Date of Award

5-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Member

Michael W. Sears, Committee Chair

Committee Member

Saara J. DeWalt

Committee Member

David S. Jachowski

Committee Member

Michael J. Angilletta, Jr.

Abstract

With rapidly warming climates, biologists are challenged to predict organismal responses to environmental variation, changes in biodiversity, and shifts in species distributions. In many cases, organismal responses differ across life stages that exhibit differences in physiological tolerances, habitat requirements, and resource allocations strategies. For instance, mobile life stages can alter behavior in response to changes in the thermal environment, whereas immobile life stages are often vulnerable to warming temperatures due to behavioral constraints and the limited microclimatic conditions experienced over small spatial extents (e.g., an embryo in an egg). Unfavorable developmental conditions can reduce growth, alter developmental rates, and increase mortality. Additionally, the developmental environment can influence subsequent life stages via changes in maturation rates, reproductive success, and survival. Therefore, organismal responses to changing environmental conditions can depend heavily on the physiology of immobile life stages as well as the behavioral and physiology capacities of mobile stages. The first empirical chapter of this thesis (Chapter Two) concerns organismal responses to warming during early ontogeny and the ecological implications of such responses for a widespread ectotherm, the Eastern fence lizard (Sceloporus undulatus). Through a series of field and laboratory experiments, I examined the effects of recurrent sublethal warming on growth, survival, and distribution of S. undulatus. I then incorporated that data into an ecological model that accounts for variation in responses to warming through ontogeny and across geography. Combining empirical studies with mechanistic species distribution modeling, we demonstrated that organisms with thermally sensitive life stages do not have to experience lethal temperatures to undergo negative changes at the individual and population levels. The second empirical chapter (Chapter Three) concerns how the capacity for adaptation to mitigate negative impacts of future climates may vary across species ranges. Using a series of field observations and laboratory-based reciprocal transplant experiment, we examined how geographic variation in maternal behavior and thermal physiology underlies patterns of growth and development across the range of the eastern S. undulatus clade. By demonstrating the extents to which genetic background and environmental conditions affect thermal biology across geography, my data serves to increase understanding of the capacities for populations to persist under climate warming.

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