Life Sciences Commons^™

Anatomical Analysis Of Somatic Mutation Accumulation In Mimulus Guttatus, Amanda Burrell

University Honors Theses

Plants are seemingly immortal in their abilities to survive long periods of dormancy in different life stages, live for thousands of years, and even grow into whole forests from one clone, all through a series of mitotic and meiotic events, but how many mutations do plants acquire in their lifetime? And just how many of these mutations are heritable? To answer these questions, first we must answer: how many cell divisions are there in the length of a stem? The purpose of this study is to answer just that by establishing a protocol for estimating the number of germ cell …

Do Fungal Symbionts Of Salt Marsh Plants Affect Interspecies Competition?, Vanessa Robertson-Rojas

Dissertations and Theses

The effects of arbuscular mycorrhizal fungi (AMF) as salt marsh plant symbionts may have significant effects on landscape scale distribution patterns and plant-related ecosystem functions that are important to estuarine habitats. This work investigates the effects AMF have on Phalaris arundinacea, Deschampsia cespitosa, and Juncus balticus when grown in a common garden experiment. Plants were grown with and without AMF inoculation in both polyculture and monoculture communities and examined for a variety of response variables that represent different competition strategies. Factorial ANOVA analysis revealed a significant three-way interaction among fungal treatment type, community type, and species for …

Recurrent Formation, Low Levels Of Ecological Differentiation, And Secondary Dispersal Facilitate The Establishment And Persistence Of Autopolyploids In Eriophyllum Lanatum, Nicolas Alexander Diaz

Dissertations and Theses

The high rates of polyploidization events in angiosperms is a well-documented driver of diversification and speciation. The consequences of polyploidy--from gene expression up to ecology--and the processes facilitating the persistence of polyploidy in its early establishment in populations are poorly understood. In this thesis, I examined the role of recurrent formation, ecological differentiation, and secondary dispersal via biotic vectors in the maintenance and persistence of an intervarietal polyploid contact zone of Eriophyllum lanatum in Southern Oregon. Sampling 35 total populations, I used a whole chloroplast capture and flow cytometry to determine the diversity and distribution of chloroplast haplotypes and estimate …

Genetic Diversity Correlates With Morphological Diversity Among Populations Of Achyrachaena Mollis, Rachel S. Bice

University Honors Theses

Biodiversity is important for ecosystem health and sustainability, especially in the current, rapidly changing climate. Understanding the underlying causes behind morphological variation will allow for more accurate predictions about how a population will respond to climate change, and potentially yield better natural resource management strategies. Achyrachaena mollis is an annual, self-fertilizing, range-limited, endemic species found in Northern California and Southern Oregon. This species depends primarily on wind seed dispersal for gene flow, making it a good study species in seed dispersal experiments. Additionally, A. mollis is more readily influenced by changes in its environment than a perennial due to its …

Impact Of The Urban Heat Mosaic On The Leaf Senescence In Two Acer Species, Jeffrey D. Smith

University Honors Theses

Due to the heterogeneity of the urban heat island, we can think of the variable influence of urbanization on air temperature as more of an urban heat mosaic. Climate change has caused a resurgence of interest in the way temperature affects how organisms, such as street trees, undergo cyclic changes in their life cycle. Such changes include budburst or, less commonly, timing of senescence. Little is known about how the urban heat mosaic could be affecting the phenology of different urban trees. Because street trees are one of the more prominent ecosystem engineers of the urban landscape, variable influences of …

Isoprene Emission In Polytrichaceae Mosses, Timea Deakova

Dissertations and Theses

Our first aim was to identify and quantify Biological Volatile Organic Compound (BVOC) emissions, specifically emissions of isoprene, from the moss Polytrichum juniperinum during its earliest stage of life. Isoprene emission from mosses could be a significant component of the total global budget of BVOC emissions. Data concerning the spatial and temporal variability of these emissions are lacking due to poor characterization of the physical and biological factors controlling isoprene synthesis in both vascular and non-vascular plants. We found that P. juniperinum in its early life stage (protonema) can emit isoprene at detectable levels at day five after spore germination. …

Composition And Dispersal Dynamics Of Vegetation Communities In Urban Riparian Forests, Christa Von Behren

Dissertations and Theses

In urban riparian areas, vegetation composition may be affected by urban land use changes at both the stream reach and the watershed scale. Moreover, the mechanisms by which seeds disperse may be affected both by reduction in seed sources due to vegetation removal and by the urban stream syndrome that produces flashier hydrographs and incised channels. I hypothesized that vegetation communities with high cover of native and hydrophilic species would be found in watersheds with high forest cover, while more limited cover of these species would be found in highly developed watersheds. Additionally, to examine the dispersal mechanisms contributing to …

