Digital Commons Network^™

A Genetic Analysis Of The Rare Endemic Astragalus Ripleyi Barneby, Juan Antonio Jaramillo-Chico

Master's Theses

Astragalus ripleyi Barneby is a rare endemic species found in the San Luis Valley of the southern portions of the Rocky Mountains in Colorado and New Mexico. Though not federally listed as endangered, the species is on the Bureau of Land Management’s Sensitive Species List, warranting protection and continued management. This study aims to provide information about the genetic health of the species to inform conservation efforts and provide updated management recommendations. A genetic health analysis was conducted investigating the levels of diversity present in the species, how genetic diversity is structured across the known range of the species and …

A Socio-Ecological Study Of Coyote And Human Interactions In San Francisco Bay Open Space Preserves, Zhiyi Zhou

Master's Theses

Urban open space preserves support both intensive recreation and wildlife, but the information on carnivore activity and visitor perceptions is limited. This study combined camera-trap monitoring and on-site visitor surveys to evaluate activity patterns of medium- to large-bodied mammals and perceptions of coyotes at Windy Hill and Rancho San Antonio Open Space Preserves (South San Francisco Bay Area). From October 2024 to July 2025, thirteen cameras recorded 213,681 photo events; detections were standardized as detections per 1,000 camera-hours. Ten mammal species and two avian species were detected, including four focal carnivores: coyote (Canis latrans), bobcat (Lynx rufus), mountain lion (Puma …

Structure And Diversity Of Play Behavior In Juvenile Belding's Ground Squirrels, Paul O'Driscoll Ii

Master's Theses

Play behavior is ubiquitous among juvenile mammals and can promote motor, social, and cognitive development, providing multiple adaptive benefits to young animals in some cases. The structure of play can be linked to the benefits it confers on individuals. I evaluated the structure of play in juvenile Belding’s ground squirrels (Urocitellus beldingi), a species for which multiple adaptive benefits of play have been identified. I compared juvenile play in U. beldingi to adult sexual and aggressive behavior to determine and classify similarities between juvenile play and adult behavior. I evaluated diversity in the behaviors expressed during play interactions and diversity …

A Methodology To Reconstruct The Extent And Dynamics Of Historic Wildfires (1850-1950) In The Santa Cruz Mountains Of California, David Vásquez Ospina

Master's Theses

This thesis reconstructs the extent and dynamics of historic wildfires in the Santa Cruz Mountains of California between 1850 and 1950 using qualitative archival evidence from historical newspapers, maps, and related documents. A systematically coded database of 225 reports, consolidated into 155 unique wildfire events, was developed to analyze temporal and spatial patterns, ignition sources, vegetation types, suppression strategies, and impacts on communities and infrastructure. Historical rainfall records from the Boulder Creek station were integrated using water-year totals, three-year rolling averages, and standardized precipitation indices to examine how multi-year dryness relates to fire occurrence and size. Linear regressions show only …

Gene Expression Of Anthocyanin Pigments In The California Native Plant Leptosiphon Parviflorus: Interactions Between Flower Color Morphology And Abiotic Stressors, Weston Gonor

Master's Theses

For plants to survive in harsh conditions imposed by abiotic stressors, they must develop mechanisms of adaptation. One of the common types of adaptation seen in plants is the production of anthocyanin pigments, which have been shown to protect plants from UV radiation, metabolic stress, and drought. In this study, we used the flower color polymorphic species Leptosiphon parviflorus to investigate the role of anthocyanin pigments in protecting plants from abiotic stress. To accomplish this, RNA samples were taken from flower, leaf and root tissue of different flower color morphs of Leptosiphon parviflorus (Polemoniaceae) grown in high magnesium and water …

Forgotten Landscapes: Using Original Land Surveys To Understand The Historic Distribution Of Cane Brakes In Wayne County, Ms, Chad Mackness

Master's Theses

This study investigates the historical presence and ecological significance of Arundinaria gigantea (giant cane) in 1810, Wayne County, Mississippi, using original survey documents. These records provide rare quantitative insights into the distribution of cane brakes, revealing that A. gigantea possibly represented up to 44% of the surveyed landscape, likely second only to Pinus palustris (longleaf pine).

