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Document Type

Grand Teton National Park Report

First Page

39

Last Page

42

Abstract

Few studies have measured multivariate sexual selection acting on the sexual signals of male insects in wild populations. Sagebrush crickets are ideally suited to such investigations because mating imposes an unambiguous phenotypic marker on males arising from nuptial feeding by females. However, an important assumption underlying such studies is that males collected as virgins and those collected as non-virgins had equal opportunities to mate, an assumption that may be violated if males eclose (i.e. emerge following pupation) at different times of the breeding season. If mated males are those in the population that eclosed earlier and hence had a longer period to obtain matings than males in the virgin group, then differences in the songs of virgin and mated males could simply be an artifact of age-related changes in male morphology as opposed to a causal factor underlying variation in male mating success. Accordingly, we conducted a mark-recapture study to determine if there is an association between first appearance in the population and the likelihood of mating in free-living males. We captured all of the virgin males calling in the study population and marked them uniquely with a numbered tag. Subsequently, we tracked the mating success of 98 male subjects through the mid-point of the breeding season. There was no significant effect of date of capture (a proxy for time of eclosion) on time to mating. We conclude, therefore, that any differences in the songs of virgin and mated males stems from their effect on male mating success and not from any age-related effects.

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