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Articles 1 - 21 of 21
Full-Text Articles in Life Sciences
Zooplankton Abundance, Community Composition And Grazing In The James River Estuary (Virginia, Usa), Laura E. Barry
Zooplankton Abundance, Community Composition And Grazing In The James River Estuary (Virginia, Usa), Laura E. Barry
Theses and Dissertations
This study examined the extent to which zooplankton in the James River Estuary (Virginia, USA) exploit the available algal-food resources. Zooplankton abundance, community composition and grazing rates were assessed at three locations which included a site with high algal production (near the VCU Rice Center) and two sites where algal production was lower. Grazing rates were measured by determining the rate of phytoplankton decline (as chlorophyll a) during 48-hour incubation experiments in the presence and absence of zooplankton. Significant differences in zooplankton abundance were observed among the three sites, with the greatest average zooplankton density (434 ± 69 ind/L) occurring …
Examining The Effects Of Penning On Juvenile Eastern Box Turtles (Terrapene Carolina Carolina), Nicolas Frederick
Examining The Effects Of Penning On Juvenile Eastern Box Turtles (Terrapene Carolina Carolina), Nicolas Frederick
Theses and Dissertations
Box turtle (Terrapene carolina) populations have been declining over the last several decades, and one major cause is increasing urbanization. As a result of habitat fragmentation, wildlife managers are frequently turning to new and alternative management strategies. Traditional box turtle management has included relocation, which has been met with limited success. This study aims to combine these strategies with another less-studied one: forcing turtles to overwinter on site by penning them in an outdoor enclosure. Two sets of juvenile box turtles were released at the Virginia Commonwealth University Rice Center: one penned on site in a pen for one year, …
Prothonotary Warbler (Protonotaria Citrea) Plumage As An Indicator For Infection: The Relationship Between Haemosporidia Infection And Breast Feather Reflectance In A Neotropical Migrant Passerine, Robert Fithian
Theses and Dissertations
Yellow avian plumage is a direct result of carotenoid pigments obtained in a bird’s diet and may act as an indicator for individual health, parasite resistance, and status. This study describes breast feather reflectance of adult Prothonotary Warblers (Protonotaria citrea) (n=169), insectivorous Neotropical migrant passerines, throughout the Ultraviolet (UV) and human visible light spectra and examines the relationship between Haemosporidia (pathogen causing Avian Malaria) infection and feather reflectance (n=41). Reflectance was characterized using a Principle Component Analysis evaluating Intensity, Brightness, Hue, UV Intensity, UV Brightness, and UV Chroma. UV and visible light reflectance was higher in birds sampled earlier in …
Systematics And Biogeography Of The Didymopanax Group Of Schefflera (Araliaceae), Pedro Fiaschi
Systematics And Biogeography Of The Didymopanax Group Of Schefflera (Araliaceae), Pedro Fiaschi
Theses and Dissertations
Schefflera is the largest genus in the angiosperm family Araliaceae, with about 900 species, of which c. 300 belong to five subgeneric groups in the Neotropical region. Previous phylogenetic studies of Schefflera have been limited to a small number of species from this region, and very little is know about phylogenetic relationships in the Brazilian-centered Didymopanax group of this genus. Therefore, to gain a better understanding of the diversity and evolution of the Didymopanax group of Schefflera, I investigated the systematics of these plants in the broader context of the entire Neotropical clade. The main goals were (1) to investigate …
Effects Of Biofilm Age And Composition On Oyster Larval Setting, Alaina Hart
Effects Of Biofilm Age And Composition On Oyster Larval Setting, Alaina Hart
Theses and Dissertations
The lack of success in restoring oyster, Crassostrea virginica, populations to Chesapeake Bay and its tributaries has raised many questions about why many restoration efforts have failed. A number of studies have focused on the larval stage of oysters and considered the variables that impact oyster setting behavior in an effort to understand why oyster populations have not recovered. Studies that have examined setting surfaces suggest that biofilms promote oyster larval settlement; however, similar studies with barnacle larvae have found an inhibitory relationship. The present study utilized field-produced biofilms of different ages to determine if natural biofilms inhibit or promote …
Genetic Differentiation Of The Parasitoid, Cotesia Congregata (Say), Based On Host-Plant Complex, Georgia Karns
Genetic Differentiation Of The Parasitoid, Cotesia Congregata (Say), Based On Host-Plant Complex, Georgia Karns
Theses and Dissertations
