Genotype–environment interaction and the reliability of mating signals

Abstract

I t is a central tenet of animal communication theory that signals are reliable (Zahavi 1977). That is, the characteristics of a signal that are attended to by a receiver should be reasonably good predictors of the transmitter’s current physical ability, internal state or motivation, social status, or acquired information. Signal characteristics should also predict the future consequences that a receiver, responding in a particular way, is likely to experience. Whereas the range of signals that animals transmit between one another may certainly include some messages that are not fully honest (Hasson 1994; e.g. Backwell et al. 2000), and partially withholding information or identity can sometimes be in a transmitter’s best interest (Johnstone 1997), animal communications are generally expected to result in a net benefit to both signaller and receiver (see Hauser 1996; Bradbury & Vehrencamp 1998). This expectation rests on the reasoning that failure to meet the criterion of reliability, as when an ‘inferior’ individual broadcasts a ‘strong’ signal normally associated with superior physical prowess, should result in selection against receiver responses to the signal, which, in turn, would select against its continued transmission, without alteration, by the signaller. In terms of perfection, signal characteristics are expected to be reliable to the extent that an ‘ideal receiver’, one suffering no perceptual impairments, can respond in a manner that on average enhances its fitness (see Johnstone & Grafen 1993). Within the realm of sexual selection, animal mating signals are expected to indicate the signaller’s phenotype with some degree of reliability. Moreover, under the various coevolutionary mechanisms of sexual selection (wherein mate choice only yields indirect, genetic benefits), mating signals are also expected to indicate the signaller’s genotype and, more critically, the phenotype of offspring that the signaller would sire. This latter expectation is most apparent in those processes