This research involved digitizing historical surveyors' notes, transcribing them into a structured format, and extracting spatial data for GIS analysis. The methodology developed for this research can be used to ensure the preservation and usability of these historical documents for future research. …

Anthropogenic Litter In Freshwater Ecosystems: Effect On Ecosystem Processes And Spatial Distribution, Emily Johnson

Master's Theses

The rapid increase of plastic production and disposal into the environment has resulted in anthropogenic litter (i.e., trash; AL) becoming a global problem. In aquatic ecosystems, macro- and microplastics are long-lived, mobile, and interact with the physical and chemical components of aquatic ecosystems. Our objectives were to: (1) assess the impact of microplastic pollution on the ecosystem processes of ecosystem metabolism and N2 flux in an oligotrophic lake and (2) to assess the abundance and assemblage of anthropogenic litter in a large urban river. For objective (1), we added microplastics at a range of concentrations to littoral mesocosms. Ecosystem metabolism …

When Trees Disappear: Understory Successional Implications Of Sudden Oak Death And High-Severity Wildfire In Big Sur, California, Sam J. Balthazard

Master's Theses

The rapidly emerging disease sudden oak death, caused by the non-native pathogen Phytophthora ramorum, is transforming coastal California forests by driving extensive mortality of tanoak (Notholithocarpus densiflorus) and increasing fire severity. As a novel disturbance, sudden oak death and its interaction with wildfire may catalyze unexpected shifts in successional trajectories and reconfigure forest understory communities. Furthermore, how tanoak influences the forest understory and how its decline might reshape understory dynamics remain poorly understood. We hypothesize that disease alone and the compounding disturbances of disease and wildfire alter successional dynamics, and that the potential functional extinction of N. …

Comparing The Effectiveness Of Low Impact Image Analysis To Traditional Vegetation Sampling In A Branford Marsh, Peter T. Porrello

Master's Theses

The growing need for non-intrusive research methods has led to a surge in passive data collection, such as audio recorders, data loggers, and camera traps, in the ecological field. This improves the capacity to observe fragile habitats without causing any harm and gives researchers new perspectives on the natural world. A non-invasive cable camera system is suggested as a means of gathering data to lessen these ecological disruptions. By taking images of the salt marsh's surface, this technique will minimize plant destruction and lower CO2 emissions brought on by foot traffic through the marsh, whilst producing data that is on …

Pollinator Plant Communities Within Restored Montane Longleaf Pine Ecosystems, Hanen Van Rossem

Master's Theses

Historically the fire-dependent and biodiverse longleaf pine (Pinus palustris) ecosystem was the dominant ecosystem of the Southeastern US. This ecosystem’s range was massively reduced due to land conversion and fire exclusion, causing the decline of many native species. Efforts to restore and protect longleaf pine stands are now ongoing with the goal of expanding habitat and refuge for threatened species. Differences in restoration practices and prior land use may influence the extent to which restored habitat patches can support pollinators and their plants. This study compared pollinator plant biodiversity between restored neighboring montane longleaf pine stands that differed in …

Behavioral Ecology And Physiology Of Spotted Turtles (Clemmys Guttata) In A Fragmented And Polluted Landscape, Jessica Rojas Lindberg

Master's Theses

Turtles are one of the most threatened groups of animals across the globe. This is especially true for freshwater turtles that rely on multiple habitats to fulfill their life history requirements. Wetlands are a crucial habitat type for many freshwater turtle species, and this ecosystem has been susceptible to conversion, fragmentation, and pollution. In turn, these hazards to wetland habitats threaten already declining freshwater turtle populations. The spotted turtle (Clemmys guttata) is a species of freshwater turtle that is particularly at-risk due to life history traits as well as habitat fragmentation and pollution. This study aims to investigate the effects …

No Change In Functional Ecology Or Body Size In Response To A Global Climate Event In The Late Maastrichtian Owl Creek Formation, William T. Rizza

Master's Theses

During the last 300 ka of the Maastrichtian, global temperatures increased and decreased by ~2℃, likely caused by a pulse of Deccan volcanism. The Owl Creek Type Section in Mississippi records some portion of the last 400 ka of the Late Maastrichtian. It is expected that marine invertebrates will demonstrate a taxonomic, ecological, or morphological response to rapid temperature change. I anticipate a decrease in taxonomic diversity and shell volume and an increased abundance of low activity-level species, similar to the ecological impacts observed in response to Large Igneous Province eruptions in the geologic record. Clumped isotope paleotemperature reconstruction recovers …

