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Functional Consequences of Acute Temperature Stress in the Western Fence Lizard, Sceloporus Occidentalis

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dc.contributor.advisorDuncan J. Irschick
dc.contributor.advisorStephen D. McCormick
dc.contributor.advisorBernard B. Rees
dc.contributor.authorMcMillan, David Michael
dc.contributor.departmentUniversity of Massachusetts Amherst
dc.date2023-09-22T20:57:51.000
dc.date.accessioned2024-04-26T19:46:11Z
dc.date.available2024-04-26T19:46:11Z
dc.date.issued2010-02-01
dc.description.abstractUnderstanding the effects of natural variation in environmental temperature on organisms and how those organisms evolve to live in different thermal environments is a central tenet of evolutionary physiology. Phenotypic differences among populations are the result of local adaptation, innate genetic differences between populations, and phenotypic plasticity, differential responses to the environment. Although not mutually exclusive, distinguishing between these paradigms can help illuminate species boundaries resulting from thermal limitations in physiology. For my dissertation, I examined geographic variation in measures of thermal physiology of the western fence lizard, Sceloporus occidentalis to understand the relative role of adaptation and acclimation in determining the thermal biology of populations of this species living in different thermal environments. To achieve this goal I measured three indices of physiological function; body temperature, thermal tolerance and heat shock protein (Hsp70) abundance, across geographic and seasonal variation in temperature. Furthermore, I examined variation in sprint speed performance before and after heat stress and its relationship to Hsp70 to determine if stress protein expression is a reliable indicator of whole organism physiological stress. I found that geographic location can have a major effect on thermal physiology and performance in S. occidentalis in that thermal tolerance, Hsp70, and sprint speed varied with site and season with warmer southern sites typically more heat adapted than cooler northern sites. I also found a trade off in thermal tolerance suggesting that specialization to temperature was occurring in these lizards. Finally, lizards with increased Hsp70 were typically slower after heat stress indicating that Hsp70 is a reliable indicator of organism stress. Despite these findings, there was no difference in body temperature among sites and seasonal patterns in thermal tolerance suggest that during certain times of the year plastic responses to temperature may mask adaptive differences. Here, I argue that temperature differences between sites has resulted in temperature adaptation at these sites, but that plastic responses to seasonal variation in temperature can become more important during certain times of the year. Although these relationships have been thoroughly studied in invertebrate organisms, further research should examine whether these patterns exist in other vertebrate ectotherm species.
dc.description.degreeDoctor of Philosophy (PhD)
dc.description.departmentOrganismic and Evolutionary Biology
dc.identifier.doihttps://doi.org/10.7275/1263371
dc.identifier.urihttps://hdl.handle.net/20.500.14394/38595
dc.relation.urlhttps://scholarworks.umass.edu/cgi/viewcontent.cgi?article=1153&context=open_access_dissertations&unstamped=1
dc.source.statuspublished
dc.subjectHeat shock proteins
dc.subjectLizards
dc.subjectSceloporus occidentalis
dc.subjectSprinting speed
dc.subjectThermal tolerance
dc.subjectEcology and Evolutionary Biology
dc.titleFunctional Consequences of Acute Temperature Stress in the Western Fence Lizard, Sceloporus Occidentalis
dc.typedissertation
dc.typearticle
dc.typedissertation
digcom.contributor.authorisAuthorOfPublication|email:dmcmill@gmail.com|institution:University of Massachusetts Amherst|McMillan, David Michael
digcom.identifieropen_access_dissertations/156
digcom.identifier.contextkey1263371
digcom.identifier.submissionpathopen_access_dissertations/156
dspace.entity.typePublication
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