Exploring a novel substrate-borne vibratory signal in the wolf spider Schizocosa floridana

Animals communicate using a diversity of signals produced by a wide array of physical structures. Determining how a signal is produced provides key insights into signal evolution. Here, we examine a complex vibratory mating display produced by male Schizocosa floridana wolf spiders. This display contains three discrete substrate-borne acoustic components (known as thumps, taps, and chirps), each of which is anecdotally associated with the movement of a different body part (the pedipalps, legs, and abdomen respectively). In order to determine the method of production, we employ a combination of high-speed video/audio recordings and SEM imaging of possible sound-producing structures. Previous work has suggested that the chirp component is tonal, a signal trait that would be potentially unique in the genus. We measured signal tonality for all courtship components, as well as for courtship components from sixteen other Schizocosa wolf spiders. Our results suggest that S. floridana produces courtship song using a combination of shared (palpal stridulation and foreleg percussion) and novel (abdominal movement) sound production mechanisms. Of particular interest, the chirp, which is produced using a novel abdominal production mechanism, is the only known tonal signal with acoustic properties that are unique within the genus. We argue that the potential evolution of a novel sound production mechanism has opened up a new axis of signaling trait space in this species, with important implications for how this signal is likely to function and evolve.

Automated summary

Animals use a variety of signals for communication, and understanding how these signals are produced can provide insights into signal evolution. In the case of male Schizocosa floridana wolf spiders, research has shown that they use a combination of shared and novel sound production mechanisms during their mating displays, including a unique tonal signal.