Infection stress and mate assessment in wolf-spiders: female mate choice varies with sensory mode of male courtship

Fighting infections is energetically costly and can result in resource trade-offs with other life history processes, including reproduction. Studies investigating parasite-mediated sexual-selection have sometimes overlooked the effect of pathogen-induced effects on female choosiness, focusing on costs to the more obvious male secondary sex traits, which include courtship behavior, and subsequent responses of healthy females to infected males. This experimental study examined the trade-offs between infection stress and female mate choice in a well-studied wolf spider. Females are choosey, opting for males displaying condition-dependent traits indicating high mate quality (larger/ more symmetrical tufts of foreleg bristles; production of higher peak amplitude vibratory signals). Female S. ocreata were tested to determine whether recent infection by Pseudomonas aeruginosa, a common bacterium in their habitat, impacts choosiness when presented with video and/or vibratory playback of courting male stimuli with manipulated leg tuft size and vibration amplitude. Three sensory modes were tested (visual, vibratory, or both-multimodal) and three treatment groups were utilized, one infected group and two controls— testing for effects of sham control treatment. The additional unmanipulated control group was later excluded once it was determined that the sham control treatment did not affect behavior. Females were presented with a choice between video or vibration playback of courtship signals of high- and low-quality males (large vs. small foreleg tufts; high vs low peak amplitude of vibratory signals). Female behavior was scored using the number of receptivity displays and time spent visiting either of the two screens within the 5-minute trials. Results show that female receptivity behavior varied based on sensory mode of male courtship and infection treatment. In the visual sensory mode, control females showed significantly greater choosiness than their infected counterparts. These results suggest that infection stress may be impacting the visual sensory pathway more than vibration perception.