Does season-dependent reproductive value of offspring drive the evolution of life-history traits in Anolis lizards?

Abstract

An important component of the reproductive strategy of many animals involves a seasonal shift in reproductive traits (i.e., clutch size, egg quality). Such shifts typically occur because environmental factors that influence reproduction (i.e., climate or food availability) change throughout the year; thus, organisms must change their reproduction as the environment changes to maximize fitness. Anole lizards are unique among squamates because they lay multiple, successive, single-egg clutches throughout the entire breeding season. As such, a single female can lay eggs approximately once per week for the greater portion of a year. Therefore, these lizards can serve as appropriate models to understand how seasonal changes in the environment interact with a reproductive strategy to maximize fitness. We synthesize the results of multiple lab and field experiments to 1) demonstrate how aspects of anole reproduction change seasonally and 2) discuss how these seasonal shifts may influence fitness. Our preliminary lab results demonstrate that key reproductive traits like egg size, egg quality, and hatchling size can increase through the reproductive season but field experiments suggest survival probability of hatchlings decreases across the same period. Further analyses will quantify variation in other reproductive traits, such as inter-clutch interval, total reproductive effort, and the relationship between this variation and seasonal changes in adult body size. Anoles have often served as model organisms for studies of ecology and evolution. By learning about seasonal shifts in reproduction and their influence on fitness, we will both increase our knowledge of anole natural history and enhance our general understanding of life history theory.