Female mate choice for multimodal courtship and the importance of the signaling background for selection on male ornamentation

Abstract

Conspicuous visual ornaments are frequently incorporated into complex courtship displays that integrate signal components from multiple sensory modalities. Mature male Schizocosa crassipes (Walckenaer, 1837) wolf spiders wave, arch, and tap their ornamented forelegs in a visual courtship display that simultaneously incorporates seismic components. To determine the importance of modality-specific signal components in female mate choice, we used a signal ablation design and compared the mating frequency of female-male pairs across signaling environments with manipulated modality-specific transmission properties. We found that the successful transmission of isolated visual or seismic signaling was sufficient for mating success; neither signaling modality was necessary. Additionally, the environment enabling the successful transmission of composite, multimodal displays yielded the highest mating frequencies. Our results indicate the presence of selection from S. crassipes females for multimodal courtship and suggest that multimodal signaling may facilitate mating across variable signaling environments. We next explored the influence of ornamentation per se on female choice by phenotypically manipulating males into two groups: (i) intact (brushes present) and (ii) shaved (brushes absent). We compared the mating frequencies of intact versus shaved males in the presence versus absence of seismic signaling. Males with brushes intact had higher mating frequencies than shaved males, but only under specific signaling conditions - in the presence of seismic signaling. Female choice for male brushes then appears dependent on the signaling background, making brushes themselves an unlikely target of direct selection. Our results emphasize the complex nature of female choice, highlighting the potential for both trait interactions and environment-dependent selection [Current Zoology 59 (2): 200-209, 2013]. © 2013 Current Zoology.