Effect Of Microbes On The Growth And Physiology Of The Dioecious Moss, Ceratodon Purpureus, Caitlin Ann Maraist

Dissertations and Theses

The microorganisms colonizing plants can have a significant effect on host phenotype, mediating such processes as pathogen resistance, stress tolerance, nutrient acquisition, growth, and reproduction. Research regarding plant-microbe interactions has focused almost exclusively on vascular plants, and we know comparatively little about how bryophytes -- including mosses, liverworts, and hornworts -- are influenced by their microbiomes. Ceratodon purpureus is a dioecious, cosmopolitan moss species that exhibits sex-specific fungal communities, yet we do not know whether these microbes have a differential effect on the growth and physiology of male and female genotypes. Using a common-garden design, we reared ten axenic genotypes …

Urban Impacts To Forest Productivity, Soil Quality, And Canopy Structure In Forest Park, Portland, Oregon, Andrew David Addessi

Dissertations and Theses

Land use practices and exposure to low impact disturbances associated with an urban environment can alter forest structure and function. Past and ongoing research in Forest Park, a large urban forest in Portland, Oregon, suggests that mature mixed Douglas-fir (Psuedotsuga meziesii)-hardwood stands in the more urban end of the park lack a shade-tolerant conifer understory composed of the late successional conifer tree species, such western hemlock (Tsuga heterophylla) and western red-cedar (Thuja plicata). 5-year plot remeasurement data that characterizes productivity and mortality patterns did not show a strong relationship to urban proximity. Plot productivity …

Symbiosis With Nitrogen-Fixing Rhizobia Influences Plant Defense Strategy And Plant-Predator Interactions, Adrienne Louise Godschalx

Dissertations and Theses

As sessile organisms, plants evolved a plethora of defenses against their attackers. Given the role of plants as a primary food source for many organisms, plant defense has important implications for community ecology. Surprisingly, despite the potential to alter entire food webs and communities, the factors determining plant investment in defense are not well-understood, and are even less understood considering the numerous symbiotic interactions in the same plant. Legume-rhizobia symbioses engineer ecosystems by fixing nitrogen from the atmosphere in trade for plant photosynthates, yet connecting symbiotic resource exchange to food web interactions has yet to be established. Here I test …

Ecosystem Recovery In Estuarine Wetlands Of The Columbia River Estuary, Sarah Ann Kidd

Dissertations and Theses

In the restoration of tidal wetland ecosystems, potential drivers of plant community development range from biotic controls (e.g. plant competition, seed dispersal) to abiotic controls (e.g. tidal flooding, salinity levels). How these controls influence the success of tidal wetland restoration are only partly understood, but have important implications for wetland habitat recovery. Specifically, the extent to which the existing native and non-native seed banks in tidally reconnected wetlands interact with these controls is not clear, yet the potential success of passive restoration methods depends upon this understanding.

For a 54-year chronosequence of eleven tidal wetland restoration sites in the Lower …

An Efficient Pipeline For Assaying Whole-Genome Plastid Variation For Population Genetics And Phylogeography, Brendan F. Kohrn

Dissertations and Theses

Tracking seed dispersal using traditional, direct measurement approaches is difficult and generally underestimates dispersal distances. Variation in chloroplast haplotypes (cpDNA) offers a way to trace past seed dispersal and to make inferences about factors contributing to present patterns of dispersal. Although cpDNA generally has low levels of intraspecific variation, this can be overcome by assaying the whole chloroplast genome. Whole-genome sequencing is more expensive, but resources can be conserved by pooling samples. Unfortunately, haplotype associations among SNPs are lost in pooled samples and treating SNP frequencies as independent estimates of variation provides biased estimates of genetic distance. I have developed …

Let The Seeds Fall Where They May: Investigating The Effect Of Landscape Features On Fine-Scale Seed Dispersal, Monica R. Grasty

Dissertations and Theses

Seed dispersal is a crucial ecological and evolutionary process that allows plants to colonize sites and expand their ranges, while also reducing inbreeding depression and facilitating the spread of adaptive genetic variation. However, our fundamental understanding of seed dispersal is limited due to the difficulty of directly observing dispersal events. In recent years, genetic marker methods have furthered our understanding of colonization and range expansion due to seed dispersal. Most investigations focus on regional scales of dispersal, due to low levels of variation in the chloroplast genome (cpDNA), which can serve as an indirect measure of seed dispersal. Here, I …

Sex-Specific Fungal Communities Of The Dioicous Moss Ceratodon Purpureus, Mehmet Ali Balkan

Dissertations and Theses

Mosses display a number of hallmark life history traits that influence their ecology at the population and community level. The long lived separation of sexes observed in the haploid gametophyte (dioicy) is one such feature of particular importance, as it is observed in the majority of bryophytes and creates intraspecific specialization of male and female individuals.