Seasonal Dynamics Of The Introduced Sponge Hymeniacidon Perlevis In The Elkhorn Slough, California, Usa, Jackson Hoeke

Master's Theses

Hymeniacidon perlevis is a cosmopolitan sponge with a seasonal life cycle We investigated seasonal and interannual dynamics of H. perlevis in Elkhorn Slough estuary, where it is an introduced species, and explored correlations between sponge cover and environmental conditions. We used sponge cover to estimate the potential effects H. perlevis on its environment and how those could vary across its seasonal life cycle. We found that successful recruitment is currently restricted to the upper estuary and while it varies annually, the frequency and density of sponge recruits have generally increased from 2007 to 2023. A seasonal life cycle was confirmed …

Descriptive Study Of Adult Male Acheta Domesticus Phonotaxis, Dana Husana

Master's Theses

The phonotactic behavior of male Acheta domesticus has not been described at length. The present study evaluates the phonotactic responses of male A. domesticus in relation to age. Male crickets of different ages (young and old) were exposed to calls with attractive and non-attractive syllable periods for this species. Both age groups exhibited phonotaxis but did not show a preference towards the attractive call over the non-attractive ones. No significant relationship was found between age and phonotactic response. Additionally, no significant differences were observed between age and preferred syllable period. Acoustic responses were also observed in some of the older …

Factors Affecting California Grassland Biodiversity: Two Case Studies, Nora Bales

Master's Theses

Biodiversity loss over the last century has been significant and is projected to increase. Biodiversity loss is accelerating due to climate change and habitat loss and degradation. Biodiversity supports key ecosystem services including pollination services, climate regulation, and water filtration. Biodiversity conservation is a top priority for land managers and researchers, however many ecological studies with practical applications lack a thorough understanding of the soil environment in their study system. We conducted two case studies integrating soil and plant data to answer management questions. The first case study investigated the relationship between a threatened plant, Hooveria purpurea var. purpurea and …

Benthic Habitat Mapping Of Mountain Top Bank Within The Northern Gulf Of Mexico Through Integrated Geophysical And Visual Data Analysis, Bethany Pertain

Master's Theses

Mesophotic coral ecosystems (MCEs) are among the seafloor ecosystems that have been poorly studied throughout the world’s oceans, but they are a vital and diverse ecosystem that should be prioritized for future mapping and ecological studies. Priority should be given to them because they possess natural, social, and economic values, and face a variety of threats, all of which, if not better understood will result in the loss of this unique ecosystem. Insights into these ecosystems, among other deep-sea environments, are lacking due to difficulty accessing them, inherent lag between data collection by an autonomous system and observation by a …

Lichens Of Ultramafic Rocks: A Multidisciplinary Approach To Understanding The Ecology Of An Understudied Organism In A Well-Studied System, Michael Mulroy

Master's Theses

Lichens are among the most prominent and successful life forms of metal-rich habitats, including ultramafic rocks and soils; however, research on lichens of ultramafic habitats is limited, especially on the North American continent. A review of the published literature on lichens of ultramafic substrates in North America yielded a total of 437 lichen species reported from ultramafic rocks and soils. Lichen assemblages of ultramafic substrates vary in composition and are dominated by acidophytic (low pH preferring) taxa with a minor, but consistent, basiphytic (high pH preferring) component. Species lists from ultramafic habitats in different geographic regions varied widely, suggesting that …

Habitat Value Of Stormwater Retention Basins For Avian Species In The South San Francisco Bay, Maya D. Briones

Master's Theses

Shorebird populations are declining worldwide due to habitat fragmentation, degradation, and loss. A potential, understudied set of resources that might be used to benefit waterfowl, especially breeding shorebirds, are artificial wetlands such as stormwater retention basins. This study evaluated the habitat value of stormwater retention basins in the San Francisco Bay Area by measuring species abundance, richness, and behavior. Seston, or biota and other suspended material, was collected and tested for mercury contents. Additionally, the habitat features within each basin were recorded and tracked for changes over a year. The stormwater retention basins supported a higher diversity of bird species …

Tree Removal From An Encroached Coastal Grassland Restores Soil Bacterial Communities Before Fungal Communities, Ka Ki Law

