I am interested in the evolution of reproductive communication systems. There are many factors that can influence the evolution of these systems, such as preferences for signal traits, eavesdropping by predators and parasites, environmentally-induced variation of signals and preferences (i.e. developmental plasticity), and acoustic properties of the habitat, to mention a few. I have been investigating some of these factors in the acoustic communication systems of insects and anurans.

At the University of Nebraska-Lincoln, I am testing the effect of parasitism on the evolution of female preferences for male call traits with Dr. William E. Wagner. Males typically produce conspicuous calls to attract (silent) females and females express preferences for certain call properties. However, these conspicuous male calls are not only used by females but can also be exploited by eavesdropping predators or parasites to locate the signaler. Thus, females associating with conspicuous males are also at risk of encountering predators or parasites that are attracted by calling males.

Males of the cricket Gryllus lineaticeps are parasitized by the acoustically orienting fly Ormia ochraceae (Wagner 1996). Flies have the same preferences for male call properties as female crickets (i.e. they prefer faster chirp rates and longer chirp durations; Wagner 1996), increasing the risk of female crickets of being parasitized when associating with preferred males (Martin & Wagner, in prep.). We will compare parasitized and unparasitzed populations of G. lineaticeps to investigate the influence of parasitism on the evolution of female preferences for male call traits.

As a Ph. D. student at the University of Missouri, I worked with Dr. Johannes Schul on the evolutionary significance of developmental plasticity in the communication system of the katydid Neoconocephalus triops. In North America, this species produces different call phenotypes in different seasons (i.e. summer and winter call phenotype) as a result of developmental plasticity. In the tropics, where N. triops originated, males only produce the summer call phenotype. We found that tropical populations of N. triops already have the developmental plasticity for male calls, but do not experience the environmental conditions inducing the expression of the winter call phenotype. When N. triops moved to temperate North America, environmental conditions induced not only the expression of the summer call phenotype but also the winter call phenotype. We found that in North America female preference evolved in response to this seasonal variation of male calls to match the summer call at high temperatures and the winter call at low temperatures (Beckers & Schul in review). Thus, male call plasticity seems to have driven the evolution of female preferences in temperate populations of N. triops.

Beckers, O.M. and Schul, J. In preparation. Female preferences evolved to compensate for expressed plasticity of male calls in Neoconocephalus triops (Orthoptera: Tettigoniidae).

Bush, S.L., O. M. Beckers, and J. Schul. 2009. A complex mechanism of call recognition in the katydid Neoconocephalus affinis (Orthoptera: Tettigoniidae). Journal of Experimental Biology 212: 648-655.

Beckers, O. M. and J. Schul. 2008. Developmental plasticity of mating calls enables acoustic communication in diverse environments. Proceedings of the Royal Society of London B 275: 1243-1248.

Beckers, O. M. and J. Schul. 2004. Phonotaxis in Hyla versicolor (Anura: Hylidae): the effect of absolute call amplitude. Journal of Comparative Physiology A 190: 869-876.