forest (bands of tropical forest along water courses) contains the largest trees and displays a closed canopy. In addition, there are transitional zones between each of these (Eiten, 1975). The most prominent climatological feature of the cerrados is the dry winter (Vanzolini, 1972). Cerrados differ from savannas in containing a permanent deep water table 1 Present Address: Oklahoma Museum of Natural History, University of Oklahoma, Norman, Oklahoma 73019, USA. and deep non-stoney, non-lateritic soils (Eiten, 1972). Considering the extensive distribution of the cerrados in South America, it is surprising that there have been no ecological studies of the liza d assemblages inhabiting them since Vanzolini (1948) first described the squamate assemblage in a cerrado site in the state of Sao Paulo. Indeed, the best available data consist of field observations on individual species (Vanzolini, 1972, 1986), general ecological descriptions in taxonomic studies (e.g., Rodrigues, 1987), comments on the origin and biogeography of cerrado faunas (Vanzolini, 1963, 1976), and more recently, studies of individual species (Colli, 1991). Because of the vast distribution of cerrados, the potential exists to examine the influence of climatic and vegetation gradients on the structure of lizard assemblages. In addition, it should be possible to examine interactions between different lizard assemblages where cerrado contacts lowland Amazonian forest to the north, Atlantic rain forest to the east, the Chaco to the southwest, Andean foothills to the west, and semi-arid caatingas to the northeast. Patterns of alpha, beta, and gamma diversity (Cody, 1975) might be particularly instructive considering these major habitat contacts. Vanzolini (1974), for example, has shown that contact zones provide critical information necessary for understanding the ecology and biogeography of Brazilian lizards. This content downloaded from 207.46.13.131 on Sat, 15 Oct 2016 04:27:20 UTC All use subject to http://about.jstor.org/terms