Biology Commons^™

Coexistence Of Sympatric Taxa Of Chamaecrista Section Xerocalyx: Addressing The Interplay Between Morphology And Biotic Interactions, Beatriz Baker-Méio

Dissertations

Animal-plant interactions may prevent gene flow and promote divergent selection among closely related plants, ultimately leading to formation of new species. This may be the case for Chamaecrista sect. Xerocalyx, in which two or more of the 24 varieties often are encountered in the same area, with marked morphological and phenological differences among them. Over a broad geographical range, however, the morphological gaps among varieties disappear. Several biotic interactions contribute to the fitness of Chamaecrista species. Their flowers are pollinated by bees, and herbivores attack their leaves, flowers, fruits, and seeds. In addition, all species produce extrafloral nectar, which …

Marine Fungi Of U.S. Gulf Of Mexico Barrier Island Beaches: Biodiversity And Sampling Strategy, Allison Kathleen Walker

Dissertations

Marine fungi are an important but often overlooked component of marine ecosystems. Primarily saprotrophic, they are vital to coastal nutrient cycling processes and food webs. However, basic marine fungal distribution data are lacking in many parts of the world, as is knowledge of the sampling intensity required to characterize the biodiversity of these communities. The roles of substrate, season and latitude in shaping intertidal ascomycete community structure were examined for the U.S. Gulf of Mexico, and the role of sampling frequency on species richness estimates was also addressed. Best sampling practices were developed and 750 collections of beach detritus, sand …

Management Of Biological And Chemical Constituents For The Advancement Of Intensive, Minimal-Exchange, Biofloc-Based Shrimp (Litopenaeus Vannamei) Aquaculture, Andrew James Ray

Dissertations

Intensive, minimal-exchange, biofloc-based shrimp aquaculture systems may provide a sustainable alternative to traditional shrimp culture. Through a series of experiments, this document explores the effects of several key management strategies on water quality, isotopic distribution, and shrimp production.

An experiment evaluated the effects of managing suspended solids (biofloc) concentration at two levels. It was found that using a higher flow rate to larger settling chambers resulted in significantly lower biofloc and nitrate concentrations, and significantly improved shrimp growth rate. A second experiment compared systems with clear water and systems with biofloc. The filters in the clear water systems prevented biofloc …

A Time Series Analysis Method Using Hidden Variables For Gene Network Reconstruction, Xi Wu

Dissertations

The DNA microarray technology can be applied to obtain time series data which contains thousands of genes and tens of time points. When confront the great amount of data points a fast and effective method must be constructed to extract useful information. The assumption that the interactions between genes are static in the time series data is made. After made the assumption how to reconstruct those interactions becomes a difficulty problem. Since the underlying interactions between genes are complicated, which involve transcription, translation and protein-protein interaction, to construct a model from physicochemistry is almost impossible/effortless. The popular methods constructed from …

The Role Of The Cysteine/Glutathione Regulatory Genes Cdo1, Gsh1, And Gsh2 In Yeast-Mold Dimorphism Of The Pathogenic Fungus Histoplasma Capsulatum, Melissa Anne Adams

Dissertations

The dimorphism of Histoplasma capsulatum (Hc) from a mold to yeast is regulated by many environmental factors such as temperature and thiol concentrations. Histoplasma exists in the soil (or in vitro at 25ºC) as a multicellular saprophytic mold. In the lungs of an infected host (or in vitro at 37ºC), a shift to the unicellular parasitic yeast occurs. Sulfhydryl groups (-SH), especially cysteine, are necessary in the culture medium for the mold to yeast transition. Cysteine is the precursor for the synthesis of glutathione. Enzymes involved in the cysteine metabolism pathway are being studied in order to evaluate …

Urban Development In Costa Rica: The Direct And Indirect Impacts On Local And Regional Avian Assemblages, Jeff L. Norris

Dissertations

Urban development, the pinnacle of human land use, has drastic effects on native ecosystems and the species they contain. For the first time in recorded history there are more people living in cities than in the rural areas surrounding them. Furthermore, the global rate of urbanization continues increasing; raising serious concerns for earth's tropical regions as they harbor a disproportionate amount of the earth's species, and where the impacts of urban development on natural communities are poorly known. Therefore, for my dissertation research I investigated the impacts of urban development on avian community structure and organization at both local and …

The Effect Of Photoperiod On Regulation Of Key Components Of The Life Cycle In The Bumble Bee Bombus Impatiens L. (Hymenoptera: Apidae)., Edgar Javier Hernandez

Dissertations

This study investigates how photoperiod affects internal characteristics of colonies of the temperate bumble bee Bombus impatiens particularly; development, reproduction, and social behavior. To answer this question I used an experimental approach using commercially obtained colonies of B. impatiens kept under controlled environmental conditions, and using the exposure to photoperiod as the only variable. Eight different photoperiod treatments were evaluated over the social phase of the colony’s life cycle. Colonies exposed to photoperiods that simulate the species natural temperate photoperiod exhibited larger growth rates, higher, oviposition rates, and higher brood survival than colonies exposed to constant photoperiods. Similarly, colonies exposed …

Host-Parasite Interactions In Galapagos Seabirds, Iris Ilena Levin

Dissertations

Parasites exhibit a wide range of life history strategies that contribute to different dispersal abilities, host specialization, transmission modes, life-cycle complexity and population structure. Understanding dispersal rates in hosts and parasites is instrumental in defining the scale at which coevolution may be occurring. In order to better understand how and when parasites move between different hosts, I studied a seabird – Hippoboscid fly ectoparasite (and vector) – Haemosporidian parasite system in the Galapagos Islands. I began by describing the Haemosporidian parasites of Galapagos seabirds, discovering a Plasmodium species parasite in Galapagos Penguins (Sphensicus mendiculus), and a new clade of Hippoboscid-vectored …

