ASU Electronic Theses and Dissertations
This collection includes most of the ASU Theses and Dissertations from 2011 to present. ASU Theses and Dissertations are available in downloadable PDF format; however, a small percentage of items are under embargo. Information about the dissertations/theses includes degree information, committee members, an abstract, supporting data or media.
In addition to the electronic theses found in the ASU Digital Repository, ASU Theses and Dissertations can be found in the ASU Library Catalog.
Dissertations and Theses granted by Arizona State University are archived and made available through a joint effort of the ASU Graduate College and the ASU Libraries. For more information or questions about this collection contact or visit the Digital Repository ETD Library Guide or contact the ASU Graduate College at gradformat@asu.edu.
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Description
Biogeography places the geographical distribution of biodiversity in an evolutionary context. Ants (Hymenoptera: Formicidae), being a group of ubiquitous, ecologically dominant, and diverse insects, are useful model systems to understand the evolutionary origins and mechanisms of biogeographical patterns across spatial scales. On a global scale, ants have been used to test hypotheses on the origin and maintenance of the remarkably consistent latitudinal diversity gradient where biodiversity peaks in the equatorial tropics and decreases towards the poles. Additionally, ants have been used to posit and test theories of island biogeography such as the mechanisms of the species-area relationship, being the increase of biodiversity with cumulative land area. However, there are still unanswered questions about ant biogeography such as how specialized life histories contribute to their global biogeographical patterns. Furthermore, there remain island systems in the world’s biodiversity hotspots that harbor much less ant species than predicted by the species-area relationship, which potentially suggests a place ripe for discovery. In this dissertation, I use natural history, taxonomic, geographic, and phylogenetic data to study ant biodiversity and biogeography across spatial scales. First, I study the global biodiversity and biogeography of a specialized set of symbiotic interactions between ant species, here referred to as myrmecosymbioses, with an emphasis on social parasitism where one species exploits the parental care behavior and social colony environment of another species. In addition to characterizing a new myrmecosymbiosis, I use a global biogeographic and phylogenetic dataset to show that ant social parasitism is distributed along an inverse latitudinal diversity gradient where species richness and independent evolutionary origins of social parasitism peak within the northern hemisphere where the least free-living ant diversity exists. Second, I study the unexplored ant fauna of the Vanuatuan archipelago in the South Pacific. Using approximately 10,000 Vanuatuan ant specimens coupled with phylogenomics, I fill in a historical knowledge gap of South Pacific ant biogeography and demonstrate that the Vanuatuan ant fauna is a novel biodiversity hotspot. With these studies, I provide insights into how specialized life histories and unique island biotas shape the global distribution of biodiversity in different ways, especially in the ants.
ContributorsGray, Kyle William (Author) / Rabeling, Christian (Thesis advisor) / Martins, Emilia (Committee member) / Taylor, Jesse (Committee member) / Pratt, Stephen (Committee member) / Wojciechowski, Martin (Committee member) / Arizona State University (Publisher)
Created2023
Description
Throughout the Southwest, complex geology and physiography concomitant with climatic variability contribute to diverse stream hydrogeomorphologies. Many riparian plant species store their seeds in soil seed banks, and germinate in response to moisture pulses, but the climatic controls of this response are poorly understood. To better understand the ecological implications of a changing climate on riparian plant communities, I investigated seed bank responses to seasonal temperature patterns and to stream hydrogeomorphic type. I asked the following questions: Are there distinct suites of warm and cool temperature germinating species associated with Southwestern streams; how do they differ between riparian and terrestrial zones, and between ephemeral and perennial streams? How does alpha diversity of the soil seed bank differ between streams with ephemeral, intermittent, and perennial flow, and between montane and basin streams? Do streams with greater elevational change have higher riparian zone seed bank beta-diversity? Does nestedness or turnover contribute more to within stream beta-diversity?
I collected soil samples from the riparian and terrestrial zones of 21 sites, placing them in growth chambers at one of two temperature regimes, and monitoring emergence of seedlings for 12 weeks. Results showed an approximately equal number of warm and cool specialists in both riparian and terrestrials zones; generalists also were abundant, particularly in the riparian zone. The number of temperature specialists and generalists in the riparian zones did not differ significantly between perennial headwater and ephemeral stream types. In montane streams, alpha diversity of the soil seed bank was highest for ephemeral reaches; in basin streams the intermittent and perennial reaches had higher diversity. Spatial turnover was primarily responsible for within stream beta-diversity—reaches had different species assemblages. The large portion of temperature specialists found in riparian seed banks indicates that even with available moisture riparian zone plant community composition will likely be impacted by changing temperatures. However, the presence of so many temperature generalists in the riparian zones suggests that some component of the seed bank is adapted to variable conditions and might offer resilience in a changing climate. Study results confirm the importance of conserving multiple hydrogeomorphic reach types because they support unique species assemblages.
