Search Constraints
Filtering by:
Department
Biology
Remove constraint Department: Biology
Collection
Thesis
Remove constraint Collection: Thesis
« Previous |
1 - 50 of 935
|
Next »
Number of results to display per page
Search Results
- Creator:
- Hernandez, Trang Manny
- Description:
- There is a possibility to eradicate infectious diseases with antibiotics. However, new infectious diseases are continually being identified and some known pathogens are again becoming a threat because of antibiotic resistance. Amphibians mostly live in a moist environment which is the best condition for the growth of bacteria and fungi as well. Antimicrobial peptides produced by serous glands in the amphibian skin play a key role in limiting microbial growth and preventing infections with pathogenic microorganisms. In addition to the antimicrobial peptides produced by serous glands, microbial symbionts on the bullfrog skin are also a source of antimicrobial peptides that can protect the amphibian against diseases. In this research, we investigated whether cutaneous bacterial species isolated from Rana catesbeiana (North American Bullfrog), an amphibian species that is resistant to chytridiomycosis, produce secondary metabolites that could be used to inhibit the growth of three species of dermatophytes (Microsporum gypseum, Epidermotphyton floccosum, Trichophyton mentagrophytes) which are known to cause skin infections in humans. The isolated bacterial species from R. catesbeiana may be useful as producers of antifungal metabolites that kill, or inhibit the growth of, dermatophytes known to cause topical or subdermal skin infections in humans.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Lewis, Ryan D.
- Description:
- Purpose of the Study: The endangered Sonoma County population of the California tiger salamander, Ambystoma californiense, undergoes migrations between breeding pools and upland dry-season refugia. Orientation in this species during breeding migrations has been addressed minimally in previous studies, and literature is particularly sparse concerning newly metamorphosed juveniles. Previous works have not addressed the ability of metamorphs to orient or the way in which they search for upland refugia. The purpose of this study is to evaluate if California tiger salamander metamorphs can re-orient during initial migration and if search movements constitute a Correlated Random Walk. Procedure: We evaluated fine scale movements of newly metamorphosed California tiger salamanders as they moved away from breeding pools, by capturing salamanders with a drift fence. Metamorphs received different orientation treatments, and subsequent movement was tracked with fluorescent powder. We measured turning angles and step lengths at each segment of the tracks, and compared the effect of different treatments. Findings: Here we show that newly metamorphosed juveniles can re-orient to their upland migration path after being interrupted and disoriented. Further, we demonstrate that while searching for burrow refugia, metamorph movement is a correlated random walk. Conclusions: The initial migration from natal pools to uplands following metamorphosis has been identified as a crucial life history juncture for the persistence of this species. Our findings show that these migrations are directed by some orientation, and that these movements are not random. The presence of a Correlated Random Walk is consistent with search patterns in many vertebrates.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Grimes, Adam John
- Description:
- The blunt-nosed leopard lizard (Gambelia sila) is a federally and state-listed endangered species, endemic to the San Joaquin Valley, Carrizo and Elkhorn Plains, and Cuyama Valley of central California. Habitat degradation has had a profound impact on the historic distribution and population size of G. sila. Although recognition of G. sila as a distinct species has been questioned by some authors (e.g., Cope 1900, Smith 1946), it is currently recognized as a full species separate from the wide-ranging long-nosed leopard lizard (G. wislizenii); however, genetic support for the specific status of G. sila is lacking. Furthermore, the genetic identity of leopard lizards in the purported hybrid zone between these two species in the Cuyama Valley in Santa Barbara and Ventura counties has not been evaluated using modern molecular techniques. Understanding the genetic identity of leopard lizards in the Cuyama Valley has practical as well as systematic implications. I investigated the sister taxon relationship of G. sila and G. wislizenii using 603 base pairs of sequence from the mitochondrial cytochrome oxidase III (CO3) gene from 37 individuals representing the two species sampled from various populations in western North America. Phylogenetic analysis revealed 17 haplotypes that are partitioned into two major clades that correspond to the range of G. sila and that of G. wislizenii haplotype groups, thus supporting the recognition of both lizards as distinct species. Additionally, I sequenced 682 base pairs of the mitochondrial cytochrome oxidase b (cyt b) gene from 34 individuals representing six populations of G. sila, including lizards from a remnant hybrid population. Phylogenetic analysis indicated that the cyt b sequences consisted of 18 haplotypes that are partitioned into three geographic clades: northern, central, and southern. All lizards from the Cuyama Valley exhibited the G. sila mitochondrial DNA signature and formed the "southern" clade that was joined as a sister group to the "central" clade. My morphological analysis placed some leopard lizards from the hybrid zone with true G. sila, whereas some aggregated with G. wislizenii, indicative of hybrid status. However, genetic signatures suggest that all lizards in the hybrid zone are true G. sila, and not hybrids.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Tennant, Erin Nicole
- Description:
- The Tipton kangaroo rat (Dipodomys nitratoides nitratoides), is an endangered subspecies of the San Joaquin Valley kangaroo rat, found in the Tulare basin of the San Joaquin Valley. Dipodomys n. nitratoides and the larger Heermann’s kangaroo rat (Dipodomys heermanni) are often found sympatrically throughout the San Joaquin Valley. However, potential competitive interactions and the nature of population fluctuations between these two species are largely unknown. Because I thought that D. heermanni could be negatively affecting a translocated population D. n. nitratoides on Allensworth Ecological Reserve, Tulare County, California, I initiated a study on potential competitive interactions between these two species. In this study my objectives were to (1) determine whether the presence of D. heermanni affects space use and foraging behavior of D. n. nitratoides and (2) compare D. n. nitratoides abundance and population trends between areas with and without D. heermanni. I found that in an exclusion area where D. heermanni were removed, D. n. nitratoides increased exponentially since the start the study, whereas on a control site with both species, D. n. nitratoides decreased significantly. My results suggest that D. heermanni are competitively depressing a population of translocated D. n. nitratoides on the study site. Furthermore, eliminating competitive effects of larger, coexisting species during reintroduction or translocation efforts for D. n. nitratoides may be an important factor in success. To further test optimal translocation and reintroduction methods for protected kangaroo rats in the San Joaquin Valley, possibly an important conservation strategy, I translocated the group of non-protected D. heermanni that was removed from the exclusion area during the competitive interactions part of my study. During this part of my research, my objective was to determine whether soft-release methods, which involve a 30-day acclimation period in a wire mesh cage, help to improve survivorship of translocated kangaroo rats. My results indicated that hard-released individuals had higher survivorship than soft and semi soft- released individuals. I believe that one of the factors that may have contributed to the success of hard-released individuals was the high number of available burrows on the translocation site, often not found at sites, which provided refugia for translocated individuals. ii
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Keldgord, Heather Elayne
- Description:
- Rhus ovata is an evergreen shrub species that is common to low elevations in southern California. This species is subdioecious, i.e. some individuals are functionally females and produce fruit while others are functionally male and produce flowers with pollen. I hypothesized that because female plants allocate greater resources to reproduction through the formation of both flowers and fruit, female plants have fewer resources available for vegetative growth, survival, and defense. Therefore, I predicted that female plants would be smaller and less competitive. I sampled Rhus ovata populations at six sites across a rainfall gradient (221mm/yr to 701 mm/yr) and predicted that populations would be male dominated at drier sites because of their greater stress tolerance. At each site I measured the ratio of male to female plants within the sampled population. For a subset of individuals at each site, I measured crown size, stem tissue density, specific leaf area, reproductive investment, and distance to the nearest neighbor. As expected, female plants had greater total reproductive investment although the amount of investment was highly variable and females exhibited more variability than males. However, this differential reproductive investment did not lead to sexual size dimorphism. Ratios of functional male plants to functionally female plants differed among sites, but these differences were not correlated with rainfall and across sites the ratio of males to females did not significantly differ from a one to one. Plasticity in allocation to reproduction among females in this long-lived woody species may mitigate reproductive costs and reduce sexual dimorphism.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Atwood, Robert Christopher
- Description:
- Opuntia basilaris Engelm. & Bigelow var. treleasei (J.M. Coult.) Toumey (OBT), commonly known as Bakersfield cactus, is endemic to parts of Kern County, California. O. b. var. treleasei is one of four varieties of Opuntia basilaris and is state and federally listed as endangered (USFWS 1990). The purpose of this study was to assess the genetic differentiation between OBT and Opuntia basilaris var. basilaris (OBB), and within and among populations of OBT throughout its range. Samples were collected from 200 individual plants representing 32 populations of OBT and one population of OBB and were analyzed using amplified fragment length polymorphisms (AFLP). The AFLP protocol was successfully used to differentiate between an outgroup population of OBB and the great majority of the sampled populations of OBT using 195 polymorphic fragments. Two dendrograms were created using unweighted pair group method with arithmetic mean (UPGMA); one for all individuals and the other where each population was treated as a discreet unit. In the dendrogram based on all individuals, most samples did not cluster as distinct geographic populations, suggesting little genetic differentiation, due to a partial or complete restriction of gene flow, among the majority of OBT populations. Extensive genetic variation was found within and among OBT populations based on an analysis of molecular variance (AMOVA). Twenty three percent of the genetic differentiation was found among fragmented populations and 77%from within individuals of OBT populations suggesting that genetic variation exists between individuals within the OBT populations analyzed. In the UPGMA diagram by population, all five of the Wheeler Ridge populations clustered together. Moreover, three of the Wheeler Ridge populations formed a distinct cluster in a principal coordinates analysis (PCoA) suggesting some level of genetic structure among OBT populations. The only population with a large sample size where virtually all representative samples grouped together was for ‘OEO2’, which is located in the eastern portion of the Southern San Joaquin Valley. The results of this population genetics study will likely be useful in the conservation management of this endangered taxon.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Castaneda, Alejandro Realivazquez
- Description:
- The purpose of this study is to investigate the level of genetic divergence among populations of Vaejovis confusus in the southern San Joaquin Valley and across the state of California. Although there has been considerable research to measure genetic variation among and within scorpion species, little work has been done to investigate the impact of anthropogenic factors on genetic variation within populations. Anthropogenic factors such as man-made barriers can fragment populations and may serve as mechanisms of reproductive isolation. Particularly in the southern San Joaquin Valley, vast arrays of canals and artificial channels have been constructed to divert water from the Kern River for agricultural purposes. In the southern San Joaquin study, the level of genetic divergence is examined in a fragmented population as a result of an anthropogenic barrier, the California Aqueduct, at Coles Levee Ecosystem Preserve. Sequencing of the mitochondrial 16S ribosomal RNA gene in 20 Vaejovis confusus individuals of each fragmented population was performed. Neighbor-joining and maximum parsimony analysis of DNA sequences elucidated the level of genetic divergence. For comparison, an identical analysis was performed across a natural barrier, the Kern River at the Panorama Vista Preserve, which has separated Vaejovis confusus populations for a much longer period of time. The results of this study showed the presence of five haplotypes at the Coles Levee Ecosystem Preserve, with three haplotypes common to both sides of the California Aqueduct. Similarly at Panorama Vista Preserve, five haplotypes were found, with two haplotypes shared at both field sites across the Kern River. These results indicate that scorpion populations across the California Aqueduct and Kern River are not genetically partitioned, despite the isolating effect of these barriers. The existence of the California Aqueduct for over 50 years is not enough time to cause genetic divergence among fragmented populations. The occasional drying of the Kern River may promote gene flow between the populations or amount of time after reproductive isolation may be insufficient to cause evolutionary divergence between the two populations. In the California analysis the mitochondrial 16S rRNA gene is examined in 22 individuals from 9 counties to determine the effects of isolation by distance on the geographic-genetic structure of Vaejovis confusus populations. Scorpions were obtained from a collection of samples from the California Academy of Sciences, San Francisco. Neighbor-joining and maximum parsimony analyses were used to resolve the level of evolutionary relatedness among the populations of Vaejovis confusus throughout California. Fourteen haplotypes were found in this analysis. Eleven haplotypes were unique to their field site, whereas three were common across the state across large geographic distances (approximately 350 miles). Mitochondrial markers found high genetic variation (9.6%) in this species. Nearly half (154/325) of pairwise distance comparisons showed a 2.0% or higher sequence divergence and supported an overall isolation by distance effect. The occurrence of three haplotypes across the state results in a weak association between geography and genetic structure of V. confusus. Notably however, there is some geographic partitioning between haplotype D common in western California and haplotypes A and C common in eastern California. However, the overall lack of genetic partitioning with respect to geography among the California populations is likely due to an insufficient amount of elapsed time to promote genetic differentiation.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Hayes, Christine C.
