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- Creator:
- Lona, Irene
- Description:
- Walnut (Juglans) and wingnut (Pterocarya) trees have been declining in response to Thousand Cankers Disease (TCD). The TCD pathogen, Geosmithia morbida, is vectored by a phloeophagous bark beetle, the walnut twig beetle (Pityophthorus juglandis Blackman). To understand P. juglandis host selection, the following were investigated at two orchards in Northern California: 1) The susceptibility of two walnut species (Juglans californica and J . major) native to the western USA by comparing P. juglandis flight and landing responses to unbaited branch sections and 2) The relationship between English walnut (Juglans regia) tree health, represented by several levels of plant water stress, and P. juglandis colonization success. P. juglandis preferred to land on J. californica over J. major. With J. regia, there was no significant difference in P. juglandis activity between branches from trees in high water stress and low water stress groups (both baited with P. juglandis aggregation pheromone). No P. juglandis colonization activity was observed in unbaited branches from the negative control group (unbaited). Activity by P. juglandis was found primarily on 4 cm diameter branches. Other invasive bark and ambrosia beetles such as Hypothenemus eruditus and Xyleborinus saxeseni; and an invasive longhorned beetle, Nathrius brevipennis preferred to land on J. major over J. californica. Collections of H. eruditus and an invasive ambrosia beetle, Xyleborus affinis, in Butte County reflect the northernmost records of these species in California. No significant relationships were found in J. regia between water stress and activity by N. brevipennis and a parasitoid Gildoria sp; however, activity by N. brevipennis and Gildoria sp. was found primarily on secondary 1 cm diameter branches (twigs). In conjunction with this study, significant flight responses of N. brevipennis and X. saxeseni to ethanol were recorded in a J. regia orchard. Overall, this study demonstrated that volatile cues from Juglans may influence host selection by P. juglandis and associated insects.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Cochran, Holly Jean
- Description:
- My study aimed to quantify nesting habitat availability for cavity-nesting birds in restored and remnant patches of riparian forest on the Sacramento River. I explored three hypotheses: 1) that older restored forests will attract more cavity-nesting birds in comparison to younger restored forests because more mature habitat features are available; 2) that the vegetation structure between remnant forests, younger restored forests, and older restored forests are distinct, owing to temporal developmental processes that differ in each subset of forest; and, 3) that the vegetation structure within each forest type affects the presence of secondary cavity- nesting birds and primary cavity-nesting birds differently because of their distinct nesting requirements. I performed vegetation surveys, cavity surveys, and bird point-count surveys to describe habitat structure and estimate bird density, cavity availability, and suitable cavity- building substrate (potential nesting substrate) in the form of snags and broken tree limbs. Surveys were conducted in each of six different aged riparian forests (remnant and 13- to 21- year old restored) in Glenn and Tehama Counties in Northern California. In restored forests, I determined that restoration sites between the ages of 13- and 21- years old (time since initial planting) do not have significantly different habitat availability for cavity-nesting birds. Features included in this analysis were potential nesting substrate and cavity density (p=0.176 and p=0.121 respectively). When comparing remnant forests with restored forests, the potential nesting substrate and cavity density were significantly different (p=0.005 and 0.003, respectively). A multivariate analysis of the vegetation structure comparing restoration forests and remnant forests showed there are trends in vegetation features that can differentiate remnant forests and 13-year old restored forests. Through a mixed model linear regression, I determined that primary cavity nesters were more sensitive to specific habitat features than secondary cavity nesters. Tree density, snag density, and forest age were important for both groups, but secondary cavity nesters were also sensitive to the number of different tree species present and the amount of potential nesting substrate available. It may be inferred that secondary cavity nesters are more likely to be observed in remnant forests, since these forests have a wider variety of tree species and far more potential nesting substrate available than restored forests.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Bianchini, Elizabeth A.
