Matching Items (10)
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- All Subjects: Urbanization
- Creators: School of Mathematical and Natural Sciences
- Creators: Sweazea, Karen
- Member of: Theses and Dissertations
- Member of: Barrett, The Honors College Thesis/Creative Project Collection
Description
Desert ecosystems are one of the fastest urbanizing areas on the planet. This rapid shift has the potential to alter the abundances and species richness of herbivore and plant communities. Herbivores, for example, are expected to be more abundant in urban desert remnant parks located within cities due to anthropogenic activities that concentrate food resources and reduce native predator populations. Despite this assumption, previous research conducted around Phoenix has shown that top-down herbivory led to equally reduced plant biomass. It is unclear if this insignificant difference in herbivory at rural and urban sites is due to unaltered desert herbivore populations or altered activity levels that counteract abundance differences. Vertebrate herbivore populations were surveyed at four sites inside and four sites outside of the core of Phoenix during fall 2014 and spring 2015 in order to determine whether abundances and richness differ significantly between urban and rural sites. In order to survey species composition and abundance at these sites, 100 Sherman traps and 8 larger wire traps that are designed to attract and capture small vertebrates such as mice, rats, and squirrels, were set at each site for two consecutive trap nights. Results suggest that the commonly assumed effect of urbanization on herbivore abundances does not apply to small rodent herbivore populations in a desert city, as overall small rodent abundances were statistically similar regardless of location. Though a significant difference was not found for species richness, a significant difference between small rodent genera richness at these sites was observed.
ContributorsAlvarez Guevara, Jessica Noemi (Co-author) / Ball, Becky A. (Co-author, Thesis director) / Hall, Sharon J. (Co-author) / Bateman, Heather (Committee member) / School of Sustainability (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
In recent years, ecologists have begun to study the effects of urbanization on species diversity. While urban areas generally suffer decreased biodiversity, some species, termed “urban exploiters”, not only live in the city but depend on urban resources to thrive. It is hypothesized that urban exploiters may succeed in part due to phenotypic plasticity, in which organisms rapidly adjust their physiology or behavior to adapt to novel environmental contexts. In the city, it may be adaptive to display thermal plasticity, as the urban heat island effect caused by concrete and asphalt infrastructure prevents cooling at night. In this study, we observed the decorated cricket Gryllodes sigillatus, an invasive urban exploiter found in metropolitan Phoenix, in two separate experiments. We hypothesized that heat tolerance and activity are both plastic traits in this species. In Experiment 1, we predicted that knock-down time, a measure of heat tolerance, would be negatively affected by acclimation to a laboratory environment. Our results suggest that heat tolerance is affected by recent thermal regimes and that laboratory acclimation decreases knock-down time. In Experiment 2, we predicted that activity would increase with temperature until a point of extreme heat, at which point activity would decline. Statistical analysis for the second experiment reveals that activity decreases at 33°C, a natural urban extreme. This suggests either that 33°C is a thermal limit to physiology or that G. sigillatus is able to alter its behavior to exploit local thermal heterogeneity.
ContributorsVannan, Annika (Author) / Johnson, James Chadwick (Thesis director) / Angilletta, Michael (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Natural Sciences (Contributor) / School of Social and Behavioral Sciences (Contributor)
Created2015-05
Description
Bexarotene is a commercially produced drug commonly known as Targetin presecribed to treat cutaneous T-cell lymphoma (CTCL). Bex mimics the actions of natural 9-cis retinoic acid in the body, which are derived from Vitamin A in the diet and boost the immune system. Bex has been shown to be effective in the treatment of multiple types of cancer, including lung cancer. However, the disadvantages of using Bex include increased instances of hypothyroidism and excessive concentrations of blood triglycerides. If an analog of Bex can be developed which retains high affinity RXR binding similar to the 9-cis retinoic acid while exhibiting less interference for heterodimerization pathways, it would be of great clinical significance in improving the quality of life for patients with CTCL. This thesis will detail the biological profiling of additional novel (Generation Two) analogs, which are currently in submission for publication, as well as that of Generation Three analogs. The results from these studies reveal that specific alterations in the core structure of the Bex "parent" compound structure can have dramatic effects in modifying the biological activity of RXR agonists.
ContributorsYang, Joanna (Author) / Jurutka, Peter (Thesis director) / Wagner, Carl (Committee member) / Hibler, Elizabeth (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05
Description
Bexarotene (Targretin®) is an FDA approved drug used to treat cutaneous T-cell lymphoma (CTCL), as well as off-label treatments for various cancers and neurodegenerative diseases. Previous research has indicated that bexarotene has a specific affinity for retinoid X receptors (RXR), which allows bexarotene to act as a ligand-activated-transcription factor and in return control cell differentiation and proliferation. Bexarotene targets RXR homodimerization to drive transcription of tumor suppressing genes; however, adverse reactions occur simultaneously when bound to other nuclear receptors. In this study, we used novel bexarotene analogs throughout 5 iterations synthesized in the laboratory of Dr. Wagner to test for their potency and ability to bind RXR. The aim of our study is to quantitatively measure RXR homodimerization driven by bexarotene analogs using a yeast two-hybrid system. Our results suggests there to be several compounds with higher protein activity than bexarotene, particularly in generations 3.0 and 5.0. This higher affinity for RXR homodimers may help scientists identify a compound that will minimize adverse effects and toxicity of bexarotene and serve as a better cancer treatment alternative.
