Substrate-dependent signalling success in the wolf spider, Schizocosa retrorsa

Abstract

Understanding past as well as present selection pressures that have influenced the origin, evolution and maintenance of existing communication systems presents a considerable challenge to biologists. Among the multitude of factors known to influence signal form, characteristics of the signalling environment play a crucial role. For example, numerous empirical studies have demonstrated a clear effect of signalling habitat on visual signal evolution in fish (Endler, 1991; Endler, 1992; Boughman, 2001; Maan et al., 2006), birds (Marchetti, 1993; Endler and Thery, 1996; Cynx et al., 1998; Lengagne et al., 1999; Lengagne and Slater, 2002; Heindl and Winkler, 2003a; Heindl and Winkler, 2003b;Uy and Endler, 2004), and lizards (Fleishman and Persons, 2001; Macedonia et al., 2003; Peters and Evans, 2003; Leal and Fleishman, 2004). In addition, evidence that air-borne signal evolution is influenced by habitat characteristics is provided by studies involving singing insects (Michelsen and Larsen, 1983; Romer, 1990;VanStaaden and Romer, 1997;Schul and Patterson, 2003), birds (Richards and Wiley, 1980; Ryan and Brenowitz, 1985;Wiley, 1991) and frogs (Ryan et al., 1990; Ryan and Wilczynski, 1991). Fewer studies have assessed habitat-specific effects on the evolution of substrate-borne (seismic) signals (Michelsen et al., 1982; Magal et al., 2000; Cokl and Dober- AbstractSignals used in communication are often hypothesized to be optimally designed for their signalling environment. Here, we explore the importance of signalling substrate on seismic signal efficacy and reproductive behavior in the wolf spider, Schizocosa retrorsa: a species found on multiple signalling substrates (pine litter and/or red clay or sand). In this multimodal signalling species, simultaneous with conspicuous visual displays, males produce percussive seismic signals via an impulse mechanism which tends to excite a substrate evenly across a wide band of frequencies. We first quantified the transmission characteristics of this broadband percussive signal by playing recorded signals back across three naturally occurring substrates, two of which represent substrates upon which S. retrorsa is commonly found: leaf litter, pine litter and red clay (the latter two exemplify their natural habitat). The substrates varied in their transmission characteristics with respect to both attenuation (higher on red clay) and filtering. Next, we compared copulation success, courtship behavior and microhabitat choice among these same substrates. Copulation frequency was higher on the natural substrates of pine litter and red clay as compared with leaf litter. Males took longer to initiate courtship on leaf litter, but once initiated, courtship behavior did not vary across substrates and we were not able to discern any choice with respect to the first, or the most common, substrate chosen. Our results show that while S. retrorsa's percussive signals may not be matched to the specific properties of any one substrate, copulation success was substrate dependent and we d...

Multimodal courtship efficacy of Schizocosa retrorsa wolf spiders: implications of an additional signal modality

“…Schizocosa retrorsa, in contrast, is found mainly on pine litter, red clay, or sand and produces seismic signals via pedipalpal drumming. The seismic signaling substrate is also known to influence copulation success in S. retrorsa as pairs are more likely to copulate on their natural substrates of pine litter and red clay as compared with leaf litter (Hebets, Elias, et al 2008). Although the emerging pattern suggests that the signaling environment has played a major role in shaping courtship form and function for at least some Schizocosa species, with currently available data, we are not yet able to fully elucidate the links between natural signaling substrate, seismic signal production, and seismic signal importance or function across Schizocosa species.…”

Dangerous mating systems: Signal complexity, signal content and neural capacity in spiders

“…In contrast, no relationship was found between vibratory signal complexity and vibratory signal importance and the vibratory signals were hypothesized to be selected for signal efficacy. Indeed, studies on both jumping spiders (Elias et al, 2004) and wolf spiders (Hebets et al, 2008) have demonstrated that the spectral characteristics of the vibratory signal components correspond to low signal attenuation on substrate-types characteristic of their natural signaling environment (e.g. leaf litter), suggesting selection for signal efficacy.…”

“…With the advent of non-contact methods of recording vibrations, such as laser vibrometry, the field has made substantial advances in recent years (e.g. Landolfa and Barth, 1996;Elias et al, 2006;Hebets et al, 2008;Wignall and Herberstein, 2013a).…”

Cuttlefish dynamic camouflage: responses to substrate choice and integration of multiple visual cues

“…Substrate choice can be related to communication and copulation success (e.g. wolf spiders; Hebets et al 2008). Animals make substrate choices as part of antipredator behaviours such as hiding and shoaling (e.g.…”