Title

Wait, don't mate (yet)! Reproductive urgency, not investment underlies female choosiness in Hyla versicolor

Date of Award

2017

Document Type

Restricted Thesis

Terms of Use

© 2017 Brandon L. Bastien. All rights reserved.

Degree Name

Bachelor of Arts

Department

Biology

First Advisor

Alexander T. Baugh

Abstract

Female mate choice is one of the major sources of sexual selection, leading to the evolution of ornate traits and behaviors in males. Female mate choice is thought to be condition dependent, with reproductive condition being a particularly important factor. Furthermore, levels of gonadal and stress hormones have been shown to influence a female's choice for a mate. Females of many species have been shown to exhibit differences in their choosiness, and can vary individually. Here I tested two hypotheses to explain this variation at a proximal level: the reproductive urgency hypothesis that predicts that frogs that are in a more urgent reproductive state will be less choosy, and the reproductive investment hypothesis, which predicts that frogs that have invested less (e.g. smaller egg clutches) in their clutch of eggs will be less choosy. To test these hypotheses, wild female frogs collected in amplexus were repeatedly tested in controlled playback trials using a dynamic mate choice paradigm, where several behaviors were measured during these trials, including components of the mate choice behavior such as latency to choice and time spent stationary. Then, to evaluate if underlying hormonal mechanisms explained variation in the mate choice behaviors, three steroid hormones, estradiol, progesterone, and corticosterone, were collected using a non-invasive water-borne hormone assay. Finally, latency to oviposit their clutch of eggs and the clutch mass were measured to estimate female condition. I found that female frogs that were in a more urgent reproductive state (i.e. closer to oviposition) had lower levels of progesterone and estradiol, and frogs with higher levels of progesterone exhibited choosier behavior. This may be because in a less urgent reproductive state, females have the opportunity to sample more potential mates. Thus, even though a female's reproductive readiness is a transient life history stage, individual differences in this remarkably brief period lead to variation in behavior, suggesting this state provides a potentially important source of heterogeneous source of inter-sexual selection.

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