Master's Theses

Woody species encroachment depletes historic grassland biodiversity and degrades ecosystem function around the world. In particular, the encroaching trees can shift soil properties and microbial communities, which play critical roles in plant health and global nutrient cycling. Little is known about how removing encroached trees affects soil ecosystems, however. Over the last century, Pinus radiata and Hesperocyparis macrocarpa (non-native to the area) both encroached into coastal prairies at Rancho Corral de Tierra in California, and selected trees were removed in 2017 and 2018 to restore grassland habitats. To examine the impacts of encroachment and removal on the soil ecosystem, I …

Trophic Ecology And Mercury Concentrations Of Canary Rockfish (Sebastes Pinniger) In The California Current System, Michaela M. Melanson

Master's Theses

Canary rockfish are a profitable fishery resource that has failed and successfully recovered in the 21st century. This study aimed to evaluate their trophic ecology through stomach content and stable isotope analysis and relate these to their mercury concentrations, biological traits, and environmental conditions. Canary rockfish consume mostly krill and teleosts with their geographic location affecting the proportion of prey items, suggesting regional environmental effects: chlorophyll-a, relief, port, and depth impact dietary choices. Mean ??13C values (-17.18 ± 0.54) significantly increased in individuals residing in deeper depths, higher latitudes, higher productivity, and higher temperatures, and in sexually mature individuals. Mean …

Ectotherm Thermoregulation At Fine Scales: Novel Methods Reveal A Link Between The Spatial Distribution Of Temperature And Habitat Quality, Ian Axsom

Master's Theses

Investigating ecological questions at the scale of individual organisms is necessary to understand and predict the biological consequences of environmental conditions. For small organisms this can be challenging because we need tools with the appropriate accuracy and resolution to record and quantify their ecological interactions. Unfortunately, many of our existing tools are only appropriate for medium to large organisms or those that are wide ranging, inhibiting our ability to investigate the ecology of small organisms at fine scales.

In Chapter 1, I tested a novel workflow for recording animal movements at very fine spatial and temporal scales. The workflow combined …

Population Genetics Of Cownose Rays, Rhinoptera Spp. In The Western Atlantic, Helen Weber

Master's Theses

Using molecular tools (e.g., the NADH subunit II mitochondrial gene), this study was the first to document the Brazilian cownose ray, Rhinoptera brasiliensis, within the northwestern Atlantic (NWA), and was the first study to examine population structure in R. brasiliensis within the NWA or northern Gulf of Mexico (GMX), revealing novel insights into the population biology of the animal and extending its range by nearly 1,500 km. This study also examined the sympatrically occurring American cownose ray, R. bonasus, and found population structure between the NWA and the GMX and the NWA and the southwestern Atlantic (SWA). High …

The Shallow Benthic Invertebrate Recovery From The End-Cretaceous Mass Extinction Across The Gulf Coastal Plain, Ronan B. Beltracchi

Master's Theses

The Gulf Coastal Plain, in the southeastern United States, contains several sites with well-preserved fossil assemblages from the Cretaceous- Paleogene boundary (K/Pg). Changes in benthic macroinvertebrate assemblages after mass extinction events commonly include reduction in body size of surviving organisms and preferential survival based on ecospace occupation. This study examines patterns of functional ecology and body size change in mollusk fossils from bulk samples collected throughout the post-extinction recovery interval at a well-studied boundary site from Darting Minnow Creek in Brazos, Texas USA and a recently described K/Pg boundary section on the Ouachita River in Malvern, Arkansas USA. The proportional …

The Modern-Day Effect Of Holc Redlining On Neighborhood Development, Liubov Ivashov

Master's Theses

Racial segregation, which happened more than one hundred years ago in the U.S., is a fundamental cause of economic inequality for people living in historically segregated neighborhoods today. Redlining was one form of federal policy that forced to separate communities by race even more after the Great Depression. The Home Owners Loan Corporation (HOLC) maps are widely used in economic research papers as one of the most comprehensive sources of data available to measure the effect of residential segregation. In this paper, using the Historical Redline Score (HRS) method, the author measured the association between modern-day population distribution, rent prices, …

Research Handling Effects On Stress Hormones, Blood Parameters, And Heart Rate In Juvenile Northern Elephant Seals (Mirounga Angustirostris), Lauren A. Cooley

