Light Environment Interacts with Visual Displays in a Species-Specific Manner in Multimodal-Signaling Wolf Spiders

AbstractLight availability is highly variable, yet predictable, over various timescales and is expected to play 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, there is substantial variation in the presence and complexity of visual displays among species. To gain insight into the role the light environment plays in the evolution of courtship displays, we tested the function of visual courtship signaling across distinct light environments in four species of Schizocosa that vary in their degree of ornamentation and dynamic visual signals. We ran mating and courtship trials at three light intensities (bright, dim, and dark) and tested the hypothesis that ornamentation interacts with 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.