Evolution And Biogeography Of Fire-Eye Antbirds (Genus Pyriglena): Insights From Molecules And Songs, Marcos Maldonado Coelho

Dissertations

The importance of climatic and geologic factors as drivers of population differentiation and speciation in the Neotropical region has long been appreciated. However, many questions remain regarding their roles underlying the processes and patterns of diversification. Studies conducted in distinct regions containing a suite of geological and ecological conditions constitute ideal scenarios to assess the role of Pleistocene climatic changes, rivers, and mountain building as historical diversification mechanisms. In chapters 1 and 2, I used an integrative approach combining molecular phylogenetics, phylogeography and population genetics to elucidate the importance of climatic and geological factors as engines of diversification. I focused …

Clam (Corbicula Fluminea) As A Potential Sentinel Of Human Norovirus Contamination In Freshwater, Xunyan Ye

Dissertations

The purpose of this study was to evaluate and validate the use of the clam Corbicula fluminea as a sentinel of human noroviruses (HuNoV) contamination in freshwater. The first specific aim was to develop a new method to extract HuNoV RNA from contaminated bivalves (e.g. oysters, clams) that would be much faster than existing methods. The procedure developed includes an initial total RNA extraction using TRI Reagent, followed by HuNoV RNA concentration and purification using biotinylated probe-capture technology. HuNoV RNA is finally detected by real-time RT-PCR. Using bivalve homogenates spiked with HuNoV, 100 PCR detection units of the virus was …

Genetic Variation In Potentially Virulent Vibrio Parahaemolyticus From The Northern Gulf Of Mexico, Nicholas Felix Noriea Iii

Dissertations

Vibrio parahaemolyticus (V_p) is a gram-negative bacterium found naturally in marine and estuarine environments. V_p is found in oysters including those which are later consumed by the public. Sub-populations of potentially virulent Vp contain specific virulence factors and are relevant human pathogens capable of causing gastroenteritis, wound infection, and death. The tdh and trh genes, both encoding hemolysins, have been correlated with the majority of clinical V_p isolates but have not been shown to be the definitive virulence factors.

A total of 146 V_p isolates from the northern Gulf of Mexico were collected and probed …

Application Of A Hybrid 3d-Var Data Assimilation System In The Monterey Bay To Study Regional Dynamics Of The California Current System, Chudong Pan

Dissertations

A data assimilation system combining 3-dimensional variational scheme and Navy Coastal Ocean Model was applied to the Monterey Bay area to assimilate temperature and salinity glider data collected in August 2003. The hybrid background error covariance model in the present 3-dimensional variational system incorporates both the static and the flow-dependent background error covariance. To explore the impact of high temporal resolution on the overall skill of the assimilation system, the intended data assimilation interval was set to 1 hour in the present study. A Floating Temporal Window approach is designed to keep the computational efficiency of the scheme and to …

Analysis Of The Condition-Specific Regulation Of Puf3p Activity And Puf3p-Mediated Translational Repression Of Mrna In Saccharomyces Cerevisiae, Melanie A. Miller

Dissertations

The Puf family of proteins regulates aspects of eukaryotic development such as embryonic development, and memory formation by promoting translational repression and/or degradation of targeted mRNAs in the cytoplasm. Yeast Puf3p regulates mitochondria biogenesis and function by modulating the stabilities of nuclear-transcribed mitochondrial mRNAs in response to different carbon sources. Dextrose simulates rapid Puf3p-mediated degradation of its mRNA targets via decay complex recruitment. Ethanol, galactose, or raffinose promotes stabilization of mRNA targets, as Puf3p-mediated decay activity is severely inhibited or abolished. In this work, I have established that carbon source-induced inhibition of Puf3p activity is not due to decreased transcription …

Contribution Of The Mnr2 Protein To Magnesium Homeostasis In Saccharomyces Cerevisiae, Nilambari Prafulla Pisat

Dissertations

Magnesium is an essential metal nutrient with diverse roles in biology. To maintain the optimal function of key biological processes, intracellular Mg2+ concentration is tightly regulated. Despite the importance of this process however, relatively little is known about mechanisms of Mg2+ homeostasis in eukaryotic cells. An understanding of homeostasis starts with defining the function of key transport proteins that allow the passage of Mg2+ ions across the membranes. Yeast geneticists have identified four proteins from Bakers' yeast (Saccharomyces cerevisiae) involved in regulating the accumulation of Mg2+ within the cell (Alr1 and Alr2) and within the mitochondrial compartment (Mrs2 and Lpe10). …

Consequences Of Stochastic Mrna Synthesis In A Gene Regulatory Pathway, Khyati Shah

Dissertations

Gene expression is a stochastic process, with elements of randomness present in both transcription and translation. This stochasticity results in cell-to-cell variation in the amounts of gene products, mRNAs and proteins, and is observed in organisms ranging from bacteria and yeast to higher eukaryotes. Randomness in the activation and inactivation of a gene is the preliminary cause of this variation. At the level of proteins, these variations are buffered compared to levels of mRNA, due to the longer lifespan of proteins. Nevertheless, there is substantial variation observed at the level of proteins, resulting in phenotypic diversity among genetically identical cells. …