- Description:
- The phorid fly genus Apocephalus is the largest assemblage of ant-parasitizing Phoridae. Apocephalus is currently organized into two subgenera: A. (Apocephalus) and A. (Mesophora). The species of A. (Mesophora) attack a wide variety of non-ant hosts including stingless bees, spiders, wasps, bumble bees, and cantharoid beetles. The species of A. (Apocephalus) are the true “ant-decapitating flies” and are divided into six species groups: the A. attophilus group (parasitoids of attine leaf-cutting ants), “A. miricauda group” (parasitoids of ponerine ants), A. pergandei group (parasitoids of Camponotus carpenter ants), A. mucronatus group, A. feeneri group, and A. grandipalpus group. Here I report on a preliminary molecular phylogenetic study of Apocephalus, including representatives of both subgenera and exemplars of five currently recognized species groups. Maximum parsimony, maximum likelihood, and Bayesian phylogenies were inferred using four nuclear (AK, TPI, CAD, 28S) and four mitochondrial (12S, 16S, COI, ND1) gene fragments (4284 bp total). For all analyses Apocephalus was recovered as a monophyletic group relative to the outgroup taxa included in the study. In addition, subgenus A. (Mesophora) was recovered as a monophyletic group, but was not a sister group to the subgenus A. (Apocephalus).A phylogenetic hypothesis for exemplars of five Apocephalus species groups is presented and compared to hypotheses based on morphology.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Duquette, Marc Roland
- Description:
- With over 1,300 known species, the genus Megaselia Rondani is the largest phorid genus, largely the result of high cryptic diversity and a past tendency for researchers to lump species into the genus that defied convenient classification. For many of these species, little information is available beyond one or two morphological characters. The first molecular study of such a species, Megaselia sulphurizona Borgmeier, is presented here. New sequence data from two mitochondrial loci (cytochrome oxidase, COI; NADH 1 dehydrogenase, ND1) for a total of 792 bp were obtained from 22 M. sulphurizona specimens collected from four populations in California, plus 12 other phorid taxa using standard DNA extraction and PCR techniques. Neighbor-joining, maximum likelihood, and maximum parsimony analyses revealed M. sulphurizona to be a cryptic species complex, constituting three distinct species in the Riverside, Monrovia, and Bakersfield/Tehachapi areas. These findings suggest greater cryptic diversity within M. sulphurizona, and have broader implications for phorid biodiversity.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Blackhawk, Nicole Cherri
- Description:
- The Giant Kangaroo Rat (Dipodomys ingens) is a federally and state-listed endangered species, endemic to the San Joaquin Valley, Carrizo and Elkhorn Plains, and the Cuyama Valley. Populations of the endangered Giant Kangaroo Rat (Dipodomys ingens) have decreased over the past 100 years because of habitat fragmentation and isolation. Changes in the population structure that can occur due to habitat fragmentation can significantly affect the population size and the dispersal of these animals. Dr. David Germano and I collected small ear clippings from male and female Giant Kangaroo Rats from six sites along the southern San Joaquin Valley to determine the genetic population structure of this species in this part of their range. We predicted that geographic distance and isolation of populations would decrease genetic relatedness compared to populations closer together. Having a better understanding of the genetic structure in this species will help with conservation actions, such as translocating individuals within the range of the species. These data were compared to published estimates of genetic diversity of Giant Kangaroo Rats in the Carrizo Plain to the west and the Panoche area to the north, the other large population centers of this species.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- MacKinnon, Evan D.
- Description:
- Non-native grass invasion is a major concern for land management and native plant conservation. In the southern San Joaquin Valley of California, human-disturbed environments that are heavily invaded by non-native grasses often contain some native annual species. These “weedy” native species apparently have the functional traits and life history characteristics to compete and persist in disturbed and invaded landscapes. We categorized several native plants into either a weedy or non-weedy habit based on several criteria, and confirmed this habit designation using a field trial where we controlled for other factors likely to influence species abundance under field conditions. We then measured functional traits for a group of five non-weedy species that occur locally but are not abundant in invaded areas, to a group of four weedy plant species that included the invasive grass red brome. We hypothesized that a suite of functional traits would define the weedy plant habit. We examined this hypothesis in a specific community, where we compared functional traits between weedy and non-weedy plant habits, and between native species and red brome. A principal components analysis (PCA) identified three distinct ecological clusters among the analyzed species (weedy native forbs, non-weedy native forbs, and grasses), and suggested the presence of a weedy functional type. Weedy species were different from non-weedy species in several traits (larger leaf area investment, larger root biomass allocation, heavier diaspores, and dormant seeds requiring cold-stratification for germination). The PCA suggested complementarity as an explanation for the co-occurrence of weedy native species and red brome, but individual trait similarities and a competition experiment suggested that competition can occur for some resources. Further understanding of the traits shared among weedy native plant species may lead to cost-effective approaches to restoring invaded landscapes.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Turnbull II, John
- Description:
- Examination of fish skeletal remains from archaeological sites serves both archaeological and biological interests. For archaeologists, it can establish the role of fish consumption in a people’s diet, provide clues to their fishing technology and overall maritime capability, and even suggest movement patterns and settlement (Rick et al. 2001, Erlandson et al. 2008, Des Lauriers 2010). Analysis of fish bones from excavations on San Miguel Island, of the southern California coast, suggested use of boats and early evidence of hook-and-line fishing techniques, concurrent with an estimate that fish comprised over 50% of the edible meat for the early islanders (Rick et al. 2001). Fishbone identifications have contributed to determining where early Paleocoastal peoples settled, to indicating occupation in some areas earlier than previously thought, and to suggesting that at least some southward Pacific coastal migration in North American may have been by sea (Erlandson et al. 2008). For ichthyologists, identifications of fish remains provide a historical or prehistorical survey of fishes in an area, and with comparison to modern surveys of those same areas, provide bases for examining fish distribution, fish diversity, and marine habitats over time (Gobalet 2000, Salls 2000, Erlandson et al. 2008). In supporting Point Conception, California, as a landmark for a marine faunal break, Gobalet (2000) compared the distribution of fishes identified from the archaeological record to their current distributions. Salls (2000) used bone identifications from archaeological sites on Southern California’s San Clemente Island to describe probable offshore habitats for as early as 9,000 calendar years before the present (cal BP). For over a decade, archaeological excavations on Cedros Island, which lies off the Pacific coast of the Baja California peninsula, have unearthed evidence of early colonization in the Cedros area, with implications for Paleo-human migrations (Des Lauriers 2010). Unfortunately, no on-site scientific survey of the fishes or marine habitats at Cedros Island has been published against which to compare fishbone analysis, but modern surveys of the waters close to Cedros Island exist and can be useful. Regarding habitats, Quast (1968), Engle (1993), and Bond et al. (1999) represent influential earlier studies that established the use of fish species associated with specific habitats. More recent marine faunal surveys that included the Cedros marine environment (but not specifically Cedros Island) also describe fish assemblages associated with habitats. Stephens et al. (2006) examined such associations for the rocky reef/kelp bed habitats of the southern San Diego Province, as did Pondella II et al. (2005) for the San Benito islands that lie close to Cedros. Allen and Pondella II (2006) provided a comprehensive ecological review of the California coast south to central Baja and identified fish species associations with a wide range of habitats. In this thesis, I report the identifications of fish bones from archaeological excavation sites on Cedros Island. The archaeological investigation indicates the settlement of the area about 12,000 cal BP and the establishment of a society that existed into the 18th century of our current era (CE; Des Lauriers 2005, 2008, 2010). These identifications then are provided to assist this investigation on Cedros in its efforts to better understand the Cedros islanders and to lend some insight as to the types of fishes they harvested and the predominant habitats those fishes represented.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Madsen, Angela
- Description:
- Ecological interactions can vary in strength depending on environmental conditions. The outcomes of these interactions are often dependent on the abiotic environment, but can also depend on the presence of other biotic species, including mutualists, which can further alter these effects due to trade-offs in nutrient allocation for multiple interactions. For example, some plants produce extrafloral nectar, a specialized nectar used to attract ants that will defend the plant against herbivory. If plants with extrafloral nectaries also have a second mutualistic relationship with the soil bacteria rhizobia, this second mutualism has been shown to alter the attraction of ants to the extrafloral nectar of the plant. This change in ant attraction could be caused by changes in nectar production or nectar composition, although the exact reason is unknown. Plants do alter extrafloral nectar production and composition for other reasons, for example if a plant is experiencing herbivory the plant will increase the quantity of the extrafloral nectar which will attract more ants. What is not well understood is what specific changes to the nectar, if any, cause it to become more attractive or if the attraction is simply due to a higher quantity of the extrafloral nectar. In my thesis research I explored how the chemical composition of extrafloral nectar, specifically nectar quantity and sugar, is affected by rhizobia mutualists, soil nutrients, and herbivory. Moreover, I explored how these changes influence the ant community and herbivorous arthropod community, as well as plant traits and overall fitness of the Vicia faba plant and its associated mutualistic rhizobia. I tested the effects of these factors through a series of greenhouse and field experiments, running the extrafloral nectar through a total carbohydrate assay to quantify carbohydrate (i.e. sugar) content. I found that under most conditions, the composition of the extrafloral nectar remained constant. However, when plants associated with the soil bacteria rhizobia, the rhizobia mutualism caused a decrease in sugar content in extrafloral nectar but increased the overall quantity of extrafloral nectar produced when outside of herbivory pressure. The reason for this could be due to limited resources, as the plant has a finite amount of carbon and has to allocate this carbon to both the extrafloral nectar and to rhizobia. This need for resource allocation and the altered quantity and composition of extrafloral nectar had no effect on plant fitness traits nor on ant or arthropod visitation in my study, although so few ants were present that conclusions on ant visitation effects cannot be made. These results allow for other new and exciting questions in plant and insect ecology, such as what effect these resource allocations have on plant competition, growth, fitness, and how it impacts the broader ecological community.
