A field and enclosure study of population dynamics and the effects of density on fecundity of Anolis carolinensis and Anolis sagrei (Sauria: Polychrotidae) in conspecific and heterospecific groups

Abstract

Populations of the lizard species Anolis carolinensis in Florida have declined with the spread of the invading Anolis sagrei. This phenomenon appears to be accentuated by habitat disturbance. I conducted an observational field study to investigate the population dynamics of the two species in undisturbed areas of Florida. The main objective of the study was to measure seasonal dynamics in the relative densities of juveniles and adults in allopatric and sympatric populations of the two species in these vegetationally complex habitats. The results of this study led me to design and conduct an outdoor enclosure experiment to investigate the possible effect each of these two species has on the reproduction of the other, and what relationship density has to the interaction. My field study demonstrated that juvenile densities of A. carolinensis appear to be reduced in the presence of A. sagrei in these habitats, suggesting an impact of A. sagrei upon A. carolinensis juveniles in structurally complex habitats. I hypothesised that the mechanism of this reduction in juvenile densities of A. carolinensis is operating at the level of female reproductive output, including the possibility of reduced egg production, reduced egg quality, or both