© 1990 by The Society for Integrative and Comparative Biology
Parasites and Mate Choice in Gray Treefrogs, Hyla versicolor1
Division of Biological Sciences, University of Missouri Columbia, Missouri 65211
A fundamental assumption of the Hamilton and Zuk (1982) model of sexual selection is that parasite-free males should produce mate attracting displays that are substantially more vigorous and effective than those of their parasitized counterparts. Further, the model predicts that parasite-free males should be preferred as mating partners by females and, as a consequence, should have higher reproductive success than their parasitized competitors. Gray treefrogs (Hyla versicolor) constitute an ideal species for testing both assumptions and predictions of the Hamilton-Zuk model in that: (i) mate attraction by males requires the production of energetically costly calls and (ii) males of this species have been shown to harbor a wide range of helminth parasites. The present paper summarizes results of analyses of calling and mating behavior by male gray treefrogs in relation to their parasite infection levels. In general, these analyses revealed no consistent relationship between the number and kinds of parasites harbored by males and either the duration or duty-cycle (a direct measure of energetic cost) of their calls. Furthermore, males found in amplexus (i.e., males actually selected as mating partners by females) showed a slightly higher prevalence of parasite infection (but a slightly lower intensity of infection) than did a comparable sample of unmated males. In sum, the present study failed to support the major within-species prediction of the Hamilton-Zuk model of sexual selection and also calls into question one of the fundamental assumptions of the model.