Master's Theses

Wildlife researchers must balance the need to safely capture and handle their study animals to sample tissues, collect morphological measurements, and attach dataloggers while simultaneously ensuring their results are not confounded by stress artifacts caused by handling. To determine the physiological effects of research activities including chemical immobilization, transport, instrumentation with biologgers, and overnight holding on a model marine mammal species, I collected hormone, blood chemistry, hematology, and heart rate data from 19 juvenile northern elephant seals (Mirounga angustirostris) throughout a translocation experiment. Across my six sampling timepoints, cortisol and aldosterone data revealed a moderate hormonal stress response to handling …

Examining The Ecological And Social Implications Of Parklets And Plazas Across Multiple Urban Scales, Joshua L. Muller

Master's Theses

Faced with population increases but stagnant capital improvements and impacts from global warming, cities around the world are experimenting with smaller-scale and cheaper strategies in order to accommodate the new influx of residents. New York City has led the way in converting low-efficiency intersection space into public plazas with a limited range of permanently installed elements and San Francisco has pioneered the concept of the parklet, which converts two to four street parking spaces into a modular and flexible pedestrian space. I seek to answer two questions about these spaces: What are common factors influencing the viability and successful implementation …

Wicked Problems: Understanding How Cities And Counties In California Are Tackling Climate Change And Homelessness, Guadalupe Michelle Franco

Master's Theses

California continues to endure the detrimental effects of climate change, such as poor air quality, flooding, and heatwaves. Concurrently, the state has seen an increase in the number of unhoused communities due to various ramifications such as rapid urbanization, failed political leadership, and restricted housing policies. While unhoused communities fight to access basic services, they must also now adapt to the looming impacts of climate change. Unhoused populations are especially vulnerable to climate change as they have limited access to shelter, spend the majority of their time outdoors, and lack the economic ability to adapt. While cities and counties are …

Resistance To Rattlesnake Venoms In An Eastern Colorado Rodent Community, Neil Balchan

Master's Theses

The grasslands of eastern Colorado are inhabited by two species of rattlesnakes, the Prairie Rattlesnake (Crotalus viridis) and the Desert Massasauga Rattlesnake (Sistrurus tergeminus edwardsii). An array of rodent species, both native and introduced, also occupy these grasslands, and serve as a varied prey base for the previously listed rattlesnakes. Predator-prey interactions in this system gain an additional level of complexity due to the presence of venoms, a chemical arsenal possessed by both rattlesnakes to incapacitate their prey. Rodents in other systems have demonstrated resistance to snake venoms, and there is potential for a similar dynamic to be present in …

A Floristic Study Of The Cal Poly Swanton Pacific Ranch And A New Combination In Sanicula Crassicaulis (Apiaceae), Sanicula Crassicaulis Var. Nudicaulis, Reed J. Kenny

Master's Theses

Globally we are experiencing a biodiversity crisis and potentially a sixth mass extinction event. Plant specimens are one of the best, most concrete records of biodiversity that we can create. Despite this, the rate of plant collecting has declined steeply since World War II. Now more than ever, plant collections are vital, both for the purpose of quantifying the plant biodiversity in an area and for discovering previously unrecognized diversity.

In Chapter 1, we conducted a floristic survey of the Cal Poly Swanton Pacific Ranch. The Swanton Pacific Ranch (SPR) is located north of the small town of Davenport California, …

Development And Employment Of Environmental Dna Methods For The Detection Of Bull Sharks (Carcharhinus Leucas) In A Freshwater And Estuarine Interface In The Mobile-Tensaw Delta And Mobile Bay, Alabama, Katherine Schweiss

Master's Theses

Species conservation and management is influenced by the quality of monitoring methods employed, especially when targeting elusive, but ecologically significant species, like elasmobranchs. Bull Sharks (Carcharhinus leucas) are highly mobile predators that rely on estuaries and freshwater rivers for maturation, resources, and refuge; their ability to withstand changing environmental conditions may mean they are linking ecosystems through their habitat usage and movements. Rather than setting nets or attaching acoustic monitoring devices, which can be expensive, time-consuming, and invasive, the analysis of environmental DNA (eDNA) for tracing species presence was used to target C. leucasDNA. The present research …