Meeting Abstract
Costs of reproduction structure important evolutionary tradeoffs in males and females, but we lack a general framework for comparing these sex-specific costs and integrating them into a holistic view of life-history evolution. Conceptually, this is due to the historical separation of research on life-history evolution, which has focused primarily on females, versus sexual selection, which has focused primarily on males. Empirically, this is because the primary costs of reproduction are often measured in different currencies, occur at different times, and encompass different regulatory processes in each sex. A first step towards integration between sexes is the measurement of reproductive costs in common currencies, particularly energy and fitness. Recasting the immunocompetence handicap hypothesis in an energy-based perspective illustrates the potential limitations of viewing costs of reproduction through mechanisms that are sex-specific, especially when the tradeoffs that structure such costs are generalizable to either sex. Likewise, sexual conflict theory shows how genetic correlations between the sexes can constrain the evolution of optimal solutions to reproductive tradeoffs within each sex, emphasizing the importance of integration in units of fitness. In these and other cases, a more informative framework could be established by focusing on downstream regulatory axes that are shared between the sexes, and through experiments that abolish the sex-specific aspects of reproductive investment. This approach is illustrated by a series of experiments exploring the mechanistic underpinnings and fitness consequences of reproductive costs in the brown anole (Anolis sagrei). Taken together, these ideas form the basis of a more general framework for integrating theory on life-history evolution and sexual selection by focusing explicitly on the interaction of reproductive tradeoffs in both sexes.
