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Browsing by Author "Ting, Janice J."

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    Condition dependence of male lifespan and calling effort in a field cricket
    (2008) Judge, Kevin; Ting, Janice J.; Gwynne, Darryl T.
    Sexually selected traits are thought to impose survival costs on showy males. Recent empirical work found a negative relationship between male display and survival in a field cricket species (Orthoptera, Gryllidae, Gryllinae) where there is no evidence of a mating bias towards older males. In most species, however, male survival and ornamentation are positively correlated, and older males often have a mating success advantage over younger males. These findings suggest that male quality and survival are positively correlated, but more tests of this hypothesis are needed. We measured the condition dependence of male survival and mating investment (calling effort) in another grylline, Gryllus pennsylvanicus, where older males have previously been shown to have greater mating success. We varied condition by manipulating diet, and measured male lifespan and calling effort to assess the relative condition dependence of these traits. High and medium condition males survived longer than low condition males, and high condition males called more than medium and low condition males. Differences in calling effort among the condition treatments were not apparent early in life, but emerged as males aged. We discuss possible explanations for the differences between our study and contrasting results such as the previous grylline work.
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    Listening to male song induces female field crickets to differentially allocate reproductive resources
    (2017) Ting, Janice J.; Judge, Kevin; Gwynne, Darryl T.
    Differential investment in offspring by mothers is predicted when there is substantial variation in sire quality. Whether females invest more resources in the offspring of high-quality mates (differential allocation, DA) or in the offspring of low-quality mates (reproductive compensation, RC) is not consistent in the literature and both effects can be predicted by theoretical models. In the field cricket, Gryllus pennsylvanicus Burmeister, 1838 (Orthoptera: Gryllidae: Gryllinae), females are attracted more to calling songs of high-quality males than to those of low-quality males. We tested whether females invest reproductive resources differentially based on perceived mate quality. We manipulated female perception of male quality by allowing virgin females to approach a speaker broadcasting either high- or low-quality calling song (high or low calling effort respectively), and then mated them with a randomly chosen male that had been rendered incapable of calling. In the week following mating, females exposed to high-quality calling song gained less weight, laid more embryos, and laid larger embryos than females exposed to low-quality calling song, although only the first of these effects was statistically significant. These results support the DA hypothesis and suggest that females invest their reproductive output based on a trait (calling effort) that is an honest indicator of male quality.