ContributorsSeto, David Hua (Author) / Marshall, Pamela (Thesis director) / Wagner, Carl (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Natural Sciences (Contributor) / School of Social and Behavioral Sciences (Contributor)
Created2015-05
Description
The natural habitat as well as the food abundance and food sources of avian species is changing due to urbanization, and such anthropocentric actions could lead to devastating impacts on bird populations. As changes in distribution and nutrition are thought to be related to the gut microbiome, the goal of this study was to determine the relationship between nutritional markers, including body mass, gizzard mass, triglycerides, free glycerol and glycogen, and the gut microbiome in urban and rural house sparrows (Passer domesticus), to understand physiological differences between urban and rural house sparrows. We hypothesized that increased access to human refuse, through urbanization, may significantly alter the gut microbiome and thus, the nutritional physiology-the effects of foods on metabolism-of urban birds. Fecal samples were collected from rural (n=13) and urban (n=7) birds to characterize the gut microbiome and plasma samples were collected to measure nutritional markers using commercially available kits. Following euthanasia, liver samples were collected to measure triglycerides, free glycerol and glycogen. While there were no significant differences in circulating triglycerides or free glycerol between populations, urban birds had significantly greater blood glucose (p=0.046) compared to rural birds, when normalized to body mass. Additionally, rural birds had significantly more plasma uric acid (p=0.016) and liver free glycerol (p=0.044). Higher blood glucose suggests greater accessibility to carbohydrates in an urban setting or higher rates of gluconeogenesis. Uric acid is a byproduct of purine catabolism and a potent antioxidant. Thus, higher uric acid suggests that rural birds may utilize more protein for energy. Finally, higher liver free glycerol in rural birds suggests they metabolize more fat but could also indicate that urban birds have greater glycerol gluconeogenesis, which may consume free glycerol resulting in higher glucose concentrations. However, the current study does not provide evidence for this as there were no significant differences in the gluconeogenic enzyme PEPCK-C levels between urban and rural house sparrows (p= 0.165). While triglyceride, glucose, and uric acid levels differed between urban and rural birds, there were additionally no significant differences in the gut microbiome, indicating that although nutritional physiology can be affected by distribution and varying food availability and sources, differences in the gut microbiome are evident at the phyla level.
ContributorsGadau, Alice (Author) / Sweazea, Karen (Thesis director) / Whisner, Corrie (Committee member) / Crawford, Melisa (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The spread of urbanization leads to habitat fragmentation and deterioration and changes the composition of ecosystems for species all over the world. Different groups of organisms are impacted differently, and insects have experienced loss in diversity and abundance due to changing environmental factors. Here, I collected seed beetles across 12 urban and rural sites in Phoenix, Arizona, to analyze the effects of urbanization and habitat variation on beetle diversity and abundance. I found that urbanization, host tree origin, and environmental factors such as tree diversity and density had no impact on overall beetle diversity and abundance. Beetles were found to have higher density on hosts with a higher density of pods. In assessing individual beetle species, some beetles exhibited higher density in rural sites with native trees, and some were found more commonly on nonnative tree species. The observed differences in beetle density demonstrate the range of effects urbanization and environmental features can have on insect species. By studying ecosystem interactions alongside changing environments, we can better predict the role urbanization and human development can have on different organisms.
ContributorsPaduano, Gabrielle (Author) / Savalli, Udo (Thesis director) / Sweat, Ken (Committee member) / Division of Teacher Preparation (Contributor) / School of Mathematical and Natural Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The ever-increasing importance of cancer and neurodegenerative diseases continues to grow as populations across the world are affected by death and aging. The vitamin A (RXR) and vitamin D (VDR) receptor pathways offer promising potential to aid in treatment of cancer and Alzheimer’s disease. This thesis discusses the potential application of novel analogs of Bexarotene (RXR agonist), MeTC7 (a new potent VDR antagonist), and vitamin D as possible therapeutics for cancer and Alzheimer’s disease.
