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SnowbirdIntegrative Biology and Evolutionary Diversity in the Junco$
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Ellen D. "Ketterson and Jonathan W. Atwell

Print publication date: 2016

Print ISBN-13: 9780226330778

Published to Chicago Scholarship Online: September 2016

DOI: 10.7208/chicago/9780226330808.001.0001

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PRINTED FROM CHICAGO SCHOLARSHIP ONLINE (www.chicago.universitypressscholarship.com). (c) Copyright University of Chicago Press, 2019. All Rights Reserved. An individual user may print out a PDF of a single chapter of a monograph in CHSO for personal use.date: 22 October 2019

Individual Variation and Selection on Hormone-Mediated Phenotypes in Male and Female Dark-Eyed Juncos

Individual Variation and Selection on Hormone-Mediated Phenotypes in Male and Female Dark-Eyed Juncos

Chapter:
(p.120) Chapter Six Individual Variation and Selection on Hormone-Mediated Phenotypes in Male and Female Dark-Eyed Juncos
Source:
Snowbird
Author(s):

Kristal Cain

Jodie M. Jawor

Joel W. McGlothlin

Publisher:
University of Chicago Press
DOI:10.7208/chicago/9780226330808.003.0006

Much of our knowledge of hormones and life histories in animals derives from experimental studies. Complementing experiments with studies of natural (co)variation in hormones and hormone-mediated traits can lead to a richer understanding of the role of hormones in the evolutionary process. Here, we review our work on natural variation in testosterone production and its relationships to hormone-mediated traits and fitness in male and female juncos. To assess variation in testosterone production, we used injections of gonadotropin-releasing hormone (GnRH), which induce repeatable measures of an individual’s ability to produce testosterone. Testosterone production stimulated by GnRH was associated with hormone-mediated behaviors such as aggression and parental care, as well as morphology and several components of fitness. Some of these relationships mirrored the results of experimental manipulations and some did not; possible reasons for the differences are discussed. This research provides an intriguing glimpse of how selection may shape variation in hormones and hormone-mediated phenotypes in natural populations.

Keywords:   Gonadotropin-releasing hormone, GnRH, testosterone, aggression, parental care, individual variation, GnRH challenge, Dark-eyed junco

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