Endoparasitoids of herbivorous lepidopterans have intimate relationships with their host species as well as the plant on which their host develops. Characteristics of both hosts and plants can affect parasitoid success in tri-trophic systems and thus, drive diversification. Genetic differentiation was estimated for Cotesia congregata (Say) collected from two distinct host-plant complexes, Manduca sexta L. on tobacco (Nicotiana tabacum L.) and Ceratomia catalpae, (Haworth) on catalpa (Catalpa bignonioides Walker), in the mid-Atlantic region of North America using seven microsatellite loci and the mitochondrial COI locus. Microsatellite allele frequencies were differentiated based on host-plant complex, and COI haplotypes from individuals on …
Assessment Of Pre-Pcr Whole Genome Amplification Of Single Pollen Grains Using Flowering Dogwood (Cornus Florida), Candace Dillon
Assessment Of Pre-Pcr Whole Genome Amplification Of Single Pollen Grains Using Flowering Dogwood (Cornus Florida), Candace Dillon
Theses and Dissertations
Studies of gene flow in natural plant populations often focus on either historical or abiotic dispersal methods (e.g. wind, water, gravity), but there is little information available on contemporary, animal-mediated pollen dispersal patterns. Emerging molecular laboratory techniques allow unprecedented insights into spatial patterns of pollen-mediated gene flow. However, to date, technical challenges have limited their widespread application. The genome of a pollen grain can be amplified via whole genome amplification (WGA) prior to traditional amplification via polymerase chain reaction (PCR) to prevent the stochastic effects associated with low copy number amplification. Even still, WGA can suffer from low success rates …
Understanding The Genetic Consequences Of Rapid Range Expansion: A Case Study Using The Invasive Microstegium Vimineum Trin. (Poaceae), Stephen Baker
Understanding The Genetic Consequences Of Rapid Range Expansion: A Case Study Using The Invasive Microstegium Vimineum Trin. (Poaceae), Stephen Baker
Theses and Dissertations
Global temperature changes are predicted to influence the distributions of plants and can have significant consequences for population genetic structure. Both the nature of these consequences and the processes that shape them are of interest for both conservation genetics and the development of realistic management programs. Rapid range expansion occurs on short temporal scales not conducive to conventional phylogeographical analyses. This paper presents the findings from a population genetic study of the invasive grass Microstegium vimineum Trin. A. Camus throughout the James River Basin of Virginia. Genotypic analysis using Amplified Fragment Length Polymorphism (AFLP) molecular markers were used to test …
An Evaluation Of Bacterial And Fungal Contributions To Organic Matter Decomposition Along A Soil Moisture Gradient, Morgan Rawls
An Evaluation Of Bacterial And Fungal Contributions To Organic Matter Decomposition Along A Soil Moisture Gradient, Morgan Rawls
Theses and Dissertations
The decomposition of plant litter is a critical biological function that aids in nutrient cycling and energy transfers within and between ecosystems. The primary decomposers of dead leaf material are bacteria and fungi, though there is no consensus as to which of these groups is dominant, nor is it known how the abundance and composition of these communities changes over time. The objectives of this study were to examine the relative contributions of bacterial and fungal populations to leaf organic matter (OM) decomposition and to consider the effect of moisture availability on the microbial community. The study was conducted across …
Presence Of Haemosporidia And Flaviviruses In Breeding Prothonotary Warblers (Protonotaria Citrea): An Analysis Of Spatial And Temporal Trends In Infection Prevalence And Associations With Reproductive Success, Elena Grillo
Theses and Dissertations
As Neotropical migratory birds, Prothonotary Warblers are exposed to parasites in both tropical and temperate regions and may act as dispersal agents between geographic areas. This study identifies the prevalence of Haemosporidia, West Nile Virus (WNV), and St. Louis Encephalitis virus (SLEV) in this species. A total of 71.6% of captured Prothonotary Warblers were infected with Haemosporidia during the 2008 breeding season, and infection prevalence increased throughout the season. This temporal change in prevalence is likely due to infection relapse and transmission of new infections. No correlations between reproductive effort and infection status were observed, nor were any associations between …
Predator And Abiotic Effects On Hatching Phenotype And Survival Of Arboreal Frog Eggs With Implications For Phytoplankton, Jessica Hite
Predator And Abiotic Effects On Hatching Phenotype And Survival Of Arboreal Frog Eggs With Implications For Phytoplankton, Jessica Hite
Theses and Dissertations
