Postdoctoral Fellow

Expanded Bateman Gradients: a synthetic refinement of sexual selection theory

PI(s): Courtney L Fitzpatrick
Start Date: 1-Jan-2013
End Date: 1-Dec-2014
Keywords: sexual selection, mathematical modeling, evolutionary theory, behavior

Sexual selection has been one of the most heavily investigated evolutionary processes since Darwin proposed it as a mechanism of evolution in 1871. The process of sexual selection has traditionally been modeled as fitness differences mediated through variation in mating success (VMS). However, empirical studies increasingly find exaggerated sexual traits in individuals that appear to experience little VMS (for instance, in females of a number of species). Despite the unidentified (or absent) VMS, these traits are often posited to be under sexual selection. One explanation is that sexual selection may sometimes be mediated through variation in mate quality (VMQ) rather than only through variation in the number of mates (VMS). However, we lack a formal theoretical foundation for sexual selection in these cases. This disconnect hinders the forward progress of empirical studies, particularly those studies that investigate sexual selection in females, because an increase in the number of mates will often not confer a fitness advantage to females. That is, current models do not address whether or not we should expect sexual selection pressure when VMS = 0 or when VMS does not drive variation in fecundity. Therefore, the formal investigation of sexual selection in these cases is stalled until an expanded model of sexual selection is generated that can accommodate fitness benefits that are mediated through mate quality. This project proposes to generate a unified theoretical model of sexual selection, by expanding the conceptually powerful “Bateman gradient” framework to include VMQ as a potential “fitness currency” of sexual selection.