- Resource Type:
- Masters Thesis
- Identifier:
- 10091
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Castro, Viridiana
- Description:
- Transporting water efficiently is one of the chief functions of plant vascular systems. Highly efficient transport is generally beneficial; however, tradeoffs arise because vascular systems have multiple functional roles that interact with one another. One example of a tradeoff may be related to how plants respond to water deficits. Some plants growing in arid and semi-arid environments form xylem networks that are able to tolerate water deficiencies and cope with embolism spread. Distinguishing patterns in embolism spread is important to understand how plants are vulnerable to water stress and what tradeoffs are involved in water stress resistance. Flowering plants found in mediterranean-type ecosystems differ in conduit (vessels and tracheids) presence and abundance. Little is known about how embolism spreads in plant vascular systems and the role tracheids play in the spread of emboli in vessel-bearing plants. I hypothesized that patterns in vessel embolism spread are linked to the type of conduit connections. I assumed that the propagation of embolism most commonly occurs through vessel-to-vessel connections. Therefore, I predicted that the presence of tracheids minimizes embolism spread compared to species with only vessels that have greater numbers of vessel-to-vessel connections. By contrast, greater vessel-to-vessel connections promote greater hydraulic transport efficiency. To test this hypothesis, I quantified embolism spread using computer assisted tomography (microCT) and hydraulic efficiency (hydraulic conductivity per unit xylem area; Ks) in six different species of woody plants that differ in tracheid presence, vessel structure, and hydraulic function. In Chapter 1, I briefly review how plants respond to water stress and what effects have been noticed to occur within their xylem conduits as a result. In Chapter 2, I present microCT, hydraulic efficiency, and percentage loss in conductivity (PLC) results from dehydration treatments for six species native to mediterranean-type climate regions in California, Cercoparpus betuloides, Malosma laurina, and Heteromeles arbutifolia; and the Mediterranean Basin, Laurus nobilis, Olea europaea, and Cistus ladanifer. In Chapter 3, I summarize my findings in the broader context of plant vascular function. My chief conclusion is that the connections between vessels are a key determinant of the tradeoff between hydraulic safety from cavitation and transport efficiency.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Stevens, Samantha K.
- Description:
- Purpose of the Study: The Russian River watershed stretches across a significant portion of Sonoma and Mendocino counties, covering 1,485 square miles, and is home to not only humans, but countless fish and wildlife species as well. The Russian River valley is famous for being an ideal place to grow wine grapes and other agriculture, in part for its fertile soil, as well as the region’s Mediterranean climate. In addition to this, the Russian River is a year-round recreational hotspot for both tourists and locals alike. Maintaining a high quality of water in any area is important, and this is especially true when the local economy relies so heavily upon surface water. According to the North Coast Regional Water Quality Control Board, the entire Russian River watershed is impaired for sediment and temperature, and recent data also show pathogen impairment throughout the watershed. The Laguna de Santa Rosa sub-watershed is also impaired for phosphorus and dissolved oxygen, in addition to the impairments throughout the watershed (Russian River Watershed Overview, 2019). Land uses and water quality are interconnected in the Russian River watershed, but causal patterns between the two are not well understood. Procedure: Water quality data was obtained via the United States Geological Survey (USGS) and input into Microsoft Excel to generate time series graphs of different water quality constituents. The three sites selected are Jimtown, Digger Bend, and Hacienda Bridge. A model from the USGS ScienceBase inventory was utilized for this project, which consists of future land use, land cover, and population projections for the state of California for the period of 2001-2101. This model was projected as a layer in ArcGIS Pro in order to estimate the land cover changes based on low, medium, and high population projections for the years 2050 and 2100. In order to estimate the nutrient input for these different scenarios, models were constructed using WikiWatershed’s Model My Watershed tool. Within Model My Watershed, the land cover was altered to emulate the six models by adding polygons of the desired land cover, running the model, and observing the resulting nutrient and total suspended sediment load output. An additional aspect of this project is to conduct an analysis of policies. Findings: As land is developed into managed cropland, nutrients are typically added in order to increase production and profit. As a result, the runoff from cropland is typically nutrient rich when infiltration rates are low. Records from the Sonoma County Crop Reports indicate that the acreage of vineyards nearly doubled between 1990 and 2000. The exploration of potential land use and land cover changes through the projection of the USGS ScienceBase layers in ArcGIS and the modeling of nutrient load in Model My Watershed showed both an increase in agricultural land use as well as an increase in nutrient load, which is expected. The data obtained from the USGS Water Quality monitoring site did not show many points of interest or concern and generally followed a seasonal pattern. The policies in place in Sonoma County regulate both point source and non point source pollution, which is an extremely effective way to minimize polluted runoff from entering the streams and river in the Russian River watershed. The federal, state, and county regulations seem to be adequately minimizing point source agricultural pollution, and could benefit from increased riparian vegetative buffer zones to help slow the flow of polluted runoff, increase infiltration, and minimize the amount of nutrients that reach the waterways throughout the watershed. Conclusion: While this project did not result in a definitive answer as to what is causing the most nutrient pollution in the Russian River watershed, based on the findings of project, it is safe to speculate that total loads of suspended sediment, nitrogen, and phosphorus were lower throughout Sonoma County when there was less agricultural land use since the modeling data predicts higher total loads as agricultural land use increases. In addition to an increase in vineyard, the Sonoma County Crop Reports recorded a two - fold increase in the number of cattle in the county between 1990 and 2018.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Phalen, Carol Marie
- Description:
- Paralabrax clathratus, commonly known as the kelp bass, is an important sportfish to the Southern California angler, ranking among the top sportfish on commercial passenger fishing vessels since the 1950's. They commonly occur in a patchy distribution from Monterey Bay, CA to central Baja California, Mexico, preferring a habitat associated with structure. They are broadcast spawners and have the potential for high levels of gene flow during the 28-30 day pelagic larval stage. The purpose of this investigation was to determine the extent of genetic variation of the kelp bass at various locations throughout their range. Seven populations were examined for genetic variation and population subdivision using two variable molecular markers. Restriction fragment length polymorphism (RFLP) of the internal transcribed spacer regions (ITS) of the nuclear ribosomal DNA repeat unit revealed no genetic variation or geographic subdivision. Although direct sequence analysis of the 5' portion of the mitochondrial DNA revealed a high level of genetic variation , no geographic subdivision was detected based on neighbor joining, maximum parsimony, and analysis of molecular variance (AMOVA). These results suggest that a high level of gene flow exist among locations, most likely due to the dispersal of pelagic larvae via prevailing currents, episodic events, and adult movements.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Mohtashemi, Iman
- Description:
- Clusterin is a multi-functional protein that was initially isolated from ram testis. It was first identified for its ability to promote aggregation of cells, hence the name clusterin (Fritz et al., 1983). Subsequent research has identified clusterin in many mammalian fluids and organ systems. A number of functions have been hypothesized for clusterin from independent labs which produced a variety of acronyms. For example, clusterin has been shown to protect cells from the innate immune response such as complement mediated lysis , complement lysis inhibitor, CLI (Oda et al., 1995) and is also involved in cholesterol transport, ApolipoproteinJ, Apoj , (Gelisseb et al., 1998). It is the major secretory product from sperm cells (sulfated glycoprotein 2,SGP-2). It is also known as Testosterone repressed prostate message (TRPM) due to the fact that it is up- regulated after castration and is involved in apoptosis. The role of clusterin as a neuroprotectant has been investigated, however, data supporting a neuroprotective role remain under debate. In this report we combined immunoaffinity chromatography with HPLC to purify clusterin from human serum. We also utilized a clusterin knock-out model to determine the role of clusterin under toxic insults. A recombinant protein purification protocol was also developed.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Kuwadekar, Pradnya Sanjeev
- Description:
- Cell surface properties play an important role in embryonic morphogenesis and in malignant invasion. Cell surface sugar chains extend away from the cell membrane and are believed to be involved in cellular migration and adhesiveness. Some of these sugar complexes also act as receptor sites for lectins. Plant lectins are often used to detect these receptor sites on embryonic cells. At the 16 cell stage, sea urchin (Strongylocentrotus purpuratus) embryos exhibit cell size differentiation into larger cells (macromeres), medium sized cells (mesomeres) and smaller cells (micromeres). A difficulty in separating these embryos into single cells is the presence of a fertilization membrane. In this study, prior to fertilization the eggs were treated to prevent fertilization membrane formation. Following fertilization and development to the 16 cell stage, the embryos were disaggregated and the cell surface properties of the individual cells (macromeres, mesomeres and micromeres) were analyzed by their differential adhesiveness to agarose beads coated with various lectins. The results show that each of the three cell types of the 16 cell stage embryo have specific surface properties as indicated by their differential ability to bind to specific lectin beads. Moreover, the adhesive specificities demonstrated in this study for the 16 cell stage embryo differ somewhat from those of blastula stage embryos as reported in an earlier study from this laboratory. The results indicate that there is both a stage-specific and cell type-specific differentiation of cell surface sugar containing receptors that may be important in controlling morphogenetic events.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Abboud, Randa I.