Historically studies have focused on either the terrestrial or aquatic environments independently. However, these systems are inherently linked through numerous pathways including organisms with complex life cycles. Both abiotic factors and predators of these organisms can influence connections by changing the number of prey moving across habitat boundaries and by changing the phenotype of prey. When the focal organisms are primary consumers, these effects may have important implications for ecosystem processes. My study investigated how terrestrial predators and abiotic factors affect the number and phenotype of herbivorous tadpole inputs into a tropical forest pond. I found that predators and abiotic …
Influence Of Salinity Variations On The Desorption And Lability Of Soil Organic Carbon Associated With Tidal Freshwater Marshes, Lindsey Michelle Koren
Influence Of Salinity Variations On The Desorption And Lability Of Soil Organic Carbon Associated With Tidal Freshwater Marshes, Lindsey Michelle Koren
Theses and Dissertations
Tidal freshwater marshes (TFMs) are unique ecosystems that bridge the gap between terrestrial and aquatic ecosystems and are important in the sequestration of soil organic carbon. With the ever changing global climate, TFMs are left vulnerable to downstream effects of rising sea level and salt water intrusion due to increases in flooding by saline waters. These changes often act over large spatial and temporal scales resulting in significant impacts to local and regional environments. This multidisciplinary study assessed the amount and lability of desorbed organic carbon in tidal freshwater marsh soils from the Waccamaw River Marsh, South Carolina and Sweet …
Consequences Of Shrub Encroachment: Linking Changes In Canopy Structure To Shifts In The Resource Environment, Steven Brantley
Consequences Of Shrub Encroachment: Linking Changes In Canopy Structure To Shifts In The Resource Environment, Steven Brantley
Theses and Dissertations
Shrub expansion in herbaceous ecosystems is emerging as an important ecological response to global change, especially in mesic systems where increases in canopy biomass are greatest. Two consequences of woody encroachment are increases in belowground resources, such as carbon and nitrogen, and reductions in above-ground resources such as light, which affect diversity, community trajectory, and ecosystem function. My objective was to determine how expansion of the nitrogen-fixing shrub Morella cerifera affected the resource environment across a chronosequence of shrub expansion on a Virginia barrier island. I quantified changes in carbon (C) and nitrogen (N) cycling, canopy structure and understory light …
The Presence Of Amphibian Ranavirus In Virginia Warm Water Fish Hatchery Ponds, Elizabeth Nelson
The Presence Of Amphibian Ranavirus In Virginia Warm Water Fish Hatchery Ponds, Elizabeth Nelson
Theses and Dissertations
Amphibian declines have been occurring world wide over the past several decades. Infectious disease and environmental changes have been implicated as the causative agents in these declines. Fish stocking from hatcheries provides a unique opportunity for organisms, including infectious diseases, to travel over long distances. Ranavirus was previously found in two ponds at Harrison Lake National Fish Hatchery in Charles City County, Virginia. Therefore, the primary objective of this study was to determine if ranavirus is present in tadpoles from four warm water fish hatcheries in Virginia. A secondary objective of this study was to determine if there are relationships …
Generation Of Macrophage Chemotactic Factors By Spla2, Andria Chambers
Generation Of Macrophage Chemotactic Factors By Spla2, Andria Chambers
Theses and Dissertations
Removal of apoptotic cells by macrophages is required in order to prevent autoimmune responses. Previous studies have reported that group IIA secretory phospholipase A2 (sPLA2) preferentially binds to apoptotic cells and induces a chemotactic factor which promotes the migration of macrophages to apoptotic cells. Based on these observations, we hypothesized that the pool of sPLA2 trapped on apoptotic cells produces chemoattractant lipids that recruit macrophages to phagocytose the apoptotic cells. To test this hypothesis, Jurkat cells were cultured under normal conditions and induced to undergo early apoptosis through treatment with D,L-threo-dihydrosphingosine. Live and early apoptotic cells were incubated with catalytically …
Factors Affecting Dissolved Oxygen Metabolism In Coastal Plain Streams Of Virginia, Julie Frank
Factors Affecting Dissolved Oxygen Metabolism In Coastal Plain Streams Of Virginia, Julie Frank
Theses and Dissertations
I investigated seasonal and inter-site variation in factors influencing diel dissolved oxygen (DO) metabolism at four streams in the Virginia Coastal Plain. Data were collected monthly from January to August 2008 to characterize DO metabolism (diel DO amplitude, production, respiration), incident solar radiation (PAR), dissolved nutrients, fine benthic materials (mass, C:N, Chlα) and hydrology (discharge, water transit time, transient storage). Reach-scale metabolism estimates were determined using the one-station diurnal DO technique and transit time and transient storage were determined by conservative tracer additions. Incident solar radiation was the primary determinant of DO metabolism as streams experiencing higher light levels (Herring …