- Description:
- Recent human infections with avian influenza viruses (AIV) highlight the need for continued surveillance of AIV in waterfowl. California’s Sacramento Valley is an important wintering site for waterfowl from which avian influenza viruses may be isolated. To determine host correlates of AIV infection and better understand the risk posed by AIV circulating in California, we collected cloacal swabs from 2,066 hunter-killed ducks across four hunting seasons at different locations in the Sacramento Valley. We determined that Northern shovelers have a higher AIV infection rate than other waterfowl species from which we commonly sampled and that the relationship between sex and AIV infection is a poorly understood factor that needs to be investigated on a species level. Additionally, we detected three viruses of the subtype H7N3. Whole genome sequencing of these viruses revealed genetic markers that have been correlated with increased pathogenesis in mammals. All three H7N3 viruses were capable of replication in mammalian cells at levels similar to a human seasonal H1N1 virus. Additionally, at least one of these H7N3 viruses is able to cause disease in mice similarly to a human seasonal H1N1 virus. These results provide insights into host factors of AIV susceptibility that can help guide future surveillance efforts as well as evidence of novel subtype H7N3 with mammalian adaptations that could pose a risk to public health and therefore should be monitored closely.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Stompe, Dylan K.
- Description:
- This study examined the diets of two predatory fish species, the native Sacramento Pikeminnow (Ptychocheilus grandis) and the introduced Striped Bass (Morone saxitilis), within the Sacramento River, CA, USA. Sampling occurred between March and December 2017 and was comprised of two primary components. The northern survey component was done via hook and line sampling, on a 35 kilometer reach near Chico, CA, and the southern survey component was done via seven fyke traps located near Sacramento, CA. Stomach contents were collected via non-lethal gastric lavage and were later processed using visual, gravimetric, and genetic techniques. Relative abundance of Sacramento Pikeminnow was significantly higher at man-made structure sites and Striped Bass relative abundance was positively correlated with water temperature. Diets of Sacramento Pikeminnow and Striped Bass captured near Chico, CA were not different, and Striped Bass captured near Chico, CA had significantly different diets to those captured near Sacramento, CA as determined by PERMANOVA analysis.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Rich, Shannon
- Description:
- Flammulated owls (Psiloscops flammeolus) are small nocturnal owls that are thought to migrate long distances every year from summer breeding grounds in the western United States and southern Canada to winter habitat in Mexico. They are cryptic and elusive cavity nesters and little is known about their migratory patterns or winter habitat. They have been named a Species of Concern by the U.S Fish and Wildlife Service be cause of potential habitat destruction. The goal of this research was to track the movements of these owls during their migratory season and over the winter using light-level geolocators, which records ambient light levels that correspond to sunrise and sunset times to determine specific bird locations. During 2012-2013, 60 geolocators were attached to male and female flammulated owls in breeding sites in Washington, Colorado, Utah, and California. In 2013-2014, 16 of these geolocators were recovered from birds in California, Utah, and Colorado. The migratory routes of these birds were analyzed using GIS and further analysis was performed to determine habitat characteristics of their winter home ranges in Mexico. Consistencies in migratory routes and wintering areas between owls from different breeding locations contributed to greater knowledge about the migratory ecology of this owl. Novel results for the migratory behavior of a mated pair from California who used comparable routes and wintering areas before returning to breed together the following year, as well as a female owl from Utah with multiple years of data that showed her using a very similar route and wintering area between years also provided new information that was not yet confirmed about female flammulated owls. This geolocator analysis along with additional research on habitat preferences of flammulated owls in California is the first step in assessing the current status of this species with the goal of a broader western U.S. effort in the future.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Pukini, W. Cory
- Description:
- Kelp forest ecosystems are sensitive to changing global environmental conditions and unsustainable fishing practices (Tegner and Dayton 2000). Natural resource managers have implemented marine protected areas (MPAs) to mitigate ecosystem collapse and conserve fisheries stocks around the globe (Castilla and Moreno 1982). In California, MPAs have been primarily established as a way to mitigate unsustainable fishing practices of the past, while insuring a future for marine resources (Airamé et al. 2003). The establishment and implementation of MPAs has proven an effective conservation tool, but further research is needed to better understand the habitat selection process (Young et al. 2010). This study examined nearshore benthic habitat associations between select species in kelp forest ecosystems of the northern Channel Islands within the Channel Islands National Park, with the intended purpose of identifying specific habitat characteristics