Background/Question/Methods In disturbed ecosystems, anthropogenic stressors interact with natural stressors to impact both populations and communities.  Specifically, animals living in agroecosystems must cope with a range of anthropogenic stressors that affect their foraging behaviors and interactions with predators.  Foraging success (dependent on prey availability) and responses to predators can in turn impact reproductive fitness.  The goal of our experiments was to determine how a common herbicide (active ingredient glyphosate) interacted with predator cues and prey availability to affect foraging and ultimately reproduction in spiders.  We used the wolf spider Pardosa milvina, a numerically dominant epigeal predator in agricultural systems across the eastern United States.  Pardosa milvina frequently encounter herbicide spray and extreme differences in prey availability across the season, while regularly falling prey to the larger wolf spider, Hogna helluo and/or the carabid beetle, Scarites quadriceps. We exposed P. milvina to all combinations of predator cues (H. helluo, S. quadriceps, or none), herbicide (or water), and prey availability (high or low).  After exposure, we measured foraging success as the number of prey consumed and changes in abdomen width.  We then maintained P. milvina in the laboratory and recorded several measures of reproductive success (e.g. production of viable eggsacs). 

Results/Conclusions Our results demonstrated that in the low feeding treatments, spiders exposed to predator cues were less likely to produce an eggsac at all, whereas spiders exposed to herbicide were less likely to produce a viable eggsac (one that hatched).  Therefore, individuals that are under low food conditions and are exposed to predator cues and herbicide at the same time may have greatly reduced fecundity.  In the high feeding treatment these effects were reversed; spiders exposed to herbicide were slightly less likely to produce an eggsac at all, but spiders exposed to predator cues (specifically S. quadriceps) were less likely to produce a viable eggsac.  Interestingly, in the high feeding treatments, spiders exposed to H. helluo cues seem to have little trouble producing a viable eggsac.  From these results we can conclude that exposure to herbicide and predator cues can create complex interactions which might be mediated by the spider’s foraging success.  These results have implications for the fitness of this common agricultural species, and demonstrate that this herbicide may play a role in food web interactions.