- Description:
- Ammonia, glutamate, or glutamine can be utilized as sole source of nitrogen by Sporosarcina ureae. The growth rate is proportional to the concentration of ammonia up to a set value of 0.6 div./h at 84 mM, but concentration independent for glutamate at 0.5 div./h and glutamine at 0.33 div/h. When glutamate or glutamine is supplied as the sole source of carbon, energy, and nitrogen a diphasic type of growth is observed. Glutamate synthase (GOGAT; EC 1.4.1.13) is not detected in extracts of cells grown in tryptic soy yeast (TSY) medium nor in defined media containing acetate and ammonia, glutamate or glutamine; however, glutamine synthetase (GS; EC 6.3.1.2.) exhibits both biosynthetic and transferase activities at basal levels in extracts of cells grown under all growth conditions. A two-fold increase in the GS basal activity is observed in extracts of cells grown in ammonia-limited media. Two distinct glutamate dehydrogenases were detected and separated electrophoretically. One is specific for NAO (NAO-GOH; EC 1.4.1.2) and the other for NAOP (NAOP-GOH; EC 1.4.1.4). The NAO-GOH has an unusually high degree of thermal stability maintaining 95-100% of its activity after incubation for 15 minutes at 75�C; however, it irreversibly loses its activity upon freezing. The NAOP-GOH maintains 100% of its activity upon freezing but cannot survive the treatment at 75�C. The NAO-GOH exhibits increased activity in extracts of cells grown with glutamate as carbon and energy source, whereas the NAOP-GOH activity increases in extracts of cells grown in limiting ammonia concentrations. The Km values for glutamate in extracts of cells grown on TSY at pH 7.7 are 5mM and 30 mM for NADGDH and NADP-GDH, respectively. Two heat-labile glutaminases were separated electrophoretically; glutaminase ? is constitutive and glutaminase ? is repressed in complex media. Possible mechanisms of nitrogen assimilation in this organism are discussed.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Keshishian, Arbi
- Description:
- Many studies have examined the effects of free lectins such as Concanavalin-A (Con-A) on sea urchin development and suggested that lectin binding ligands play a role in embryonic cellular interactions. In this study, the effects of immobilized Con-A on sea urchin cellular interactions were examined by incubating embryos 2 hours after fertilization, 24 hours after fertilization right before invagination, and 27 hours after fertilization when invagination has occurred, with no Con-A beads, low, medium, and high counts of Con-A derivatized agarose beads and the embryos were observed at various times after beads addition. The results showed that archenteron development and attachment were interrupted when high and medium counts of Con-A beads were added before invagination. Once invagination occuffed, the Con-A beads had no significant effect on further development. The results were statistically significant (P < 0.0001) when archenteron attachment was compared between controls and experimentals when beads were added before invagination. There were no significant differences in the controls and experimentals when the beads were added after invagination (P>0.061). Analysis of protein concentration in the supematants from Con-A beads alone, beads with embryos, and embryos alone, suggested that small quantities on order of ug/ml of Con-A might have been released from the beads by the embryos, although it is very possible that no Con-A was released and what was released was sea urchin proteins resulting from cell lysis in the presence of Con-A beads. Further study of this issue is required to determine if immobilized Con-A (and not free Con-A) can effect specific embryonic cellular interactions in this system, an issue that is of importance in identifying mechanisms of morphogenesis.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Spiegler, Marci A.
- Description:
- The sea urchin is the material of choice for studying many early developmental events. Methods to extend the viability of sea urchin gametes have not received much attention, but it is well known that the eggs are easily damaged by freezing (4). This study was designed to extend the viability of Lytechinus pictus eggs and sperm without freezing. Gamete viability measurements were based on relative numbers of fertilized vs. unfertilized eggs, % fertilization and on observations of embryonic development. Results indicate that gametes can be stored longer and at lower temperatures than previously described (7) . Sperm were consistently kept viable for at least 11 days with little decrease in viability when stored in glass test tubes or plastic petri dishes and submerged in ice inside a refrigerator at 0�C � 1�C. In one experiment, sperm stored in glass test tubes on ice remained viable up to 20 days after extraction. Eggs were maintained from 1 to 7 days, rather than the one day or so previously reported (7) when stored in glass test tubes submerged in ice in a refrigerator at 0�C � 1�C. Results of egg and sperm experiments varied at different times in the season. Such variations may be caused by seasonal cytoplasmic changes (9), population differences, or the time mature individuals were maintained unfed in aquaria prior to use. Results from this study should be useful for a variety of research, mariculture, and teachin9 applications where sea urchin supplies are limited or when the same gamete population is required for subsequent experiments.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
22. Molecular cell adhesion modeling using nucleotide and carbohydrate derivatized beaded agarose resin
- Creator:
- Traxler, Vern S.
- Description:
- Cell adhesion has been studied for almost a century beginning with H.V. Wilson's classic studies on sponge cell aggregation. Cell adhesion plays an important role in morphogenesis and malignancy, but its molecular basis is poorly understood. As the cell surface often consists of hundreds of different molecules, it has been difficult to identify those molecular groups that function in the specific adhesion that occurs between cells. Students in this laboratory have approached this problem in a novel way. By examining the adhesion of agarose beads derivatized with only one type of molecule, one can learn more about which molecules, when isolated from all others, can adhere and which cannot, under conditions of the assay. Approximately 20,000 molecular combinations are being tested for adhesion in this laboratory. This thesis describes the work on 570 combinations of nucleotides and carbohydrates, each repeated at least three times. Although there is no evidence that interactions of these molecules are involved in cell adhesion, or even that nucleotides commonly occur on cell surfaces, it was important to examine all available molecular combinations because they may offer clues about the types of bonds that can form stable adhesions. For example, if nucleotides and carbohydrates adhered to each other via hydrogen bonding, this would provide evidence that hydrogen bonding can mediate adhesion. Fifteen different nucleotide derivatized beads were crossed with thirty-eight different carbohydrate derivatized beads and examined for adhesion to each other in distilled water and artificial sea water. All combinations that displayed any positive adhesion were repeated by at least two individuals. All 570 bead combinations did not adhere under the conditions of the assay, indicating that this set of nucleotides and carbohydrates did not form bonds stable enough to hold cell sized particles together. Previous experiments in the lab have shown that certain bead combinations could adhere under these conditions, leading to hypotheses concerning adhesion mechanisms that are being tested in living systems (Acta histochemica 98:441-451, 1996). The negative results presented in this study are meaningful in improving our understanding of what types of molecules can or cannot form stable bonds in a cell-like model system that allows the study of isolated molecular combinations.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Nosrati, Dorit
- Description:
- Iranian Jews constitute a growing minority in metropolitan cities around the United States. They are part of a close-knit community, with strong family and cultural values. Prevailing negative attitudes in the Iranian Jewish society towards disease and disability often cause the isolation and rejection of individuals with impairments. Having a child with a genetic disorder or a birth defect is to be avoided at any cost, since it may bring shame upon the entire family. There is limited information available in the field of genetic counseling about the Iranian Jewish community. Since prenatal choices reflect a person's cultural and social understanding of birth defects and genetic disorders, increased awareness of the community's values and characteristics is valuable in providing culturally sensitive genetic counseling services. The purpose of the study was to explore factors that play a major role in prenatal choices and that influence perceived causes of disabilities among Iranian Jews living in the United States. I hypothesized that a direct correlation exists between (a) acculturation, (b) education, (c) religious affiliation, and personal reproductive choices and perceived causes of disabilities in this population. A four-part questionnaire was designed based on self-written questions, and a pretested and validated instrument. The questionnaire assessed demographics, beliefs about causes of birth defects and genetic disorders, personal reproductive choices, and acculturation. The overall participation rate was 55%. Participants were 74 male and female Iranian Jews living in the greater Los Angeles area. Data were analyzed separately for male and female participants. The majority of participants were Conservative Jews, single, educated, and childless. The survey data showed low degree of acculturation, with the vast majority identifying themselves as either bicultural or Iranian. Among female and male participants, the study showed a strong correlation between (a) acculturation, (b) education, (c) religious affiliation, and personal reproductive choices. Among females only, the study also showed a strong correlation between these factors (acculturation, education, and religious affiliation) and perceived causes of disabilities. The correlation analysis showed that acculturation, education, and religious affiliation play roles in influencing prenatal decision-making. Therefore, it is important to explore these issues in the genetic counseling session, and consider their influence on the client's prenatal choices.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- DeCilla, Patricia Lucy
- Description:
- The purpose of this study is to determine whether the level of folic acid (FA) in human blood serum affects the number of fragile sites observed in cultured T-lymphocytes. Private practice patients (Internal Medicine) who evidenced no symptoms of significant disease, but did exhibit low levels (less than 5 ng/ml) of serum FA, were asked to participate in this study; 10 consented to do so. Each provided a blood sample that was prepared for a quantitative cytological study of fragile-site expression in their dividing lymphocyte chromosomes. Then, each patient was given supplementary FA (10 mg/day) for 2 months, when a second blood sample was drawn so that an "after" fragile-site determination could be made and compared with the "before" figures. The data, as a group, show that there is a significant decrease in the number of fragile sites after FA supplementation. Evidence in the literature suggests that fragile sites on chromosomes may have a connection to cancer by predisposing to chromosome breaks and thence to rearrangements characteristic of cancer cells. Therefore, FA supplementation may not only serve to decrease fragile site expression but possibly reduce cancer incidence.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- LaGrave, Danielle
- Description:
- The homocystinurias are a group of autosomal recessive disorders which are caused by various inborn errors of metabolism. Tnese disorders are characterized by high plasma and urinary ieveis of homocysteine and methionine, and low levels of cysteine. The most common cause of homocystinuria is a defect in the enzyme cystathionine f3-synthase (CBS) which converts homocysteine to cystathionine. Patients who are homozygous for CBS deficiency can be responsive or non-responsive to pyridoxine (vitamin B6), a cofactor of CBS. BB-responsive patients usually have a milder clinical phenotype and later onset of symptoms as compared to B6 non-responsive patients. The common clinical manifestations of homocystinuria are ectopia lentis, skeletal abnormalities and osteoporosis, and mental retardation. The skeletal features and eye findings of patients with homocystinuria are very similar to those of patients with the more common genetic disease, Marfan syndrome, an autosomal dominant disorder affecting the connective-tissue fibrillin. Pneumothorax, relatively common in Marfan syndrome, is rarely seen in homocystinuria. In this paper I describe a patient with pyridoxineresponsive homocystinuria and repeated spontaneous pneumothoraces.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Sperou, Emily S.
