Abstract
Organisms sometimes appear to use extravagant traits, or “handicaps”, to signal their quality to an interested receiver. Before they were used as signals, many of these traits might have been selected to increase with individual quality for reasons apart from conveying information, allowing receivers to use the traits as “cues” of quality. However, current theory does not explain when and why cues of individual quality become exaggerated into costly handicaps. We address this here, using a game‐theoretic model of adaptive signalling. Our model predicts that: (1) signals will honestly reflect signaler quality whenever there is a positive relationship between individual quality and the signalling trait's naturally selected, non‐informational optimum; and (2) the slope of this relationship will determine the amount of costly signal exaggeration, with more exaggeration favored when the slope is more shallow. A shallow slope means that a lower quality male would pay only a small fitness cost to have the same trait value as a higher quality male, and this drives the exaggeration of signals as high‐quality signalers are selected to distinguish themselves. Our model reveals a simple and potentially widespread mechanism for ensuring signal honesty and predicts a natural continuum of signalling strategies, from cost‐free cues to costly handicaps.
Highlights
Why do some organisms have such bizarre and extravagant traits like the peacock’s tail? Our current understanding is that these traits are probably used to signal an individual’s quality to an interested receiver
The model will apply to analogous contexts, including offspring signalling their need to parents (Godfray 1991; Wild et al 2017) and plants signalling their quality to pollinators or herbivores (Archetti and Brown 2004; Knauer and Schiestl 2015)
We asked how biological signals will evolve from traits with a non-informational optimum that increases with individual quality
Summary
Why do some organisms have such bizarre and extravagant traits like the peacock’s tail? Our current understanding is that these traits are probably used to signal an individual’s quality to an interested receiver (e.g., a peacock’s quality to a peahen). A classic example is the peacock’s tail because it seems so clearly exaggerated beyond what could be useful for flight or any other function beyond attracting mates (Darwin 1871) In such cases, the extravagance of signals may convey honest information about male quality because low-quality males would not benefit from faking an extravagant signal (the handicap principle; Zahavi 1975; Grafen 1990a; Maynard Smith and Harper 2004; Searcy and Nowicki 2005; Bradbury and Vehrencamp 2011). One relevant empirical study suggests that the optimal tail length of male barn swallows, in terms of maximizing aerodynamics, conveys almost all of the information needed to assess their potential quality as mates (Bro-Jørgensen et al 2007) This underscores the basic question: if signals evolve from traits that already reflect individual quality, when and why do they become exaggerated at all?
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