The prevalence of sexually dimorphic mosses raises the possibility of sex-specific interactions with fungi as observed in some vascular plants. Here I investigated how moss sex shapes fungal communities associated with gametophytic tissues of the ubiquitous moss, Ceratodon purpureus. Using greenhouse populations of …

Assessment Of Arbuscular Mycorrhizal Symbiosis On Invasion Success In Brachypodium Sylvaticum, Caitlin Elyse Lee

Dissertations and Theses

The effects that mutualistic soil biota have on invasive species success is a growing topic of inquiry. Studies of the interactions between invasive plants and arbuscular mycorrhizal fungi (AMF) have shown changes in AMF community composition, reductions in AMF associations in invasive plants, and changes in native species fitness and competitive outcomes in invasive-shifted AMF communities. These findings support the degraded mutualist hypothesis, where invasive species alter the mutualist community composition, resulting in detrimental associations with the new mutualist community for native species. Here I present two studies that examine various aspects of the arbuscular mycorrhizal fungal (AMF) mutualism in …

Testing The Ecological And Physiological Factors Influencing Reproductive Success In Mosses, Erin Elizabeth Shortlidge

Dissertations and Theses

As non-vascular, early land plants with an aquatic ancestry, mosses do not regulate internal water conditions separate from that of their environment and as a result, evolved mechanisms to survive in a terrestrial world out of water. Yet, there is a widely accepted dogma that moss reproductive success is solely dependent on rainfall events carrying swimming, bi-flagellate sperm across the landscape to reproductively mature and receptive female mosses--but this classic view of moss reproduction may be too simplistic. In this dissertation I test the assumptions of reproductive limitation in mosses and present novel findings in a basal, yet understudied terrestrial …

Agricultural Management Decisions Impact Isoprene Emission And Physiology Of Arundo Donax, An Emerging Bioenergy Crop, Jason Charles Maxfield

Dissertations and Theses

Arundo donax (Giant Reed) is quickly being developed as a rapidly-growing, robust, and highly productive bioenergy crop, with large scale cultivation of this species planned for the Columbia River basin of the Pacific Northwest (USA). Despite its potential as a next generation biomass crop, relatively few studies have examined the physiological performance of A. donax under agricultural conditions. Unlike traditional crops, A. donax is known to be a high-emitter of the volatile compound isoprene, which may significantly impact regional air quality, but it has not been widely cultivated in North America and little is known about how this species will …

Effects Of Arbuscular Mycorrhizal Fungal Infection And Common Mycelial Network Formation On Invasive Plant Competition, Rachael Elizabeth Workman

Dissertations and Theses

Understanding the biotic factors influencing invasive plant performance is essential for managing invaded land and preventing further exotic establishment and spread. I studied how competition between both conspecifics and native co-habitants and arbuscular mycorrhizal fungal (AMF) impacted the success of the invasive bunchgrass Brachypodium sylvaticumin early growth stages. I examined whether invasive plants performed and competed differently when grown in soil containing AMF from adjacent invaded and noninvaded ranges in order to determine the contribution of AMF to both monoculture stability and spread of the invasive to noninvaded territory. I also directly manipulated common mycelial network (CMN) formation by AMF …

Interspecific Variation In Leaf-Level Biogenic Emissions Of The Bambuseae, Andrea Natalie Melnychenko

Dissertations and Theses

Plants emit a diverse range of biogenic volatile organic compounds (BVOCs) into the atmosphere, of which isoprene is the most abundantly emitted. Isoprene significantly affects biological and atmospheric processes, but the range of isoprene and BVOCs present in bamboos has not been well characterized. In this thesis I explore the range of isoprene emission found in bamboos and relate it to plant morphological and physiological characteristics. In addition, I measure and relate the entire suite of BVOCs present in the bamboos to their fundamental isoprene emission rate.

