Mating with sexually attractive males provides female Gryllus firmus field crickets with direct but not indirect fitness benefits

Abstract

Females choose to mate with certain males to accrue either genetic or direct benefits, and male sexual attractiveness evolved to advertise those benefits to potential mates. Sexually attractive males are expected to be of higher genetic quality and thus possess greater body condition and perhaps greater disease resistance. Positive covariance between male sexual attractiveness and disease resistance should thus provide females an avenue for acquiring genes related to better disease resistance for their offspring. We support the hypothesis that sexually attractive males are in better body condition, but we did not support the hypothesis that they are more disease resistant. Contrary to prediction, the offspring of more attractive males were neither in better body condition nor more disease resistant than the offspring of less attractive males, thus suggesting that females do not gain indirect genetic benefits by mating with attractive males. We supported the hypothesis that females receive more material benefits from mating with more attractive males as females laid more eggs when mated to males having greater sexual attractiveness. The mechanism underlying this effect is unclear at present but could be due to more ejaculatory products (i.e., more sperm or seminal substances) being passed by more attractive mates or due to female processes such as cryptic female choice. Females are generally the choosier sex when it comes to finding mate. Choosiness benefits females because by mating with a preferred, sexually attractive male, females can accrue better or more material resources that they require for breeding or superior genes for their offspring. We experimentally tested whether and how mating with sexually attractive males benefits female sand crickets (Gryllus firmus). In line with prediction, we found that females laid more eggs when they copulated with attractive males rather than unattractive males. Contrary to prediction, however, our tests revealed that the offspring of attractive males were not significantly more disease resistant or more sexually attractive than the offspring of less attractive males. Not surprisingly, we found little evidence of strong heritability in these traits and that daughters of sexually attractive males were no less fit than sons (and vice versa).