Love will tear you apart: different components of female choice exert contrasting selection pressures on male field crickets

Female mate choice is a driving force in the evolution of male secondary sexual characters. It can be dissected into several components: discrimination describes the degree to which females distinguish male trait variation, responsiveness indicates the speed or likelihood of females' reactions to a mate, and preference functions illustrate how the probability of mating relates to male trait variation. Relatively little is known about how these components interact to produce final mating decisions and influence the strength and direction of sexual selection, so I used female field crickets (Teleogryllus oceanicus) to measure interactions between individual preference functions, discrimination, and 2 measures of responsiveness (number of responses and response effort). Preference function shape varied considerably between individual females. Highly discriminating females showed greater numbers of responses to playbacks and were more likely to have stabilizing preference functions. When I constructed 2 population-level preference functions using either response number or response effort, the first yielded a linear, directional function, whereas the second implied a stabilizing function. The clear differences between the 2 imply that different components of female choice can exert contrasting selection pressure on a single male trait. Overall, both response number and discrimination were mutually reinforcing and likely govern the strength of sexual selection in this population. The direction of selection in a wild setting ultimately depends on the relative importance of response number versus response effort, where exogenous factors such as predation risk or density will determine which component of female choice predominates mating decisions.