- Description:
- Purpose of the Study: Long-lived iteroparous females may suppress reproduction during unfavorable conditions to maximize lifetime reproductive success. Capital breeders must accrue sufficient body reserves to support reproductive effort or they may exhibit reproductive failure. The basis of these reproductive decisions is not well understood. Northern elephant seals are seasonal, colonial breeders with a period of embryonic diapause and biannual foraging trips divided by a breeding and molting haul out. Being capital breeders, they use the post-breeding foraging trip to recover body mass lost during lactation and the gestational foraging trip to accumulate resources for lactation. Females exhibit high natality, roughly 15% of females skip breeding each year. A previous study suggested alteration in baseline cortisol concentrations may be the proximate mechanism linking foraging success and reproductive suppression, but evidence of an interaction between cortisol and reproductive hormones is currently lacking. Procedure: We investigated a suite of reproductive hormones (progesterone, 17β- estradiol, inhibin A, prolactin) and cortisol, to determine patterns across life-history stages. We analyzed 1,029 serum samples from 441 adult female NES during their biannual haul outs. Included in this dataset were 30 females known to have skipped breeding. Findings: The data confirmed a highly seasonal pattern to changes in sex hormones. Estradiol and inhibin were high during the late breeding haul out, suggesting the timing of ovulation. Progesterone was highest at the end of the molt, indicating implantation had occurred. Path analysis revealed strong influences of estradiol and prolactin on progesterone, indicating these three hormones are key for implantation. Individual variation suggests important regulatory roles for prolactin, inhibin, and cortisol in modulating implantation. The data suggest that some females suppress implantation under the modulation of cortisol and inhibin. Most females that skip breeding appear to implant but fail to maintain gestation. Conclusions: Failure to recover body reserves from the preceding reproductive event may inhibit implantation, but most non-breeding females fail to maintain pregnancy during the gestational foraging trip. This bet-hedging strategy is likely one component of a capital breeding life-history that buffers females against short-term changes in foraging success, but limits fitness costs to reproduction through multiple check-points for body reserves.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Hudson, Daniel
- Description:
- Purpose of the Study: To understand male and female mate choice patterns affecting species and gender recognition via long distance chemical cues, this study examined the rough skin newt, Taricha granulosa, in both pond and creek habitats. Response to chemical cues of males vs. females was examined for T. granulosa, whereas the California newt (Taricha torosa), and the red-bellied newt (Taricha rivularis) were used to examine how T. granulosa would respond to heterospecific chemical cues as compared to conspecific cues in a region of the species’ ranges where all three species occur in sympatry. Methods: To simulate mate choice decisions in nature as closely as possible, we conducted behavioral experiments in the field using a Y-maze apparatus (olfactometer). All trials were run in the field using unique individuals. Data were combined across multiple years. Mate choice was analyzed using a nominal logistic regression model accounting for variation among year, researcher, Y-maze apparatus, sex, and species. Findings: T. granulosa females chose chemical cues of conspecific males significantly more than heterospecific males, whereas males showed no preference between chemical cues of conspecific and heterospecific females. In addition, T. granulosa males chose chemical cues of conspecific males over conspcific females, whereas females showed no preference between chemical cues of conspecific males and females. Conclusions: The results of this study support long-standing theoretical paradigms that males, who have less parental investment in offspring will adopt a strategy of seeking matings with females regardless of quality, whereas females, with greater levels of parental investment, will engage in a more discriminating mate choice strategy. In this case, females use chemical cues to avoid heterospecific males during breeding season encounters and reduce wasting her singular mating event on an act of hybridization. A result of this mating strategy is that reinforcement of reproductive isolation is maintained in this region of sympatric range overlap. In contrast, will mate with any female across multiple mating events, and use chemical cues to either locate females or to avoid other males (or both).
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Tercero, Anthony D.
- Description:
- The perciform suborder Notothenioidae is comprised of Antarctic and sub-Antarctic fishes, several of which have lost their ability to rapidly upregulate major heat shock proteins (HSP’s) in response to thermal stress. In fact, some notothenioid species have instead adopted a pattern of expression resembling ancestrally constitutive genes. It is possible that evolution in the Southern Ocean has selected for increased expression of molecular chaperones given the denaturing effect extreme cold temperature has on proteins. The selective pressures of the sub-zero water may have also favored duplication events that bolster quantitative output of chaperones via gene dosage effects. Given that newly duplicated genes are under more relaxed selective pressures, it is plausible that gene duplication preceded alterations in the regulatory regions of the inducible HSP genes, enabling altered regulation of such highly conserved gene products. To test for evidence of these mechanisms, gene copy number of ancestrally inducible and constitutive isoforms within the major heat shock gene families were characterized via qPCR and compared for the Antarctic notothen Trematomus bernacchii, which has lost the inducible HSR, and the non-Antarctic notothen, Notothenia angustata, which has maintained an inducible HSR. Results indicate duplication of inducible isoforms within the Hsp70 and Hsp40 superfamily have occurred in the genome of T. bernacchii. The findings from this study suggest adaptive gene duplications may have played a role in maintaining increased protein folding efficiency in the sub-zero waters of the Southern Ocean and provided a mechanism for the evolution of alternative regulation of these conserved gene families.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Rzucidlo, Caroline L.
- Description:
- Purpose of the study: Adipose tissue is essential to endotherms for thermal regulation and energy storage as well as functioning as an endocrine organ. Adipose derived hormones, or adipokines, regulate metabolism, energy expenditure, reproduction, and immune function in model systems but are less well studied in wildlife. Female northern elephant seals (NES) achieve high adiposity during foraging and then undergo natural prolonged fasts while breeding, lactating, and molting, resulting in large changes in adipose reserves. Procedure: We measured circulating levels of four adipokines, leptin, resistin, adiponectin, and kisspeptin-54, in 196 serum samples from female NES at the beginning and end of their breeding and molting fasts. We examined the relationships between these adipokines and life history stage, adiposity, mass, cortisol, and the immune cytokine interleukin 6 (IL-6). Findings: All four adipokines varied with life history stage. Leptin concentrations were highest during the beginning of the breeding haul-out and resistin concentrations were higher throughout the breeding haul-out compared to the molt haul-out. Adiponectin was highest during the beginning of both haul-outs and kisspeptin-54 concentrations were highest during the end of the breeding haul-out. Leptin, resistin, and adiponectin were associated with measures of body condition, either adiposity, mass, or both. Resistin, adiponectin, and kisspeptin-54 were associated with circulating cortisol concentrations. Resistin was strongly associated with circulating IL-6, a multifunctional cytokine associated with the innate immune response. Adiponectin was associated with glucose concentrations and may be a driver of tissue-specific insulin sensitivity during life history stages categorized by high adiposity. Increased cortisol concentrations late in lactation were associated with increased kisspeptin-54 which may play a role in initiation ovulation in NES. Conclusions: This study suggests dramatic changes in circulating adipokines with life history and body condition that may exert important regulatory roles in NES. Differences from biomedical model systems suggest the potential for modifications of expression and function of adipose-derived hormones in species that undergo natural changes in adiposity as part of their life-history.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- O’Gorman, Cory James
- Description:
- Purpose of the Study: California black oak, Quercus kelloggii, plays an important role in the lifeways of many indigenous tribes throughout California. Native peoples tend black oaks using Traditional Ecological Knowledge (TEK) to encourage the development and proliferation of specimen oaks. These mature, large, full crowned trees provide a disproportionate amount of ecosystem services, including acorns and habitat, when compared to smaller black oaks. Altered approaches to land management and the cessation of frequent low intensity cultural burns places these specimen oaks at risk from encroachment, forest densification, and catastrophic fire. Procedure: This project is a collaboration between Sonoma State University and the Native Advisory Council of Pepperwood Preserve. Data were collected from 55 specimen black oaks at Pepperwood Preserve in north east Sonoma County. Ecological variables were measured to identify abiotic and biotic drivers of growth habit, scorch height and fire fuels. A certain crown shape is desired by many of today’s traditional gatherers including those represented on the Pepperwood Native Advisory Council. Findings: Encroachment was found to have a significant negative effect on both canopy area (p=0.0027) and live crown ratio (p=0.0378). Encroachment did not affect surface and ladder fuel load accumulation since the Tubbs Fire in October 2017 (p>0.05). Neither surface and ladder fuels nor encroachment variables significantly affected scorch height on the specimen oaks (p>0.05) following the Kincade Fire. Conclusions: This work will allow for the reimplementation of TEK to nurture specific specimen black oaks at Pepperwood Preserve at the discretion of the Native Advisory Council and increase access to land and culturally significant plants by local tribal communities. This has far reaching implications on tribal peoples’ well-being, their ability to engage in cultural practices, and ecosystem health.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Molinaro, Holly
- Description:
- Hamadryas baboons (Papio hamadryas) live in a complex multilevel social system with the one-male-unit (OMU) at the core. OMUs consist of an adult alpha male with one or several adult females, their dependent offspring and sometimes a few follower males. Previous research has documented that OMUs form in four distinct ways in wild populations. In December 2015, Oakland Zoo introduced two juvenile males into the hamadryas baboon exhibit. At the time of this study, these males were approaching sexual maturity. The complex social structure of this species and the changing social dynamics that might result as they reach sexual maturity provide a unique opportunity to utilize social network analysis (SNA) methods to examine OMU formation in a captive setting with an eye towards potential management strategies. SNA is a visualization method of looking at social data that allows researchers to understand sociality in terms of the importance of each individual, any subgroups, as well as the larger overall group dynamic. Behavioral and proximity data were collected over a six-month period (July- Dec 2019). These data were then transformed into networks to analyze the two now subadult males’ behavior over time and the presence of any subgroups. I found that one of the subadult males formed his first OMU following one of the four pathways found in wild studies. Despite changing group dynamics, overall group cohesion remained unchanged. This study reveals hamadryas OMU formation patterns in captivity as well as suggests potential welfare management issues that might arise.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
32. Interactions among Sudden Oak Death, Fire Fuel Loads, and Climate in Sonoma County Oak Woodlands
- Creator:
- Hernandez, Manuel
- Description:
