abstract: Non-native saltcedar (Tamarix spp.) has invaded many riparian communities and is the third most abundant tree in Southwestern riparian areas. I evaluated lizard populations and microhabitat selection during 2009 and 2010 along the Virgin River in Nevada and Arizona to determine the impact of saltcedar. Along the riparian corridor, I observed common side-blotched lizards (Uta stansburiana) within two vegetation types: monotypic non-native saltcedar stands or mixed stands of cottonwood (Populus fremontii), willow (Salix spp.), mesquite (Prosopis spp.) and saltcedar. I predicted that population parameters such as body condition, adult to hatchling ratio, abundance, and persistence would vary among vegetation types. Also, I predicted the presence of saltcedar influences how lizards utilize available habitat. Lizard population parameters were obtained from a mark-recapture study in which I captured 233 individual lizards. I examined habitat selection and habitat availability using visual encounter surveys (VES) for lizards and recorded 11 microhabitat variables where 16 lizards were found. I found no significant difference in population parameters between mixed and non-native saltcedar communities. However, population parameters were negatively correlated with canopy cover. I found that lizards selected habitat with low understory and canopy cover regardless of vegetation type. My results indicate that lizards utilize similar structural characteristics in both mixed and non-native vegetation. Understanding impacts of saltcedar on native fauna is important for managers who are tasked with control and management of this non-native species. / Dissertation/Thesis / M.S. Applied Biological Sciences 2011

Survival is a prerequisite for successful reproduction, and is thus intertwined with fitness. Some physiological systems can improve survival, like the immune system, but compete with other processes for resources. Because animals evolved with resource limitation, it is important to understand how these resource-allocation decisions are made. To meet this end, I performed four investigations addressing how life-history characteristics shift in side-blotched lizards (Uta stansburiana) using laboratory studies and multi-year field sampling. First, I measured metabolic rates in response to different immune challenges and different energy states in male lizards. I found that, surprisingly, cutaneous biopsies were associated with a downregulation of metabolic rate, lipopolysaccharide injection did not affect metabolic rate, and the fastest-healing individuals had the largest decrease in metabolic rate, regardless of feeding treatment. In my second experiment, female lizards were challenged with a cutaneous biopsy and follicle-stimulating hormone to force a trade-off between the reproductive and immune systems. I learned that follicle-stimulating hormone increased metabolic rates and cutaneous biopsies decreased them, and that a combination of both treatments reduced metabolic rate the most. In my third experiment, I sampled wild lizards from northern populations in eastern Oregon and southern populations in southern Utah. In the first year, longer-lived northern lizards had higher circulating corticosterone concentration, decreased reproductive investment, and increased microbiocidal ability, but the subsequent year did not hold to these trends. A subsequent common-garden experiment revealed that southern lizards were faster at healing cutaneous wounds, but lost much more body mass than the northern individuals, which healed more slowly but maintained body mass. Finally, I have conducted a 5-year field investigation addressing the life-history trade-offs associated with urbanization, which reveals interesting effects of precipitation on survival and reproductive effort at urban and rural sites.