Independence of Sexual and Anti-Predator Perceptual Functions in an Acoustic Moth: Implications for the Receiver Bias Mechanism in Signal Evolution Michael D. Greenfield* & Hannah Hohendorf  * L’Institut de recherche ´ sur la biologie de l’insecte, CNRS UMR 6035, Universite ´ Franc ¸ ois Rabelais de Tours, Tours, France  Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA Introduction It is generally proposed that the various components of animal communication systems may originate in activities outside the realm of communication (Hauser 1996; Bradbury & Vehrencamp 1998). For example, perception of, and specific sensitivity to, stimuli may evolve in the contexts of food or habitat localization or the avoidance of predators. Later, these responses may be ‘co-opted’ for mating Correspondence Michael D. Greenfield, L’Institut de recherche sur la biologie de l’insecte, CNRS UMR 6035, Universite ´ Franc ¸ ois Rabelais de Tours, Parc de Grandmont, 37200 Tours, France. E-mail: michael.greenfield@univ-tours.fr Received: March 23, 2009 Initial acceptance: August 12, 2009 Final acceptance: August 12, 2009 (J. Kotiaho) doi: 10.1111/j.1439-0310.2009.01700.x Abstract The receiver bias model for the evolution of mating signals proposes that selection favors male displays that happen to stimulate a general, ances- tral perception in females such that receptivity and successful courtship increase. If these male signals do arise, however, the female perception will operate in two contexts, the original, typically non-sexual, one and courtship. We may then ask whether these two functions represent the same or distinct traits, which may be under separate neural and genetic control. We studied this question in Achroia grisella, a pyralid moth spe- cies in which males attract females, with an ultrasonic mating song. Hearing in pyralid moths is widespread and originated in an anti-preda- tor context – the perception and avoidance of echolocating bats – and it is inferred that the male song found in A. grisella, and in several other pyralid species, arose subsequently via a receiver bias mechanism: Females perceiving male-produced ultrasound and responding with anti-predator behavior normally exhibited in the presence of bat echolo- cations may have inadvertently increased the likelihood of successful courtship. We measured hearing responses in both sexual and anti-pred- ator contexts in inbred lines developed from an A. grisella population. Significant inter-line variance was observed for sensitivity thresholds for female response to male song and for both female and male responses to synthetic bat echolocation signals. Female responses to male song and to synthetic echolocations differed markedly in sensitivity, and the med- ian sexual and anti-predator responses in the various lines were not cor- related. However, a higher level of similarity occurs between the female and male anti-predator responses. Thus, genetic variance for sexual and anti-predator responses appears to exist, and the two responses may rep- resent independent traits. These results imply that when male signals originate via a receiver bias mechanism, female perception does not nec- essarily remain fixed in its ancestral state but has the potential for continued modification. Ethology Ethology 115 (2009) 1137–1149 ª 2009 Blackwell Verlag GmbH 1137 ethology international journal of behavioural biology