COURTSHIP ROLE REVERSAL IN BUSH-CRICKETS - ANOTHER ROLE FOR PARASITES

The last decade has seen an increasing body of evidence in support of the idea that parasites can play a role in sexual selection. Parasites have been shown to influence mate choice and mating competition. Here I demonstrate a further role for parasites in that they can determine the courtship roles of males and females and thus the sex on which sexual selection acts. Male bush crickets, Requena verticalis, feed their mates during insemination with a nutritious meal, the spermatophylax, that increases female fecundity. I show how the ability of males to donate nutrients was reduced by increased intensities of infection of a protozoan gut parasite. Further, increased intensity of infection reduced female fecundity. Mating trials showed that when females were uninfected the typical courtship roles prevailed; females were the coy, discriminating sex. However, when infected with gut parasites, females attempted to mate more often and males adopted the coy discriminative role in courtship. Thus it appeared that male donations were of greater importance for reproductively constrained, infected females. The infection status of the male had no influence on courtship role reversal supporting the idea that proximate cues in female behavior determine the courtship role adopted by males. It is argued that parasites will be an important determinant of courtship role reversal in any species where male gifts influence female fecundity, and parasites constrain host reproduction, because of the opposing way in which reproductive constraints will influence male and female mating frequency.