Effects of juvenile and adult condition on long-distance call components in the Jamaican field cricket, Gryllus assimilis Emily M. Whattam * , Susan M. Bertram Department of Biology, Carleton University article info Article history: Received 9 March 2010 Initial acceptance 28 April 2010 Final acceptance 15 September 2010 Available online 25 October 2010 MS. number: A10-00171R2 Keywords: acoustic signal complex signal condition-dependence content efficacy field cricket multiple messages multiple signals redundant signal sexual selection Complex signals may arise through either content- or efficacy-based selection. Content-based signals are thought to evolve because of the information content they provide to the receiver. Such signals may function as multiple messages, each relaying different information or types of information. For example, some signals or signal components may indicate different aspects of condition, or condition at different life stages (quality signals), while others relay information on signaller location, or function in species recognition. Or they may act as redundant signals of overall condition, or as backup signals of the same aspect of condition. Efficacy-based signals are proposed to evolve because of the way in which they influence the production, transmission, reception or processing of the signal. We manipulated juvenile and adult condition in male Jamaican field crickets, Gryllus assimilis, to test whether changes in components of the male’s long-distance acoustic mate attraction signal were consistent with content- or efficacy-based selection. Several call components exhibited condition-dependence, and may be under content-based selection. Interpulse duration, pulse rate and chirp duration appeared to honestly signal juvenile condition, while dominant frequency appeared to signal adult condition. Thus, these signal components appeared to be acting as multiple messages of quality. Pulse number, interchirp duration and chirp rate were highly stereotyped and probably function in species recognition. Call number increased with decreasing condition and was likely under efficacy-based selection. No call components appeared to have the potential to act as redundant signals. Crown Copyright Ó 2010. Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved. Many species possess multiple sexual signals (Møller & Petrie 2002). Despite the prevalence of such signals in nature, the reason for their occurrence remains unclear (reviewed in Candolin 2003). There are several hypotheses regarding the evolution of complex signalling (reviewed in: Candolin 2003; Hebets & Papaj 2005). Some invoke content-based selection, in which signals are proposed to have evolved because of the information content that they provide to the receiver. Others are efficacy-based in that they propose that complex signals have evolved because of the way in which they influence the production, transmission, reception or processing of the signal (Hebets & Papaj 2005). Two widely investigated, content-based hypotheses for the evolution of complex signals are the multiple messages and redundant signals hypotheses (reviewed in: Candolin 2003; Hebets & Papaj 2005). In a recent review, Hebets & Papaj (2005) expanded the multiple message hypothesis to include three alternative hypotheses: quality, quality plus and species recognition. The quality model proposes that each signal relays information about a different aspect of signaller condition, or of condition at a different life stage (Møller & Pomiankowski 1993; Johnstone 1996; Hebets & Papaj 2005). For example, in male bowerbirds, feather ultraviolet-violet brightness and bower quality are corre- lated with endoparasite load and ectoparasite load, respectively (Doucet & Montgomerie 2003). Thus, females can determine the amount of each parasite type a male is carrying by assessing these two traits. The quality plus hypothesis is that one signal, or signal component, gives information on signaller quality, while another signal conveys other information, such as signaller location or territory quality (Hebets & Papaj 2005). Finally, the species recog- nition hypothesis proposes that one signal conveys information on signaller quality, while another signal functions in species recognition. The redundant signals hypothesis has been described in two main ways throughout the literature. Møller & Pomiankowski (1993) proposed that redundant signals each provide indepen- dent estimates of overall condition and that each signal differs in * Correspondence and present address: E. M. Whattam, Simon Fraser University, Department of Biological Sciences, 8888 University Drive, Burnaby, British Columbia V5A 1S6, Canada. E-mail address: emily_whattam@sfu.ca (E.M. Whattam). Contents lists available at ScienceDirect Animal Behaviour journal homepage: www.elsevier.com/locate/anbehav 0003-3472/$38.00 Crown Copyright Ó 2010. Published on behalf of The Association for the Study of Animal Behaviour by Elsevier Ltd. All rights reserved. doi:10.1016/j.anbehav.2010.09.024 Animal Behaviour 81 (2011) 135e144