Interspecific variation in isoprene emission documented in a comprehensive survey of bamboos. Two …

Effects Of Increased Nitrogen Deposition On The Dominance Of Hedera Helix In The Pacific Northwest, Bianca Christine Dolan

Dissertations and Theses

Increased nitrogen deposition has been shown to promote the dominance of invasive species, and nitrogen deposition rates have steadily increased in most of the Western United States in recent years due to population increases. The purpose of this study was to determine if increased rates of nitrogen deposition are contributing to the success of Hedera helix in the Pacific Northwest. Plots were established in Lesser Park in Portland, Oregon and received monthly treatments of ammonium nitrate for one year. Growth, measured as change in percent cover, was compared between treated and untreated plots for both H. helix and native species. …

First Bacterial Endosymbionts Found In The Phylum Ascomycota, Eileen Elizabeth Fitzpatrick

Dissertations and Theses

Organisms belonging to the Kingdom Fungi are known to occupy a wide variety of ecological niches and are found globally in virtually all environments. Two members of the smallest of the fungal phylum, the Zygomycota, have also been found to harbor intercellular bacteria initially described as being from or closely related to organisms from the Genus Burkholderia. In this study two microaerophilic members of the species Verticilium from the phyla Ascomycota were characterized. Both appear to carry two bacterial endosymbionts. This is the first evidence of bacterial endosymbionts found within a member of the Ascomycota. Through the use of fluorescent …

Effects Of Reactive Oxygen Species On Life History Traits Of Caenorhabditis Elegans, Samson William Smith

Dissertations and Theses

Evolutionary life history theory predicts that tradeoffs among fitness-related phenotypes will occur as a result of resource limitations and/or physiological constraints. Such tradeoffs are defined as the cost(s) incurred on one component of fitness (e.g., reproduction) by the increased expression of another fitness-related trait (e.g., longevity). Only recently have researchers begun to investigate the mechanistic bases of life history tradeoffs. A recent proposal is that reactive oxygen species (ROS) have a central role in shaping life history traits and tradeoffs. Research on disparate animal taxa has highlighted strong correlations between oxidative stress resistance and fitness-related life history traits, for example. …

Biological Control Of Purple Loosestrife (Lythrum Salicaria): Factors Affecting Galerucella Pusilla And Galerucella Calmariensis Establishment In Tidal Areas, Lynda Kathryn Moore

Dissertations and Theses

Galerucella pusilla and G. calmariensis have provided successful biological control of purple loosestrife (Lythrum salicaria L.) in non-tidal areas but only marginal control in areas of tidal influence. While a previous study identified mechanical scour by tidal waters as the main cause of establishment failure, purple loosestrife stem density explained more than 80% of the variability in presence and absence of Galerucella at my study sites in the Columbia River Estuary. A logistic regression model using purple loosestrife stem density, elevation, and their interaction as predictors accurately predicted 92.5% of Galerucella presence or absence observations of a test data …

Effects Of Surrounding Land Use On Plant Species Composition In Urban Forest Fragments, Bruce Michael Barbarasch

Dissertations and Theses

As human development occurs in forested areas, forests become fragmented into small islands in a matrix of urban land uses. This study examined the effect of surrounding urban land uses on the native and exotic plant species found on the edges of forest fragments in the Portland, OR metropolitan region.

The Effect Of Plant Growth Regulators On The Growth Of Closterium Moniliferum, Cynthia Lehua Warnock Christensen

Dissertations and Theses

Physiologic responses to Gibberellic Acid (GA), 1-Naphthalene Acetic Acid (NAA), Benzylaminopurine (BAP), and Abscisic Acid (ABA), suggest that Closterium moniliferum has the ability to utilize these plant growth factors. The growth promoters NAA and GA both increased growth when added to the media. The cell division regulator BAP (a synthetic cytokinin). also had a promotive effect on growth. Abscisic acid was found to be inhibitive to growth.

Double Cross: Agriculture And Genetics, 1930 To 1960, Tracy Scott Lebenzon

Dissertations and Theses

This paper discusses the role of genetic technology and application in agriculture between 1930 and 1960. Topics covered include the role of genetics and the relationship that theory, education, administration, professionalism, economic and social considerations bore to genetics.

The Role Of Iron Nutrition In Regulating Patterns Of Photosynthesis And Nitrogen Metabolism In The Green Alga Scenedesmus Quadricauda, Dennis Raymond Ades

Dissertations and Theses

The influence of iron nutrition on patterns of photosynthetic behavior, nitrogen metabolism, and fixed-carbon allocation is reported for a common freshwater green alga. Cultures of Scenedesmus quadricauda were grown in Fraquil medium in which iron concentrations ranged from 1.0 μM to 0.01 μM (log 10-6 to 10-8 M, respectively). Carbon 14 and nitrogen uptake experiments were conducted at photosynthetically saturating and subsaturating photon flux densities.