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(mathematically formalized in, e.g., Smith and Fretwell, 1975; Lloyd, 1987; McGinley et al., 1987). Correlational and experimental studies of this trade-off largely support the assumptions of these theoretical models; namely, that propagule size varies inversely as a function of clutch size (Sinervo and Licht, 1991; Landwer, 1994; Doughty and Shine, 1997). Although there is agreement between theoretical models and empirical patterns for a trade-off between offspring size and number from moderate to large clutch sizes (i.e., mean

Lizards with invariant clutch sizes offer an ideal opportunity to examine the effects of "fixed" clutch size on other reproductive traits. Because females with invariant clutch sizes are unable to increase offspring number even when sufficient space and energy are available, females may compensate by laying larger eggs or increasing reproductive frequency. I studied the reproductive biology of Oedura lesueurii, a diplodactyline gekkonid lizard that lays two parchment-shelled eggs per clutch once per year. Eggs of gravid 0. lesueurii females occupied most of the available space in the lower abdomen, and relative clutch masses were moderately large and similar to those of other diplodactyline geckos for which data are available. Measures of female body size (snout-vent length, mass) were correlated with several measures of egg and hatchling size, but not with energetic content on a per-gram basis. Pelvic constraints on maximum egg size and body volume constraints on reproductive output (females can only increase egg size) may account for positive female-offspring size correlations in 0. lesueurii and some other species of lizards with invariant clutch sizes, but more experimental and comparative work on such species is needed. It is possible that more realistic and predictive life-history models of the evolution of propagule size can be achieved by explicitly incorporating specific life-history features of organisms, such as the positive correlations between female size and propagule size in 0. lesueurii and other species of lizards with invariant clutch sizes.

Hatchling dispersal was measured from 1989-1991 in two populations of the side-blotched lizard, Uta stansburiana, in central California. Hatchlings from eggs incubated in the laboratory were released on site and were recaptured throughout the summer and the following spring. Median dispersal was approximately five times greater at Los Banos than at Del Puerto Canyon, and was likely due to different spatial distributions of microhabitats. Body size did not affect dispersal distance at either site despite an experimental increase in the range of hatchling body sizes. At Del Puerto Canyon in the summer, dispersal distances were greater in males than in females, but were not affected by the time of hatching. At Los Banios in the summer, dispersal distances were greater in males and late season hatchlings. Most trends were not significant in the spring at either site. Overall, there were large overlaps in dispersal distributions for all factors studied indicating a large stochastic component to lizard dispersal. Natal dispersal can have profound effects on an individual's survival, reproductive success, and the avoidance of competition and inbreed- ing (Dobson and Jones, 1985; Blouin and Blouin, 1988; Johnson and Gaines, 1990). Although there have been some reports on lizard dispersal (e.g., Andrews and Rand, 1983) and homing behavior (e.g., Ellis-Quinn and Simon, 1989), little data exist on the distances that lizards disperse from their area of hatching or birth. We measured dispersal in the side-blotched lizard, Uta stansburiana, to examine factors that could influence natal dispersal in a territorial lizard species. In this paper we discuss the ef- fects of habitat, time of hatching, and body size on the dispersal of hatchling lizards. We used two novel techniques to investigate neonatal dispersal. First, a release-recapture method was used that enabled us to know the true starting point of dispersal. Second, recent developments in experimental embryology enabled us to ma- nipulate hatchling body size (Sinervo, 1990; Si- nervo and Licht, 1991), and these procedures were used to increase the variation in hatchling body sizes to determine if body size affects dis- persal.