for a suite of selected species. Important habitat associations help inform continued and adaptive management efforts and guide the establishment of new MPAs in kelp forest ecosystems. Mapping efforts to help characterize habitat were focused on long-term biological monitoring sites that are part of the Channel Islands National Park Kelp Forest Management (KFM) program (Kushner et al. 2018). Side scan and multibeam sonar technologies were used to map previously uncharted areas of the rocky reef and seafloor of nearshore environments of Anacapa and Santa Cruz Islands at a fine scale resolution of 10-15 cm and data was summarized to characterize habitat at the two-meter^2 and 10m^2 (two and ten-meter) scales. Physical habitat parameters of interest included bathymetry (average depth from sea surface), rugosity (a ratio that measures the topographic complexity of the seafloor), and slope (gradient or steepness of elevation change within a defined area). Eleven sites were sampled for physical variables and species encounters recorded between 2005 and 2013 provided the data to analyze associations between the physical setting and habitat use. Five of the eleven sampled areas in my study were found within MPAs including State Marine Reserves (SMRs) and State Marine Conservation Areas (SMCAs). Six of the eleven sites were located on Santa Cruz Island and five were on Anacapa Island. Selection of target species was derived from a preexisting list of monitored kelp forest inhabitants. Target species were selected with the help of Channel Islands National Park KFM biologists to represent the broadest spectrum of benthic microhabitat users in the kelp forest community. The eight species selected for my study at the two-meter scale have well documented ecological roles within the Channel Island National Park. Two of these species, giant kelp and giant spined sea star, were also observed and analyzed at a larger ten-meter scale. A backwards eliminating stepwise regression (BESR) model for habitat characterization between seafloor statistics (bathymetry, rugosity, and slope) and select kelp forest species was implemented to identify habitat associ ations. In addition, protection status and island were included in the analysis. Results showed that species indicative of healthy kelp forest ecosystems were found in greater numbers inside the MPA boundaries, while the inverse was true for species that represent disturbed systems. In addition, the ten-meter sampling scale was found to be a more accurate predictor of species encounters for the two target species. My study also identified fine scale habitat preference varied among several target species (i.e., purple sea urchin encounters were highly dependent on bathymetry). The results of this research are important to natural resource managers and are intended to help inform decision makers responsible for kelp forest ecosystems and the establishment and implementation of MPAs.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Hanson, Tina
- Description:
- 95% of the cases of chronic myeloid leukemia (CML) are caused by a chromosomal translocation linking the breakpoint cluster region (BCR) gene to the Abelson murine leukemia viral oncogene-1 (ABL1). Downstream of BCR-ABL is growth receptor bound protein-2 (GRB2), which binds to BCR-ABL via its src-homology-2 (SH2) domain. This binding constitutively activates growth pathways while down regulating apoptosis leading to an over proliferation of immature and dysfunctional myeloid cells. Four novel SH2 antagonists were developed with three of the four showing a significant reduction in proliferation of a BCR-ABL+ leukemia cell line. To elucidate the mechanism of action, an enzyme-linked immunosorbent assay (ELISA), a surface plasmon resonance (SPR) assay, and a cellulose nitrate (CN) filter assay were performed. These assays indicated that one of the three effective molecules, NHD2-15, antagonized the SH2 domain of GRB2 with a Kd value of 119 ± 2 μM, bringing us closer to developing a new treatment for CML.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Belmonte, Rebecca
- Description:
- Zebrafish (Danio rerio) is an excellent model organism for studying embryonic vertebrate development due to their conserved genome with humans, external development, and ease of observation under the microscope. The gene SON is found on the twenty-first chromosome of humans and is often overexpressed in patients with leukemias, particularly acute megakaryoblastic leukemia. Previously, we showed that mutations in the mRNA splicing co-factor gene SON cause malformations in human and zebrafish spines and brains. We performed these studies by knocking down the expression of the zebrafish homolog of SON in zebrafish at the single-cell developmental stage with specific morpholinos (MOs). In addition to the brain and spinal malformations we also observed abnormal blood cell levels with son knockdown. We then investigated how blood production was altered when levels of son were lowered. Decreased levels of SON resulted in impaired blood flow and lower amounts of red blood cells when visualized with hbaa:GFP transgenic fish. There was also a reduction in thrombocytes seen with cd41:GFP fish and verified with flow cytometry, and myeloid cells, as seen with mpx:GFP fish. We also saw a significant decrease in the quantity of T cells, visualized with lck:GFP fish. However, when we plated the hematopoietic stem and progenitor cells (HSPCs) from zebrafish with reduced levels of son, we saw no difference in colony forming capability. Further investigation of son and its effect on blood development should establish how misexpression of this gene negatively impacts human health.