Coupling Of Autotrophic And Heterotrophic Plankton Food Web Components In The Tidal-Freshwater James River, Usa, Matthew Beckwith
Coupling Of Autotrophic And Heterotrophic Plankton Food Web Components In The Tidal-Freshwater James River, Usa, Matthew Beckwith
Theses and Dissertations
Empirical studies have shown that algal- and detrital-based food web components are coupled in many pelagic systems as algal carbon enhances bacterioplankton production and growth efficiencies. Such phyto-bacterioplankton coupling impacts carbon flow through plankton food webs, yet the extent of coupling is poorly understood in systems receiving large amounts of allochthonous carbon. To investigate this issue, bacterioplankton abundance (BA) and community composition were compared to chlorophyll a concentrations and phytoplankton production in the tidal-freshwater James River (VA). BA averaged 107 cells mL-1 and was significantly related to chlorophyll a, phytoplankton production, and DOC concentrations. Analysis of DOC quality using fluorescence …
Identification Of Binding Partners Of A Novel P. Falciparum Exported Protein, Monica Zapata
Identification Of Binding Partners Of A Novel P. Falciparum Exported Protein, Monica Zapata
Theses and Dissertations
Plasmodium falciparum is the causative agent of the most severe form of malaria. This parasite drastically modifies its host cell, the erythrocyte, to create a hospitable environment for its growth and reproduction. In order for these modifications to occur, the parasite secretes proteins into the erythrocyte. While the secretion machinery is still unknown, many secreted proteins have been found to have a hydrophobic signal sequence and a novel host-targeting signal downstream of the hydrophobic sequence. A novel P. falciparum protein has been shown to be secreted from the parasitophorous vacuole, yet it lacks both a hydrophobic signal sequence and a …
The Role Of Mitogen-Activated Protein Kinases In The Regulation Of Plant Development, Erica Satterfield
The Role Of Mitogen-Activated Protein Kinases In The Regulation Of Plant Development, Erica Satterfield
Theses and Dissertations
Mitogen-activated protein kinases are part of an evolutionarily conserved protein phosphorylation cascade which serves essential regulatory functions in eukaryotic organisms. Although the role of MAPKs in the regulation of a plant’s response to environmental stress and plant defense has been well established, very little is known about their role in the regulation of plant developmental processes. In order to examine the role of MAPKs in plant growth and development, a strong mammalian MAPK phosphatase (MKP-1), which is known to inactivate MAPKs in plants, was introduced into tobacco plants. In tobacco plants, MKP-1 overexpression altered plant responses to the phytohormones, ethylene …
Identification Of Camk-Ii Protein Targets In Tissue Culture And Zebrafish Embryos Using Tandem Mass Spectrometry, Alexandra Myers
Identification Of Camk-Ii Protein Targets In Tissue Culture And Zebrafish Embryos Using Tandem Mass Spectrometry, Alexandra Myers
Theses and Dissertations
Calcium (Ca2+)/calmodulin-dependent kinase 2 (CaMK-II) is one member of a family of Ca2+/calmodulin-dependent protein kinases that responds to intracellular Ca2+ signals (Hudmon, A. and H. Schulman (2002)). CaMK-II is a multifunctional regulator of transcription, cell cycle progression, cell motility and neuronal development. (Wang, C., et al. (2008), Easley, C. A. IV, et al. (2008), Osterhoff, M., et al. (2003), Faison, M. O., et al. (2002)). Recently, CaMK-II has been shown to be important in the early development of vertebrates. In developing zebrafish, disruption of CaMK-II expression has been shown to induce phenotypes similar to those documented in several human diseases. …
Spatial And Temporal Variability Of Macroinvertyebrate Communities In Vernal Pools On The Coastal Plain Of Virginia, Shrijeeta Ganguly
Spatial And Temporal Variability Of Macroinvertyebrate Communities In Vernal Pools On The Coastal Plain Of Virginia, Shrijeeta Ganguly
Theses and Dissertations
Vernal pools are often defined as seasonal pools that typically are inundated beginning in the winter and then drying out completely in summer. Though evidence of spatial and temporal variability in the macroinvertebrate communities of vernal pools has been found in previous studies, it has not been studied extensively. The primary objective of this study was to determine the extent of variability in the macroinvertebrate communities within vernal pools closely situated in a forested landscape. An effort was made to explain this variability with respect to certain physiochemical environmental variables of the pools. Significant variability was observed in the macroinvertebrate …