Seasonal and individual variation in response to GnRH challenge in male dark-eyed juncos (Junco hyemalis)

Jawor, Jodie M.; McGlothlin, Joel W.; Casto, Joseph M.; Greives, Timothy J.; Snajdr, Eric; Bentley, G.; Ketterson, Ellen D.

doi:10.1016/j.ygcen.2006.05.013

Cited by 134 publications

(169 citation statements)

References 51 publications

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“…Jawor et al [26] found that in dark-eyed juncos, the androgen response to GnRH was repeatable within individuals and While et al [47] found repeatable baseline testosterone levels in individuals of the Australian lizard (Egernia whitii ). These findings raise the possibility that differences in baseline and/or maximum testosterone levels are related to individual differences in behaviour.…”

Section: Discussionmentioning

confidence: 99%

Ignoring the challenge? Male black redstarts ( Phoenicurus ochruros ) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone

Apfelbeck

Goymann

2011

Proc. R. Soc. B.

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Competition elevates plasma testosterone in a wide variety of vertebrates, including humans. The 'challenge hypothesis' proposes that seasonal peaks in testosterone during breeding are caused by social challenges from other males. However, during experimentally induced male -male conflicts, testosterone increases only in a minority of songbird species tested so far. Why is this so? Comparative evidence suggests that species with a short breeding season may not elevate testosterone levels during territory defence. These species may even be limited in their physiological capability to increase testosterone levels, which can be tested by injecting birds with gonadotropin-releasing hormone (GnRH). We studied two populations of black redstarts that differ in breeding altitude, morphology and the length of their breeding season. Unexpectedly, males of neither population increased testosterone in response to a simulated territorial intrusion, but injections with GnRH resulted in a major elevation of testosterone. Thus, black redstarts would have been capable of mounting a testosterone response during the male -male challenge. Our data show, for the first time, that the absence of an androgen response to male -male challenges is not owing to physiological limitations to increase testosterone. Furthermore, in contrast to comparative evidence between species, populations of black redstarts with a long breeding season do not show the expected elevation in testosterone during male -male challenges.

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Section: Discussionmentioning

confidence: 99%

Ignoring the challenge? Male black redstarts ( Phoenicurus ochruros ) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone

Apfelbeck

Goymann

2011

Proc. R. Soc. B.

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“…season, yet the increase in plasma T in response to GnRH injection is greater at the beginning that towards the end of the breeding season (Jawor et al, 2006). In captive male Cassin's Sparrows, administration of the GnRH secretagogue NMA to photostimulated birds with high plasma LH had little effect on the plasma concentrations of this hormone (Deviche et al, 2008).…”

Section: Juncos Junco Hyemalis Have Similar Plasma T Concentrationsmentioning

confidence: 93%

“…The functionality of the HPG axis can be evaluated by measuring hypothalamic gonadotropin-releasing hormone (GnRH-I), the plasma luteinizing hormone (LH) response to administration of GnRH-I or the secretagogue N-methyl-D,L-aspartate (NMA), and by measuring the plasma T response to LH (Dawson, 2005;Deviche et al, 2010) or GnRH (Jawor et al, 2006;Spinney et al, 2006) administration. For example, in male Cassin's Sparrows, Peucaea carpalis, the increase in plasma LH in response to NMA injection is less when birds are photostimulated and have elevated plasma LH than when they are exposed to short days and have low plasma LH (Deviche et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback

Deviche

Sharp

Dawson

et al. 2012

Hormones and Behavior

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“…From 4 to 26 March, we took weekly measurements of subcutaneous fat and cloacal protuberances (CPs). Each week we also measured circulating testosterone, followed by an injection with a standardized dose of gonadotropin releasing hormone (GnRH), which is an established method for assessing a male's ability to produce a short-term increase in testosterone [13]. Extensive prior work using 'GnRH-challenges' to study reproductive ecology and behaviour in juncos found no evidence for lingering physiological or behavioural effect beyond the initial and transient (approx.…”

Section: Methodsmentioning

confidence: 99%

“…30 min.) stimulation [13]. On 31 March and 1 April, we euthanized birds using a lethal dose of isoflorane.…”

Section: Methodsmentioning

confidence: 99%

Differential gene expression in seasonal sympatry: mechanisms involved in diverging life histories

et al. 2016

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In an era of climate change, understanding the genetic and physiological mechanisms underlying flexibility in phenology and life history has gained greater importance. These mechanisms can be elucidated by comparing closely related populations that differ in key behavioural and physiological traits such as migration and timing of reproduction. We compared gene expression in two recently diverged dark-eyed Junco (Junco hyemalis) subspecies that live in seasonal sympatry during winter and early spring, but that differ in behaviour and physiology, despite exposure to identical environmental cues. We identified 547 genes differentially expressed in blood and pectoral muscle. Genes involved in lipid transport and metabolism were highly expressed in migrant juncos, while genes involved in reproductive processes were highly expressed in resident breeders. Seasonal differences in gene expression in closely related populations residing in the same environment provide significant insights into mechanisms underlying variation in phenology and life history, and have potential implications for the role of seasonal timing differences in gene flow and reproductive isolation.

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Seasonal and individual variation in response to GnRH challenge in male dark-eyed juncos (Junco hyemalis)

Cited by 134 publications

References 51 publications

Ignoring the challenge? Male black redstarts ( Phoenicurus ochruros ) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone

Ignoring the challenge? Male black redstarts ( Phoenicurus ochruros ) do not increase testosterone levels during territorial conflicts but they do so in response to gonadotropin-releasing hormone

Up to the challenge? Hormonal and behavioral responses of free-ranging male Cassin's Sparrows, Peucaea cassinii, to conspecific song playback

Differential gene expression in seasonal sympatry: mechanisms involved in diverging life histories

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