Effects of the light environment on courtship displays in multimodal signalling wolf spiders

Light availability is highly variable, yet predictable, over various timescales and plays an important role in the evolution of visual signals. Courtship displays of the wolf spider genus Schizocosa always involve the use of substrate-borne vibrations, however, visual displays vary substantially among species. We tested the function of visual courtship signaling across distinct light environments in four Schizocosa species that vary in their degree of ornamentation and dynamic visual signals. We ran mating and courtship trials at three light intensities and tested the hypothesis that ornamentation interacts with the light environment. We also examined each species’ circadian activity patterns. The effects of the light environment on courtship and mating varied between species as did circadian activity patterns. Our results suggest that femur pigmentation may have evolved for diurnal signaling, whereas tibial brushes may function to increase signal efficacy under dim light. Additionally, we found evidence for light-dependent changes in selection on male traits, illustrating that short-term changes in light intensity have the potential for strong effects on the dynamics of sexual selection.