Operational Sex Ratios and Mating Conflict between the Sexes in the Water Strider Gerris lacustris

This is the first study to highlight the importance of individual operational sex ratio (OSR) experience in altering mating behavior and intersexual conflict over mating in insects. Reproductively active Gerris lacustris were held under highly male- or female-biased sex ratios and then tested in various treatment combinations with either male- or female-biased sex ratios. With our manipulations we disentangled the effect of experienced and ambient (mating environment) OSR, separately for females and males, which allowed the assessment of the differing contributions of male persistence and female reluctance in mating. Only male OSR experience affected the duration of mating: males from male-biased environments increased the length of copulation and postcopulatory guarding and the proportion of guarding of total duration of mating. Female-biased experience of both sexes resulted in short matings with practically no guarding, and males dismounted before females started struggling. Males from male-biased and females from female-biased environments mated a relatively long time, but 95% of these matings were terminated by the female. Females with female-biased experience resisted mating attempts more vigorously than females with male-biased experience, and males failed to mate more frequently with females from female-biased than with females from male-biased environments. Ambient OSR differences did not affect mating behavior. We conclude that theory on the impact of OSR on mating behavior should be expanded to include OSR experience, especially when males and females come from OSR environments biased toward their own sex.