- Purpose of the Study: Understanding impacts of invasive pathogens and wildfire on forests is a major challenge facing scientists, land managers, and policymakers. In this study, I used a long-term plot network in eastern Sonoma County to disentangle the interactions among an exotic pathogen (Phytophthora ramorum), fire fuels loads and climate in oak woodlands. I investigated the interactions among: 1) sudden oak death (SOD) inoculum loads, disease prevalence and pre-fire surface and ladder fuel loads, 2) surface and ladder fuel loads and canopy condition, and 3) canopy condition and post-fire surface and ladder fuel loads. Procedure: From 2004-2016, measurements of disease prevalence, tree growth, tree mortality and tree survival were collected for the three most abundant SOD host tree species: coast live oak (Quercus agrifolia), California black oak (Quercus kelloggii), and California bay laurel (Umbellularia californica). In 2014, surface fire fuel loads were quantified, and airborne Lidar data were collected. Elevation, slope, average potential solar insolation, and topographic moisture index, and climate water deficit were also calculated for these plots to determine the interactions of microclimate and topography on pre-fire fuel loads. In 2019, I recorded tree mortality and survival of these same species and quantified surface and ladder fuel loads across 33 plots (15 x 15 m) with a range of burn severity following the 2017 LNU Complex Fires. To analyze the interactions among abiotic and biotic factors over time I created a hypothesized pathway to describe potential direct and indirect effects of oak mortality, disease load, microclimate, topography, climatic water deficit, pre-fire fuel loads, and canopy condition on post-fire fuel loads. I tested this pathway using a path analysis. Findings: I found that P. ramorum disease load had no effects on pre-fire fuel loading. However, oak mortality in 2014, indirectly affected by P. ramorum disease load, significantly increased the amount of large surface fuels, and decreased ladder fuels. Plot elevation and maximum temperature also had a positive correlation with pre-fire ladder fuel amounts. Pre-fire ladder fuels, in concert with drought intensity and slope interacted to effect canopy condition post-fire (in particular, percent canopy damage). Percent canopy damage was greater in less sloped plots with greater amounts of ladder fuels and increased drought severity. Pre-fire ladder fuels also had a significant direct effect on post-fire ladder fuels, whereas increased amounts of post-fire ladder fuels were observed in less-sloped plots with greater amounts of pre-fire ladder fuels and more percent canopy damage. Surprisingly, plots with increased fire severity due to increased fuels had increased re-sprouts and re-growth of U. californica trees immediately following fire. Conclusions: Current management practices in oak-woodlands include the removal of U. californica in the presence of oaks to reduce the potential P. ramorum inoculum load. My results support this practice, as SOD indirectly increases fire fuel loads, which may in turn increase both the future susceptibility of the ecosystem to fire and the severity of these future wildfires.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Ghavamian, Yasmeen
- Description:
- All zoos grapple with challenges of keeping captive animals engaged in natural behaviors, especially for bears which prove to be among the more challenging species to keep stimulated. In captivity, a common indicator of poor welfare is the presence of stereotypic behaviors. In this study, we test whether providing increasingly complex feeding enrichment decreases the duration of stereotypic behavior and increases enrichment interaction for three adult female sun bears (Helarctos malayanus) at Oakland Zoo in California. We compared the effects of two different feeding enrichment devices- presented to the bears at three complexity levels- on sun bear stereotypic behavior. After three weeks of baseline data collection when no complex enrichment was present, we introduced the complex enrichment three times a week per level over six weeks. In addition, we measured each bear’s interaction with the enrichment devices to examine the effect of complexity on enrichment use. Providing increasingly complex enrichment decreased the duration of stereotypic behavior when compared to the baseline phase. Across the six weeks, the duration of stereotypic behavior was significantly less on the complex enrichment days compared to the days when complex enrichment was absent. Increasing enrichment complexity had variable effects on enrichment use. Our results indicate that providing complex enrichment decreased the duration of stereotypic behaviors, however, the effects of complex enrichment did not carry over on the days when the enrichment was no longer present. These results suggest that providing increasingly complex enrichment may have a positive influence on the behavior of captive bears.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Chen, Sylvia
- Description:
- Worldwide, there are 65 million people that have epilepsy and approximately 200,000 additional individuals are diagnosed with epilepsy annually. There is no cure and currently available anticonvulsants, which are medications to treat seizures, are not universally effective. Additional studies are needed to generate better treatment options. Drosophila melanogaster provides a valuable and efficient model to study seizure disorders due to the low cost of maintenance, genetic tractability, and short lifespan, which allows for observation at various life stages. D. melanogaster also possesses similarities to humans on cellular and subcellular levels. These advantages allow the development of a model for the high throughput study of epilepsy. This study aims to induce single and multiple seizures and monitor locomotion, learning, and memory. The results from the negative geotaxis assay, which takes advantage of D. melanogaster’s innate climbing behavior, suggest that single seizure events have minimal impact, whereas multiple seizures result in deficits in visuo-motor/motor behavior. Additionally, a visual place learning assay was used to study the cognitive abilities and results suggest a single seizure event impacts learning and memory. Lastly, whole brain slides were made and determined lesions in brain tissue result from repeated seizure events. The significant findings from this research may contribute to improve therapeutics for epilepsy by providing a method of high throughput screening.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Gonzalez, Dalia Banesa
- Description:
- This study involved Drosophila melanogaster, the common fruit fly, as the model organism to study the behavioral differences seen in flies overexpressing the human tau protein throughout their adult life span. The tau protein (MAPT – microtubule associated protein tau) is linked to Alzheimer’s Disease (AD). It is seen in both humans and Drosophila and has been noted to decrease learning and cognitive abilities in both. This study aimed to look at the cognitive and behavioral difference seen as adult flies age. The adult flies were tested at three different ages (young, middle, elderly) in order to look for any progression declines in behavior as the flies aged and expressed the human tau for longer periods of time. The human tau was driven into two different areas of the brain (ellipsoid body, mushroom body) that have been shown to be important regions for learning and memory in insects. The flies were tested in two different behavioral assays, a visual place learning assay and a negative geotaxis assay, in order to quantify spatial learning and memory. Additionally, fluorescence microscopy was used to analyze the amount of tau present in the brain at different times of the adult’s life, which confirmed the increased expression of tau as flies aged. As tau-expressing flies aged, both visual place learning and memory were impacted. These flies also showed a decline in planning ability. The behavioral declines seen in this study can be correlated to patients with AD who also overexpress this abnormal tau protein. This study aims to create a better Drosophila melanogaster model for AD. Moreover, the findings of this study can contribute to a better model organism for AD, which allow us to test interventions prior to the onset of dementia.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Montiel, Christian M.
- Description:
- The Escherichia coli cAMP receptor protein (CRP) requires both DNA binding and RNA polymerase recruitment for its transcriptional activation function. The DNA recognition of CRP is performed by the F-helix (residues 180-185) and several F-helix residues (Arg180, Glu181, Gly184, Arg185) are well-characterized as to their importance in DNA binding. However, no apparent function has been known for the other two residues (Thr182 and Val183). In this work, I show that the position-183 amino acid (Val 183) is important for the transcriptional activity of CRP. First, Ala substitution at position 183 led to an increase in transcriptional activation activity. Second, CRP mutants altered at position 183 were created to show an inverse correlation between amino acid size and transcriptional activation activity (V183A > V183G > wild type CRP > V183I > V183M > V183F = no activity). Third, the loss of the activity in V183F could be restored by a smaller amino acid substitution (IleGly) at position 172, implying that it is the combined size of positions 172 and 183 which is important. A structural analysis of CRP reveals that the position-183 amino acid faces the opposite of target DNA and is in close proximity to the position-172 amino acid. The requirement of a small residue at position 183 is hypothesized to avoid steric hindrance to the position-172 residue as steric hindrance would misalign the nearby AR1 residues, leading to poor RNA polymerase recruitment and transcriptional activation.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Thomas, Jason Michael
- Description:
- Bacteria must be able to withstand a myriad of stresses from both their environment, and in the case of pathogens, from their host. Low molecular weight thiols serve as redox buffers to maintain a reducing environment in the cell and participate in various protective mechanisms, including detoxification of reactive oxygen and nitrogen species, resistance against electrophiles and antibiotics, and protection against environmental stressors. In this study, I analyze the transcriptome of two heterotrophic clinically relevant bacteria, Pseudomonas aeruginosa PAO1 and Staphylococcus aureus SAUSA300 and transposon mutants disrupted in thiol biosynthesis. The transposon mutants are disrupted in P. aeruginosa glutathione biosynthesis gene, gshA, and S. aureus bacillithiol biosynthesis gene, bshC. I also analyze the transcriptome of the autotrophic cyanobacterium, Synechocystis PCC 6803 as well as a knock-out mutant disrupted in egtB, which is involved in ergothioneine biosynthesis. P. aeruginosa gshA mutant is downregulated in type II and type VI secretion systems and upregulated in type III secretion systems while the S. aureus bshA mutant is downregulated in type VII secretion suggesting that thiols play a role in secretion of effectors. Strikingly, both P. aeruginosa and S. aureus switch to anerobic respiration with nitrate as the electron acceptor in the thiol mutants. A number of other virulence factors are also differentially expressed in these mutants agreeing with the attenuation of the mutants in disease models. In contrast, genes related to high light resistance, acid stress tolerance, and osmotic stress tolerance are downregulated in Synechocystis PCC 6803. This suggests that ergothioneine is involved in abiotic stress tolerance in the autotrophic bacteria. Overall, we demonstrate that LMW thiols are involved in a myriad of functions have not been previously identified.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Ajanel Gomez, Jehiel Abigail
- Description:
- Discovered in 2004, tunneling nanotubes (TNTs) are actin-based, bridge-like structures that allow the intercellular transport of cellular components, electrical signals, and pathogens. Thus, TNTs have been implicated in viral propagation, neurodegenerative diseases, and cancer. Most research has focused on examining the molecules within cells that aid in TNT formation and function, but little has been documented on the role that exogenous molecules have in TNT formation. Past research has determined that hydrogen peroxide (H2O2) induces TNTs in various cell lines; however, the amount of H2O2 used was above was high (100μM). The aim of this study was to establish if TNT formation can be induced by pathophysiological H2O2 concentrations. In addition, we also investigated glutamate, an inducer of actin-based filopodia in astrocytes, as a possible TNT inducer. The data obtained using fluorescence microcopy suggest that low concentrations of H2O2 and glutamate are able to increase TNTs in both HeLa and CAD cell lines. Furthermore, cells treated with low concentrations of H2O2 or glutamate showed an increase in the expression of Myo10, a protein that has been linked to TNT formation and function. Lastly, the data obtained with a microscope capillary single cell sorting system suggest that H2O2 and glutamate can induce the formation as well as the elongation of cellular protrusions in distances ranging from 14-96 μm. Altogether, these results provide useful insights regarding TNT formation pathways in cells as well as the exogenous molecules involved in the formation of TNTs.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
- Creator:
- Surber, Lisa L.
