A simulation model of the effects of frequency dependence, density dependence and parasitoid flies on the fitness of male field crickets

Abstract

There is substantial variation in the strategies animals use to obtain mates. In crickets, males may call to attract females or use a non-calling, or satellite, strategy and intercept females attracted to the calls of other males. Calling males are subject to attack by an acoustically orienting parasitoid fly and, after being parasitized, males die in 7–10 days. We used a simulation model to determine how frequency dependence, population density, and parasitoid flies affect the mating success of calling and non-calling males. The simulation demonstrated that calling males have higher mating success than satellite males under most conditions, and the fitness of both strategies increases with population density. Frequency-dependent selection did not have strong effects on calling or satellite male fitness. However, if parasitoid flies were present, satellite males had similar or higher mating success than calling males. These results demonstrate that the risk of parasitism strongly influences the fitness of calling and satellite males and likely contributes to the continued coexistence of alternative reproductive behavior in crickets.