Bacterial infection and mate choice in a wolf spider

Infection and parasitism are serious risks that can influence condition-indicating ornamental male traits and subsequently inform female mate choice. This paper summarizes recent experiments investigating the relationship between infection stress, male courtship, female choice and parasite avoidance behaviors. We studied the Brush-legged Wolf Spider, Schizocosa ocreata, whose mating behavior, consisting of complex male courtship and female mate choice, highlights complex evolutionary conflict between the sexes at adulthood. Male and female S. ocreata were experimentally infected with the bacterial pathogen Pseudomonas aeruginosa and placed together in triad mating trials wherein one female—either infected or not (control) - was paired with two males—one infected and one control (uninfected). Results showed that control (uninfected) females chose to mate significantly more often with control (uninfected) males than infected males. Infected females, on the other hand, chose infected and control males with equal frequency, suggesting a potential cost of being infected for females—reduced infection avoidance. Male courtship display rates (“bounces”) were higher overall in the group of control (uninfected) males. Furthermore, control males presented with an infected focal female displayed significantly reduced rates of courtship when compared to a control (uninfected) focal female. These results confirm that infection stress has observable impacts on mating success and behavior, but also suggests that the costs of infection may be more subtle than expected and present themselves in ways that are not as dramatic as might be predicted.