- Description:
- Research on animal movement patterns and factors that influence these patterns is vital to conservation of endangered species. The California Red-legged frog (Rana draytonii) is a threatened species native to California. Their rapid decline has been largely attributed to habitat loss and introduction of invasive species, including the American Bullfrog (Lithobates catesbeianus). The aim of this research was to compare the nocturnal habitat use and seasonal movement patterns of R. draytonii and L. catesbeianus. I conducted a radio telemetry study in Sonoma County, California and mapped the locations of 13 L. catesbeianus and 51 R. draytonii from May 2017 to June 2018. Using a mixed model, I evaluated the effects of species, sex, size and rainfall on frog movement rate and compared habitat use relative to a water source. Within this model species, size and sex were found to have significant effects on movement rate. Rainfall was not found to have a significant effect on movement rate for either species. When comparing nocturnal habitat movement, I found that in the summer months species occupy different places relative to water sources in a creek environment; R. draytonii position themselves higher and further away from the nearest open water than L. catesbeianus. My work suggests that there are significant differences between the seasonal movement patterns and nocturnal habitat use of native R. draytonii and invasive L. catesbeianus. These differences may be helpful to conservation practices facilitating the survival of threatened R. draytonii.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Sonoma
- Department:
- Biology
- Creator:
- Karabidian, Eddie
- Description:
- A variety of models of cell adhesion have been proposed by previous investigators; each depended heavily on details of the biochemistry of cell surface sugars. In this study, Lytechinus pictus sea urchin embryos were used to study the molecular mechanisms involved in cellular interaction. The interaction between the tip of the archenteron and the blastocoel roof during gastrulation in sea urchin embryos has been of interest to developmental biologists for over a century. This interaction is fundamental to morphogenesis. An understanding of the molecular mechanisms of the interaction between the archenteron and the blastocoel roof will be of major importance to the field of cell adhesion. These findings will provide a better understanding of what goes wrong in abnormal adhesive interactions, which may lead to diseases such as cancer. This is why the National Institute of Health (NIH) has designated the sea urchin embryo as a model system for studying basic mechanisms in human heath and disease. Here, we examined the effects of two glycosidases (sugar cleaving enzymes) on the surface of the sea urchin embryo cells. The enzymatic activities of two commercially prepared glycosidases were verified by direct chemical assays on known substrates as well as live and fixed sea urchin material to determine the interaction of the tip of the archenteron and the blastocoel roof. SDS-PAGE was carried out to measure possible protease contamination and the purity of the glycosidases. Azocoll test was also performed in order to check for cryptic protease activity. The results suggested there was no detectable smearing or degradation of the substrate and only minor levels of contaminating protease activity. In order to find out if sea urchin embryos have exposed glycans that can be degraded by α-amylase or α-glucosidase live and fixed embryos were disrupted and were used as substrates for these enzymes. A colorimetric assay with 3,5-dinitrosalicylic acid was used to measure the amount of maltose released. α-amylase enzyme did not release detectable amounts of maltose from embryos exposed to formaldehyde for long periods of fixation, but did release small amounts of maltose from live embryos or embryos fixed for shorter terms (1 day). These results suggest that the enzyme we use has specific sites of cleavage that may become inaccessible during long-term formaldehyde fixation. α-glucosidase released a small amount of maltose from the substrate sea urchin. To confirm that the sea urchin embryos do not release inhibitors of α-amylase and other glycosidases, mixed reactions were also conducted in which the defined substrates were tested in the presence of long-term fixed sea urchin embryos. The results suggested that there was no evidence of inhibition of these enzymes. I incubated glycosidases (active and denatured) on microdissected archenteron and blastocoel roofs in adhesion assays to learn if they directly inhibited the adhesive interaction. α-amylase had no effect, while α-glucosidase only substantially inhibited adhesion after 12 hours incubation. While glycans have been implicated in mediating this cellular interaction, this is the first study that directly implicates polyglucans with exposed 1,4 terminal ends in the adhesion of the archenteron tip and blastocoel roof.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Saxton, William Manning
- Description:
- Applications of a low-speed centrifuge rotor designed to separate whole cells at very low g-forces in partially reoriented, shallow density gradients are presented. The particle separation chamber was fabricated using Lucite so that gradient behavior and particle sedimentation could be monitored visually during rotor operation by using stroboscopic illumination. Runs were recorded on videotape for later study and frame-by-frame analysis. Rotor performance was tested using a model system consisting of polystyrene microspheres of known sizes and densities. The resolution obtained exceeded that of previously reported centrifugal separations. Cells from an ascites-grown tumor were separated into three discrete subpopulations. Cells comprising each subpopulation were characterized in terms of size distributions and sedimentation rates. Experimental results are discussed in relation to theoretical considerations about the behavior of particles in partially reoriented density gradients.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Trujillo, Andreina
- Description:
- Tunneling nanotubes (TNTs) have been recently discovered as an essential form of cell-cell communication in multicellular organisms. Although TNTs appear to be an important cell-cell signaling pathway, its mechanism of formation and functions are still not fully understood. A central issue is determining whether mitochondria play a vital role in the formation of TNTs. Previous studies have shown that exposure to a low concentration of ethidium bromide (EtBr) in mammalian cells caused a complete loss of mitochondrial DNA (mtDNA) leading to non-functional mitochondria (Rho0 cells); therefore, this technique will be applied to produce a HeLa Rho0 cell line to study the effects of non-functional mitochondria on TNT. Here we will determine if Rho0 cells were successfully engineered by labeling the mtDNA with Quant-it PicoGreen Reagent and labeling of the plasma membrane with WGA Rhodamine to determine the effects on TNT formation. We will also determine the expression levels of Myosin-X (Myo10), a known TNT inducer, in Rho0 cells versus control cells. Overall results revealed that mitochondria do play a role in TNT formation. As cells were in the process of becoming Rho0 cells, TNT formation increased peaking at week 4. As Rho0 cells stabilized, TNT formation significantly decreased. In addition, cells were seen to expel their mitochondria into the extracellular medium in week 6, a process known as mitochondrial extrusion. Lastly, Myo10 protein levels significantly increased during the production of a stable Rho0 cell line at week 4. The increase in Myo10 protein levels correlated with an increase in TNT formation.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Fresno
- Department:
- Biology
43. Partitioning the effects of habitat fragmentation on rodent species richness in Southern California
- Creator:
- Johnson, Alex M.
- Description:
- Habitat fragmentation plays a major role in species extinction and the loss of biodiversity around the globe. When fragmentation occurs, the initial loss of overall habitat alone causes species extirpation. However, species that survive this initial loss and persist in the remaining small fragments of habitat continue to experience changes that may lead to their eventual extirpation. Previous research has determined that species richness in habitat fragments is affected by a number of characteristics. These include fragment age, size, and isolation, edge effects, vegetation coverage, habitat heterogeneity, and matrix content. Although most studies focused on one or a few of these characteristics, multiple characteristics work together to affect species richness, showing that the effects of habitat fragmentation are complex. The goal of my study was to partition the complex effects of habitat fragmentation by determining the direct, indirect, and cumulative effects of multiple habitat fragment characteristics on rodent species richness. In 2013, I determined rodent species richness in 25 habitat fragments within a suburban landscape of Thousand Oaks, California. In addition, I measured the following characteristics for each fragment: fragment age, area, isolation, shrub coverage, habitat heterogeneity, perimeter/area ratio, and percent non-urban buffer. Path Analysis was used to test the hypothesized model which described the direct, indirect, and cumulative effect of each habitat fragment characteristic on rodent species richness. Habitat heterogeneity had the greatest direct and total effect on rodent species richness. In addition, fragment area had the greatest indirect effect on rodent species richness through its influence on habitat heterogeneity, suggesting that large fragments containing the greatest diversity of habitats will support the most species. Overall, the path model explained 67% of the variation in rodent species richness among habitat fragments. From a conservation and management standpoint my findings suggest that the most important fragments to protect are the largest and most habitat diverse.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Ginther, Samuel
- Description:
- The susceptibility of ecosystems to the introduction of non-native species has increased drastically with the development of advanced transportation technologies. It is now quite common for organisms to be easily transported by humans across physiological, ecological, or behavioral barriers that once served as natural population constraints. Despite this increased rate of introductions to locations that were previously unreachable, most organisms that are introduced perish because they are not able to withstand the new environmental pressures of the introduced location, or there are simply not enough conspecifics to perpetuate the population. However, when introduced organisms are able to thrive and reproduce, they may have devastating economic or ecological consequences. A new opportunity to document and understand the effects of an invasive alga on native community members has presented itself in southern Californian waters. Native to northeastern Asia, Sargassum horneri is a macroalga that was presumably transported in ballast water and discovered in Long Beach Harbor in 2003. By 2006 it had spread to the western side of Santa Catalina Island, California, and within a year spread along the entire leeward coast, forming dense stands in numerous areas. Although not all exotic species are ecologically harmful, S. horneri has attributes (fast growing and occurs in high densities) that may allow it to readily establish and outcompete marine flora critical to the community structure of fishes. The purpose of this study aimed to document the effects of S. horneri on kelp forest fishes at Santa Catalina Island, California. I first employed observational, correlative methods to explore the role of S. horneri in shaping biotic and abiotic habitat characteristics of reefs and fish assemblages. I also explored habitat characteristics that predict fish assemblage structure, as well as species-specific responses of fish to habitat predictor variables during 4 distinct time periods. Fish assemblages changed over the course of my 4 sampling periods, and a number of habitat variables (including S. horneri) explained variation in fish assemblage during those times. However, there is more evidence that favors M. pyrifera as a driver of fish assemblage change, as indicated by species-level responses. Additionally, a field experiment testing whether the removal of S. horneri from reef areas affected the fish assemblage was used to evaluate whether patterns documented in the observational portion of my study that could be attributed to S. horneri do in fact appear to be caused by the invasive alga. Removing S. horneri from established areas of reef did not affect multivariate or univariate metrics of fish assemblage over the course of 7 sampling periods. Removal and control (unaltered) areas of reef contained strikingly similar fish assemblages, fish richness, and fish densities over time. Despite a drastic change in reef landscape, it appears that M. pyrifera, rather than S. horneri, was a more significant driver of differences in kelp forest fish assemblages observed in my study. Second, I compared the role of relatively low-lying S. horneri and vertically extensive M. pyrifera in shaping recruitment patterns of a popular sport fish (Paralabrax clathratus) by using an observational and experimental study. I first examined kelp bass recruit abundance on naturally standing S. horneri and M. pyrfera to better understand how fish recruitment rates differ between the introduced and native species. Additionally, I experimentally isolated 3 treatments (M. pyrifera only, S. horneri only, and M. pyrifera and S. horneri together) over a sandy bottom to understand whether the presence of S. horneri, and increased benthic complexity for young fish, enhances kelp bass recruitment. An overwhelming majority of kelp bass recruited to M. pyrifera, and larger recruits were located in the bottom two-thirds of the thalli. Kelp bass recruitment was were observed with S. horneri, regardless of whether the alga was alone or paired with M. pyrifera. Similar to my observational results, larger kelp bass recruits were observed in the bottom third of M. pyrifera treatments. Additionally, I found that that the presence of larger, predatory conspecifics explained a spatial pattern of declining recruitment rates across treatment plots. My study presents the first evidence that S. horneri negatively impacts the recruitment of an important southern California reef fish. Results from both of my studies offer contrasting outlooks on S. horneri's role in southern California kelp forests. When focusing on the entire fish assemblage, little evidence is in favor of S. horneri as a driver of kelp forest fish structure. However when focusing on a particular early life history characteristic of a common kelp forest fish, the effects of S. horneri are dramatically negative. The contrasting results of my studies are important reminders for the need of additional studies to generate a more comprehensive understanding of this invasive alga's impact on kelp forest organisms.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Parker, Jeffrey Thomas