ContributorsHong, Jennifer (Author) / Jurutka, Peter (Thesis director) / Wagner, Carl (Committee member) / Marshall, Pamela (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Natural Sciences (Contributor)
Created2023-05
Description
With increasing urbanization, organisms face a myriad of novel ecological challenges. While the eco-evolutionary dynamics of urbanization are currently receiving a great deal of attention, the effect of urban disturbance on the microbiome of urban organisms is relatively unstudied. Indeed, studies of the microbiome may illuminate the mechanisms by which some species thrive after urbanization (pest implications), while other species go locally extinct (biodiversity implications). We investigated the gut microbiome of the Western black widow spider (Latrodectus hesperus). L. hesperus is an ideal model system as they are a pest species of medical importance in urban ecosystems, often forming dense urban infestations relative to the sparse populations found in their native Sonoran Desert. To gain insight into the composition of the microbiome in L. hesperus and its potential function, we sampled 4 urban, 4 desert, and 2 laboratory-reared spiders, and high-throughput sequencing of the 16S rRNA V4 region was used to investigate the diversity of gut microbiota. Dominant bacterial phyla across all samples were Firmicutes, Proteobacteria, and Actinobacteria. While desert widows showed more gut microbial diversity than urban widows, the difference was not statistically significant. The relative abundance of taxonomic classes Blastocatellia, Acidobacteriia, and Thermoleophilia detected in desert spiders was especially higher than those in urban and laboratory-reared spiders. However, urban spiders had a higher relative abundance of taxonomic class Actinomycetia. Differences in widow gut microbiome diversity improves our understanding of how features unique to a habitat, like prey diversity and soil microbes, may be shaping their microbiome. Additionally, this work further highlights the impact urbanization has on biodiversity loss, which indirectly develops a new biomarker for differentiating between urban and desert black widow spiders based on their gut microbiome.
ContributorsAsrari, Hasti (Author) / Johnson, Chad (Thesis director) / Sandrin, Todd (Committee member) / Barrett, The Honors College (Contributor) / School of Mathematical and Natural Sciences (Contributor) / School of Life Sciences (Contributor)
Created2022-12
Description
Bioindicators of wildlife health are useful tools for studying the viability of various organisms and populations, and can include a range of phenotypic variables, such as behavior, body size, and physiological parameters, such as circulating hormones and nutrients. Few studies have investigated the utility of total plasma protein as a predictor of environmental or nutritional variation among birds, as well as variation across different seasons and life-history stages. Here I examined relationships between plasma protein and season, urbanization, sex, body condition, molt status, and disease state in house finches (Haemorhous mexicanus). I sampled blood from house finches across three seasons (winter, summer and fall 2021) and measured plasma protein levels using a Bradford assay. I also collected data including condition, sex, and poxvirus infection state at capture, as well as fecal samples to assess gut parasitism (coccidiosis). During the fall season I also estimated molt status, as number of actively growing feathers. I found circulating plasma protein concentration to be lower in the fall during molt than during winter or summer. I also found a significant relationship between circulating protein levels and capture site, as well as novel links to molt state and pox presence, with urban birds, those infected with pox, and those in more intense molt having higher protein levels. My results support the hypotheses that plasma protein concentration can be indicative of a bird’s body molt (which demands considerable protein for feather synthesis) and degree of habitat urbanization, although future work is needed to determine why protein levels were higher in virus-infected birds.
ContributorsDrake, Dean (Author) / McGraw, Kevin (Thesis director) / Sweazea, Karen (Committee member) / Jackson, Daniel (Committee member) / Barrett, The Honors College (Contributor) / School of Life Sciences (Contributor)
Created2022-05
Description
Speciation, or the process by which one population diverges into multiple populations that can no longer interbreed with each other, has brought about the incredible diversity of life. Mechanisms underlying this process can be more visible in the early stages of the speciation process. The mechanisms that restrict gene flow in highly mobile species with no absolute barriers to dispersal, especially marine species, are understudied. Similarly, human impacts are reshaping ecosystems globally, and we are only just beginning to understand the implications of these rapid changes on evolutionary processes. In this dissertation, I investigate patterns of speciation and evolution in two avian clades: a genus of widespread tropical seabirds (boobies, genus Sula), and two congeneric passerine species in an urban environment (cardinals, genus Cardinalis). First, I explore the prevalence of gene flow across land barriers within species and between sympatric species in boobies. I found widespread evidence of gene flow over all land barriers and between 3 species pairs. Next, I compared the effects of urbanization on the spatial distributions of two cardinal species, pyrrhuloxia (Cardinalis sinuatus) and northern cardinals (Cardinalis cardinalis), in Tucson, Arizona. I found that urbanization has different effects on the spatial distributions of two closely related species that share a similar environmental niche, and I identified environmental variables that might be driving this difference. Then I tested for effects of urbanization on color and size traits of these two cardinal species. In both of these species, urbanization has altered traits involved in signaling, heat tolerance, foraging, and maneuverability. Finally, I tested for evidence of selection on the urban populations of both cardinal species and found evidence of both parallel selection and introgression between the species, as well as selection on different genes in each species. The functions of the genes that experienced positive selection suggest that light at night, energetics, and air pollution may have acted as strong selective pressures on these species in the past. Overall, my dissertation emphasizes the role of introgression in the speciation process, identifies environmental stressors faced by wildlife in urban environments, and characterizes their evolutionary responses to those stressors.
ContributorsJackson, Daniel Nelson (Author) / McGraw, Kevin J (Thesis advisor) / Amdam, Gro (Committee member) / Sweazea, Karen (Committee member) / Taylor, Scott (Committee member) / Arizona State University (Publisher)
Created2023