I collected soil samples from the riparian and terrestrial zones of 21 sites, placing them in growth chambers at one of two temperature regimes, and monitoring emergence of seedlings for 12 weeks. Results showed an approximately equal number of warm and cool specialists in both riparian and terrestrials zones; generalists also were abundant, particularly in the riparian zone. The number of temperature specialists and generalists in the riparian zones did not differ significantly between perennial headwater and ephemeral stream types. In montane streams, alpha diversity of the soil seed bank was highest for ephemeral reaches; in basin streams the intermittent and perennial reaches had higher diversity. Spatial turnover was primarily responsible for within stream beta-diversity—reaches had different species assemblages. The large portion of temperature specialists found in riparian seed banks indicates that even with available moisture riparian zone plant community composition will likely be impacted by changing temperatures. However, the presence of so many temperature generalists in the riparian zones suggests that some component of the seed bank is adapted to variable conditions and might offer resilience in a changing climate. Study results confirm the importance of conserving multiple hydrogeomorphic reach types because they support unique species assemblages.
ContributorsSetaro, Danika (Author) / Stromberg, Juliet (Thesis advisor) / Franklin, Janet (Committee member) / Makings, Elizabeth (Committee member) / Arizona State University (Publisher)
Created2016
Description
Organisms regularly face the challenge of having to accumulate and allocate limited resources toward life-history traits. However, direct quantification of how resources are accumulated and allocated is rare. Carotenoids are among the best systems for investigating resource allocation, because they are diet-derived and multi-functional. Birds have been studied extensively with regard to carotenoid allocation towards life-history traits, but direct quantification of variation in carotenoid distribution on a whole-organism scale has yet to be done. Additionally, while we know that scavenger receptor B1 (SCARB1) is important for carotenoid absorption in birds, little is known about the factors that predict how SCARB1 is expressed in wild populations. For my dissertation, I first reviewed challenges associated with statistically analyzing tissue distributions of nutrients (nutrient profiles) and tested how tissue carotenoid distributions (carotenoid profiles) varied by sex, season, health state, and coloration in two bird species, house finches (Haemorhous mexicanus) and zebra finches (Taeniopygia guttata). Then, I investigated the relationship between dietary carotenoid availability, relative expression of SCARB1, and extent of carotenoid-based coloration in a comparative study of wood-warblers (Parulidae). In my review of studies analyzing nutrient profiles, I found that multivariate analyses were the most common, but studies rarely reported intercorrelations among nutrient types. In house finches, all tissue carotenoid profiles varied by sex, season, and coloration. For example, males during autumn (molt) had higher concentrations of 3-hydroxyechinenone (the major red carotenoid in sexually attractive male feathers) in most but not all tissues compared to other season and sex combinations. However, the relationship between color and carotenoid profiles depended on the color metric. In zebra finches, only muscle and spleen carotenoid profiles varied between immune-challenged and control birds. In wood-warblers, I found that capacity to absorb carotenoids was positively correlated with the evolution of carotenoid-based coloration but negatively associated with liver carotenoid accumulation. Altogether, my dissertation illustrates (a) the context-dependence of tissue carotenoid profile variation, (b) that carotenoid-based integumentary coloration is a reflection of tissue carotenoid profiles, and (c) that digestive physiology (e.g., carotenoid absorption) is an important consideration in the study of diet and coloration in wild birds.
ContributorsWebb, Emily (Author) / McGraw, Kevin J (Thesis advisor) / Deviche, Pierre (Committee member) / Martins, Emilia (Committee member) / Sweazea, Karen (Committee member) / Arizona State University (Publisher)
Created2021
Description
Bouteloua eriopoda (Torr.) Torr., also known as black grama, is a perennial bunchgrass native to arid and semiarid ecosystems in the southwestern region of North America. As a result of anthropogenic climate change, this region is predicted to increase in aridity and experience more frequent extreme drought and extreme wet years. This change in precipitation will no doubt affect black grama; however, few studies have investigated how the specific structural components of this grass will respond. The purpose of this study was to examine the effects of years since start of treatment and annual precipitation amount on tiller and stolon densities, and to test for interaction between the two predictor variables. Additionally, the effects of annual precipitation on ramets and axillary buds were investigated. By using 36 experimental plots that have been receiving drought, irrigated, or control treatments since 2007, tiller density was the most responsive component to both annual precipitation amount and years since start of treatment. Years since start of treatment and annual precipitation amount also had a statistically significant interaction, meaning the effect of precipitation amount on tiller density differs depending on how many years have passed since treatments began. Stolon density was the second-most responsive component; the predictor variables were found to have no statistically significant interaction, meaning their effects on stolon density are independent of one another. Ramet density, ramets per stolon, and axillary bud metabolic activity and density were found to be independent of annual precipitation amount for 2021. The results indicate that multiple-year extreme wet and multiple-year extreme dry conditions in the Southwest will both likely reduce tiller and stolon densities in black grama patches. Prolonged drought conditions reduced tiller and stolon production in black grama because of negative legacies from previous years. Reduced production during prolonged wet conditions could be due to increased competition between adjacent plants.
ContributorsSutter, Bryce Madison (Author) / Sala, Osvaldo E (Thesis advisor) / Makings, Elizabeth (Committee member) / Wojciechowski, Martin F (Committee member) / Arizona State University (Publisher)
Created2022