- Description:
- The purpose of this study is to compare the genetic distances of Mimetus hesperus and Theridion neomexicanum within and between the San Joaquin Valley and Mojave Valley regions. To my best knowledge this is the first genetic study of M. hesperus. Mountains and distance are well known barriers to gene flow in species with lower vagility. For short lived spiders, the only non-synanthropic transport method over mountains is ballooning. Ballooning spiders rely on surface area for lift, and larger spiders have a difficult time sustaining flight as they have less surface area per unit weight. M. hesperus hunts other spiders and probably has large spiderlings which make it difficult to balloon from hatching. With insufficient ballooning the Sierra Nevada Mountains should act as a barrier to gene flow for M. hesperus. I predict that comparisons between populations of M. hesperus on the same side of the Sierra Nevada Mountains will show smaller genetic distances than comparisons between populations on opposite sides of the mountains. M. hesperus and T. neomexicanum were collected from sites around the Sierra Nevada Noubtains and either died of natural causes or were humanely euthanized in <0°C ethanol. DNA was extracted and PCR was run to amplify the cytochrome oxidase 1 sununit c gene. Amplified sequences were run in two percent agaorse gel to look for banding of appropriate length and gels showing target band were purified and sent to the University of Florida for sequencing. All other bands were heavily troubleshooted and re amplified Sequence chromatograms were analyzed to ensure only pure sequences were used in analysis. Insufficient numbers of T. neomexicanum were resolved so they were used as outgroups in analyzing M. hesperus. Sequences were aligned using clustalW and cut in MEGA to ensure accurate comparisons. Pairwise distances were calculated between all specimens. A neighbor joining tree was calculated, and overall percent divergence based on collection sites, and tree groupings was computed. Character based maximum parsimony and maximum likelihood trees were calculated to confirm results seen in neighbor joining analysis. Haplotype diversity was shown by grouping all single nucleotide polymorphisms for comparison of haplotypes and by collection site and tree groupings. Genetic distance and trees reveal three distinct groupings of M. hesperus, but a permutation test found distance within populatioins from both sides insignificant, so all specimens were grouped as either east or west of the mountains. Although anecdotal at best, haplotype diversity hints that M. hesperus may have brached from the west to the east. The Sierra Nevada Mountains appear to separate populations of M. hesperus in the Central Valley and in the Mojave more than distance alone. M. hesperus populations collected over 100 miles apart on the west side of the mountains showed no significant divergence, indicating some unknown mechanism of gene flow linking these populations, but a larger sample size is needed to confirm this.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Kolan, David Martin
- Description:
- In sea urchin eggs the hexose monophosphate shunt is the main glycolytic pathway before and after fertilization, and glucose-6-phosphate dehydrogenase (G6PD) is the main regulatory enzyme of the pathway. Activity of the enzyme increases with fertilization, thought to occur as a result of activation of NAD kinase and glycogen phosphorylase and simultaneously increased titers of NADP and glucose-6-phosphate (G6P). Part of the enzyme activity is associated with the egg surface membrane complex. Experiments have been done to determine the effects of extraction pH upon isozymes in unfertilized eggs, and what effects dithiothreitol (DTT, a sulfhydrl reducer), papain (a well known thiol protease), NADP, NAD, G6P, and other substrates have when added exogenously, upon the formation of isozymes and the mechanics of isozyme change as a part of the program of fertilization. Control extracts of pellet and gel fractions of unfertilized egg homogenates of the species Strongylocentrotus purpuratus show three isozyme bands when extracted using 0.01M MgCl2; these bands are designated B1, B2, and B3, the slowest to fastest migrating respectively with electrophoresis. Extraction with Lubrol WX yields an even slower moving band, BL. Fertilized eggs are shown to lack a B3 band. Extraction pH has been found to have no effect upon formation of isozymes between pH 6.4 and 7.9, whether pellet or gel extract. Unfertilized and fertilized egg pH 7.9 extracts with DTT added show the apparent extinction of activity of all but the B2 isozyme band, thought to be due to sulfhydryl inhibition of the binding of NADP to cysteine residues of the G6PD isozymes inactivated by DTT. Papain added to unfertilized egg extracts has no visible effect upon the isozymes, while fertilized egg extracts take on somewhat the appearance of unfertilized eggs, gaining the B3 band and partially losing B1, indicating a relationship between B1 and B3. Addition of NADP and G6P together causes the apparent disappearance of the B3 isozyme in unfertilized egg extracts and slightly increased mobility in both fertilized and unfertilized cases. With the experimental results in mind, it is proposed that increased NADP titers cause a release of lower molecular weight isozymes from membranes to soluble phases of the cell, and increased concentrations of substrate and specific cofactor complete formation of a larger G6PD isozyme, with the greater enzyme activity available to supply the energy for the metabolism of the newly formed sea urchin zygote.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Hult, Susan Marie
- Description:
- The Blainville's Horned Lizard (Phrynosoma blainvillii) is endemic to California and ranges from northern California (Butte County), to the northwestern tip of Baja California in the southern part of its range, west of the Sierra Nevada Mountains and the southern California deserts in the eastern part of its range, and along the Pacific coast from northern Baja California to Monterey, California in the western part of its range. Phrynosoma blainvillii is listed as a California Species of Special Concern and a Bureau of Land Management (BLM) Sensitive Species. Human activities have been primarily responsible for declines in populations. There has been few field research studies published on the general ecology of P. blainvillii, particularly in the San Joaquin Valley. I initiated a radio-telemetry study to collect data on home range size and habitat use at two sites (Atwell Island and Semitropic Ridge Preserve) in the southern San Joaquin Valley, California. I calculated home range size from 10 lizards, five at each site. Using the 100% Minimum Convex Polygon (MCP) estimator I found home range sizes were between 0.58 ha to 13.93 ha, with an average size of 4.98 ha (± 1.54). When above ground and active, P. blainvillii at either site used areas of bare ground more often than expected based on equal use. At the Semitropic site, the lizards used areas under shrubs almost as often as bare ground, while at the Atwell site the lizards used areas of sparse vegetation more often than expected, but not as much as bare ground. Lizards at both sites used medium-dense and dense areas of vegetation much less than expected based on equal use. In adult P. blainvillii, we recorded a moderately skewed sex ratio of more males than females, but in young P. blainvillii, there were more females than males. Average snout-vent length (SVL) of females was 72.31 mm and for males 68.81 mm. The adult horned lizards were most active in April and May while young horned lizards were most active in August and September. In the spring, the morning activity hours peaked at 0900–1100, in summer, it was 0900–1000, and in fall, it was 0900–1300. All age classes of P. blainvillii were most often above ground and active at surface temperatures of 28–34°C. The presence of alkali flats and sandy soil correlated with a high abundance of horned lizards, and within our two study locations, they revealed a distinct preference for Sandridge loamy fine sand over other available soil types. The lizards used kangaroo rat burrows rather than shrubs for heat refugia but used shrubs frequently as an escape from predators. Food items found in scats were predominantly ants, but beetles and other arthropods were also found in large numbers.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Bakersfield
- Department:
- Biology
- Creator:
- Jones, Maureen Gertrude
- Description:
- In most temperate coniferous forests, the vast majority of vascular plant species richness can be found in the understory layer. While the large-scale conversion of forests to plantations has made it increasingly important to understand how understory flora responds to timber harvesting, there is a surprising paucity of data concerning this topic. Ideally, long-term studies using permanent plots would be used to directly assess post-logging patterns of recovery, both for whole floras and for individual species of conservation interest. Unfortunately, these studies are lacking, and alternative approaches are critical. I used a 420 year forest chronosequence to assess the relationship between stand age, overstory cover and vascular plant understory richness and composition in one watershed in the Siskiyou Mountains of Oregon. The chronosequence consisted of six young managed (age 7-44) and nine older unmanaged (age 90-427) stands. All stands were similar in underlying geology, slope, elevation, and aspect. I found a non-linear relationship between stand age and richness, in which richness showed a steady decline as young stands entered canopy closure, then increased as stands gained older forest attributes such as light gaps and structural diversity. I also found that percent open canopy was correlated with total percent understory cover, richness, diversity and changes in species composition. In general, young stands were characterized by high shrub and graminoid cover and old stands were characterized by an abundant herb layer. In my study area, a large proportion of young managed stands are currently entering canopy closure, a stage characterized by low vascular plant species richness and abundance. I use my results to discuss the potential effects of past and future forest management on vascular plant understory species.
- Resource Type:
- Masters Thesis
- Campus Tesim:
- Humboldt
- Department:
- Biology
- Creator:
- Pucci, Jolene R.
- Description:
- Invasive plants threaten native biodiversity and ecosystem function. Non-native plants can out-compete native plants for resources, reducing population sizes. For rare species, this can increase the chances of extinction. Pentachaeta lyonii is an endangered, endemic sunflower, currently ranging entirely within the urbanized Santa Monica Mountains and Simi Hills. Its former range and number of populations have been reduced in recent decades due to pressures from urbanization, and the remaining populations are in decline. This study examined the effects of competition from invasive plants as a possible cause of declines by evaluating both effects from competition and effects from community alteration. Three invasive plant groups (annual grasses, Erodium spp., and Centaurea melitensis) were studied in (1) direct competition experiments in the field and in pots, (2) observational studies comparing sites where P. lyonii is extant and extirpated, and (3) manipulative community-level experiments. In the field and pot competition experiments, all three invasive groups competitively reduced the reproductive capacity of P. lyonii, and had differing effects on P. lyonii height. Observational studies showed that the presence of annual grasses and its associated litter were correlated with extirpation, and retention of bare ground was correlated with P. lyonii persistence. Restoring P. lyonii habitat to pre-invasion conditions by removing non-native plants, scraping the soil surface, and adding cryptobiotic crust increased native species richness and reduced the cover of annual grasses. Seeding P. lyonii increased its density in existing sites, and was successful in establishing plants in new sites. Removal of invasive plants and their associated litter in P. lyonii habitat, and seeding existing and new populations are recommended for restoration and recovery of the species.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology
- Creator:
- Schmidt, Susan Yolande
- Description:
- The growth in length and weight of immature fruit and seed of carob (Caratonia siliqua L.) was studied over a period of seven months. During the early periods of development, seed and fruit growth follow a parallel course; however, the seed continue to grow even after the fruit growth has ended. The embryo and endosperm grow at a faster rate than the seed coat during this later phase of growth. Extracts for growth inhibitors were also made from the developing fruit. All the extracts were significantly inhibitory in the pea bioassay at concentrations of extract from 0.5 mg FW/plant. During the last two months of growth prior to desiccation quantitative extractions of inhibitor from the seed coat, endosperm and embryo were made. At least 92% of the inhibitor in the seed is concentrated in the seed coat. The whole extract and one partially purified fraction, C, were studied for the effect of germination of ripe carob seed. They were found to delay germination, inhibit the growth of the germinating seed, and to decrease the amount of reducing sugar in the medium of the germinating seed. It is inferred that the inhibitor imposes a block to either the synthesis or the release of enzyme(s) involved in the breakdown of the reserve galactomannnan.
- Resource Type:
- Thesis
- Campus Tesim:
- Northridge
- Department:
- Biology