Anthropogenic chemicals have been shown to disrupt chemical communication among many different animals, but most of such studies to date have been conducted in aquatic habitats. The wolf spider Pardosa milvina is a terrestrial arthropod abundant in the agroecosystems of eastern North America, where glyphosate-based herbicides are regularly applied. Mating in P. milvina is mediated by chemical signals; females attract males with an airborne signal, and substrate-borne chemicals from females allow males to assess female quality. In a field experiment, we tested the hypothesis that exposure to a glyphosate–based herbicide (Buccaneer® Plus) would affect mate location in P. milvina. We sequestered virgin females in small containers inside pitfall traps and quantified the number and frequency of males captured after seven hours. Our design included four treatments and a control: two treatments consisted of females’ exposure to either water or herbicide via filter paper substrate while inside the vial; two other treatments consisted of placing a water- or herbicide-laden filter paper ring around the outside of the trap.
Results/Conclusions
Traps containing herbicide-exposed females captured less males than those containing water-exposed females. Traps with a ring of water-treated filter paper surrounding their opening were more likely to capture a male than traps where the ring of filter paper was treated with herbicide. These results suggest that the herbicide reduced the efficacy of female signaling and reduced the likelihood that a male would approach a female. Furthermore, the spraying of herbicide at a critical time in the life cycle of this species could impact the intensity of sexual selection and ultimately their reproductive success in agroecosystems. As this species is an abundant predator in agroecosystems, herbicide application has the potential to exert unintended effects on population and community structure as well as impact the food web.