- Resource Type:
- Graduate project
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Schleiger, Rachel
- Description:
- Meadows in the Sierra Nevada are characterized as wet, heterogeneous habitats with diverse plant communities, often being biodiversity hot spots. These meadows not only provide resources for wildlife but also filter and store snowmelt, providing sustained water sources for both wildlife and Californians. Recognition of meadow significance combined with persistent human disturbance motivates restoration efforts to improve hydrologic connections and biotic health within these meadows. This research is evaluating the trajectory of a restored montane meadow in Sierra Nevada, California. Comparing soil moisture, plant community composition, and exotic species extent of this restored meadow to disturbed and less disturbed meadows provided context for this assessment. Results indicated soil moisture was highest in the restored meadow followed by the disturbed then less-disturbed sites. After further investigation, the less-disturbed sites were found to have significantly less total annual precipitation which greatly impacted overall plant composition. As such, the less-disturbed sites were deemed inappropriate for comparison and the restored sites trajectory assessment was thus more focused on comparisons to the disturbed sites. The restored site was found to have lower moisture heterogeneity but higher hydrologic connectivity compared to the disturbed sites, traits more definitive of wet montane meadows. Species richness, status, plant type, and wetland classifications at the restored site were also more definitive of wet montane meadows compared to the disturbed sites. However, the restored site did have concerning areas of exotic species, especially in drier soils. Currently, rewetting techniques applied appear to be successful. Although, it is clear that adaptive management is needed to address issues of concern and help keep a continued positive ecological trajectory at this restored site, especially when heading into an uncertain future.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences
- Creator:
- Buchholtz, Clara
- Description:
- Tamalia coweni is unusual among gall-forming aphids in that it will often share its gall space with other members of its species, even as this has been shown to lower its fitness. Previous research utilizing manipulated densities of T. coweni on inflorescences of its host plant has indicated that population density is a strong predictor of gall-sharing rates, while kinship appears to be less predictive. The current study expands on this finding by investigating gall-sharing rates under natural population density conditions in leaf galls. In addition, it does an initial examination of whether gall-sharing correlates with preferential or optimal galling sites, and in line with the preference-performance aspect of the Plant Vigor Hypothesis (PVH). Cofounding rates were found to strongly align with those from studies using artificial aphid densities, and population density was shown to be a strong predictor of cofounding rates in a natural setting. Although strong patterns showing basal leaf positions were more frequently chosen as galling sites than distal ones, there was no evidence these sites were more likely to be cofounded. Over all, gall and cofounding distributions did not show a strong alignment with the PVH. Instead, other factors, notably timing, may offer more promising explanations, and offer a rich set of questions for further examination.
- Resource Type:
- Thesis
- Campus Tesim:
- Chico
- Department:
- Biological Sciences