Appealing but a cheat: choice of attractive but sick males reduces the fitness of females

Abstract

One central tenet in sexual selection theory is that sexual traits are honest indicators of individual condition. This does not appear to be the case for Tenebrio molitor beetles whose males, when infected with the fungus Metarhizium robertsii, produce chemical signals (pheromones) that increase their attractiveness. Using this system, we have investigated the consequences of non-adaptive female choice with regard to: (a) survival of females in choosing fungus-infected males; and (b) whether the number and duration of copulations increases fungal infection in females. Females that mated with fungus-infected males lived half as long as females that mated with infection-free males. In addition, the greater the number and the longer the duration of copulation(s), the greater the fungal sporulation in females, suggesting that the fungus may be mainly transmitted during copulation. This study documents a conflict between the sexes: while the dishonesty of a sexual signal increases male fitness, it reduces female fitness.