Mate sampling and the sexual conflict over mating in seaweed flies

The order in which females encounter, or sample, males in a population may have important consequences for mate choice, with the information gathered about males influencing both the preference function and degree of choosiness of females. Sexual selection may be affected as a result. Sampling of particular subsets of males may be a crucial component of individual variation in mate preferences within populations. However, the sequence in which males are sampled may also be important in species without traditional, active mate choice, such as when sexual selection involves sexual conflict over mating. This would occur if the likelihood of a female mating with a male of a certain phenotype changes as a result of previous encounters. We examined the effects of encountering males differing in body size, a sexually selected phenotype, in the seaweed fly Coelopa frigida. Sexual selection occurs in this species as a result of a sexual conflict over mating. We show that the outcome of the sexual conflict is independent of the order in which males are encountered by female seaweed flies, with the overall mating advantage to large males being unaffected. In addition, we explored female preference functions and evaluate the heterogeneity in female willingness to mate. We suggest that consideration of mate sampling theory is valuable when examining mate choice in species in which sexual selection is driven by sexual conflict.