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Articles 1 - 19 of 19
Full-Text Articles in Life Sciences
A Tree Theory Case Study In Steinernema, Camille Eileen Finlinson Porter
A Tree Theory Case Study In Steinernema, Camille Eileen Finlinson Porter
Theses and Dissertations
It is widely assumed that current phylogenetic methods are fairly accurate at recovering the evolutionary relationships among different species, but evaluating the relative success of this enterprise is a difficult task. This study addresses some fundamental questions associated with generating phylogenetic trees. The complete genomes of five species of Steinernema were sequenced and assembled. Genes were predicted in AUGUSTUS and orthologous genes were found from those data using OrthoMCL. I aligned 3890 genes in MAFFT and eliminated poorly aligned positions with GBlocks. I created individual trees for each gene as well as a supermatrix tree in PAUP*, using a closely …
Characterization Of Sterile Tassel Silky Earl: A Homeotic B-Class Gene Involved In Specification Of Floral Organ Identity In Zea Mays, Steven Keith Williams
Characterization Of Sterile Tassel Silky Earl: A Homeotic B-Class Gene Involved In Specification Of Floral Organ Identity In Zea Mays, Steven Keith Williams
Theses and Dissertations
Specification of floral organ identity in angiosperm flowers is accomplished by the coordinated activity of A-, B-, C-, and E-class MADS-box genes. In the eudicots, B-class genes specify petal and stamen identity. This eudicot B-class function depends on the simultaneous expression of genes from two paralogous B-class lineages (the DEFICIENS/APETALA3 lineage and the GLOBOSA/PISTILLATA lineage). Proteins produced by genes from these two lineages interact as obligate heterodimers and together regulate the transcription of various downstream targets. These obligate heterodimers also positively regulate the transcription of the B-class genes themselves, thereby mediating a unique B-class autoregulatory feedback loop. There is compelling …
Freshwater Phytoplankton Populations Detected Using High Pressure Liquid Chromatography (Hplc) Of Taxon-Specific Pigments, Lauren Jeanne Simmons
Freshwater Phytoplankton Populations Detected Using High Pressure Liquid Chromatography (Hplc) Of Taxon-Specific Pigments, Lauren Jeanne Simmons
Theses and Dissertations
Phytoplankton are key primary producers in aquatic ecosystems, and the principle food source for primary consumers. Individual phytoplankton species respond to different physical, chemical and biological parameters, so monitoring taxonomic composition of the phytoplankton community is a means to monitor changes in environmental conditions. Phytoplankton community changes have frequently been monitored by estimating biomass (using chlorophyll a, measured fluorometrically), and taxonomic data obtained from cell counts. While such methods are useful, they are time-consuming. I hypothesized that high pressure liquid chromatography (HPLC) methods, which have been frequently used in marine systems, would allow separation and identification of key pigments. …
Characterization Of Microsatellite Loci And Pilot Population Genetic Analysis In Hickory Shad, Alosa Mediocris, Fnu Vishakha
Characterization Of Microsatellite Loci And Pilot Population Genetic Analysis In Hickory Shad, Alosa Mediocris, Fnu Vishakha
Theses and Dissertations
The hickory shad (Alosa mediocris) is a relatively understudied species of the anadromous fish sub-family Alosinae. This study, the first population genetic analysis of this species, employed 12 neutral microsatellite loci to estimate genetic diversity and population structure in tributaries of lower Chesapeake Bay, Virginia including James River and its tributaries (Appomattox and Chickahominy Rivers), Rappahannock River, and Pamunkey River. Genetic variation was extremely low. Estimates of observed heterozygosity were lower than expected heterozygosity. Significant population structure was detected among the six samples (FST = 0.093, p = 0.01). Effective population sizes were low (Ne ranged from 2 to 134). …
Ocean Acidification: Understanding The Coastal Carbon Pump In A High Co2 World, Rachel Cooper
Ocean Acidification: Understanding The Coastal Carbon Pump In A High Co2 World, Rachel Cooper
Theses and Dissertations
Since the 1800s, carbon dioxide emissions due to human activities have contributed significantly to the amount of carbon in the atmosphere. Approximately a third of this carbon is absorbed by the ocean, through air-sea fluxes at the ocean surface (Sabine, 2004). Increased CO2 has changed the carbon chemistry of the ocean and hence the pH. pH is expected to drop by 0.4 by the year 2100. It is unclear how this lower pH will affect carbon cycling and sequestration with respect to the biological carbon pump. Most studies have focused on open ocean phytoplankton or bacterial communities in large, stationary …
Effects Of Leaf Litter Diversity On Nutrients And Mosquito Communities In Neotropical Artificial Tree Holes, Rachel Komosinski
Effects Of Leaf Litter Diversity On Nutrients And Mosquito Communities In Neotropical Artificial Tree Holes, Rachel Komosinski
Theses and Dissertations
Inputs from terrestrial habitats to aquatic habitats are important for structuring aquatic communities. Terrestrial producer diversity in the tropics may decline due to anthropogenic causes. I investigated how tree diversity affects aquatic communities. We used leaves from three timber-producing species (Dalbergia retusa, Pachira quinata, and Tectona grandis) to test the effects of leaf litter species composition and richness on invertebrate aquatic communities in Gamboa, Panama. We quantified macroinvertbrate species richness and abundances, leaf litter mass loss, and dissolved carbon to nitrogen ratios (C:N) after 4 weeks. We found that litter types differed in breakdown and C:N. Tectona grandis had lower …
Sex-Specific Habitat Use And Responses To Fragmentation In An Endemic Chameleon Fauna, Philip Shirk
Sex-Specific Habitat Use And Responses To Fragmentation In An Endemic Chameleon Fauna, Philip Shirk
Theses and Dissertations
Chameleons are an understudied taxon facing many threats, including collection for the international pet trade and habitat loss and fragmentation. A recent field study reports a highly female-biased sex ratio in the Eastern Arc Endemic Usambara three horned chameleon, Trioceros deremensis, a large, sexually dimorphic species. This species is collected for the pet trade, and local collectors report males bring a higher price because only this sex has horns. Thus, sex ratios may vary due to differential rates of survival or harvesting. Alternatively, they may simply appear to be skewed if differences in habitat use biases detection of the sexes. …
Evaluating The Performance Of Computational Approaches For Identifying Critical Sites In Protein-Coding Dna Sequences, Matthew Lewis Bendall
Evaluating The Performance Of Computational Approaches For Identifying Critical Sites In Protein-Coding Dna Sequences, Matthew Lewis Bendall
Theses and Dissertations
The ability to link a particular phenotype to its causative genotype is one of the most challenging objectives for biological research. Although the genetic code provides an explicit formula for determining the sequence of amino acid phenotypes produced by a given nucleotide sequence, identifying specific residues that are functionally important remains problematic. Many computational approaches have been developed that use patterns observed in DNA sequences to identify these critical sites. However, very few research studies have used empirical data to test whether these approaches are truly able to identify sites of interest.In most empirical studies, the actual protein function and …
Stoneflies Of Unusual Size: Population Genetics And Systematics Within Pteronarcyidae (Plecoptera), John S. Sproul
Stoneflies Of Unusual Size: Population Genetics And Systematics Within Pteronarcyidae (Plecoptera), John S. Sproul
Theses and Dissertations
Chapter 1. The family Pteronarcyidae (Plecoptera) is a highly studied group of stoneflies and very important to a wide variety of aquatic studies. Several phylogenies have been proposed for this group recent decades, however there is little congruence between the various topologies. The present study revises the phylogeny of the group by combining molecular data from mitochondrial cytochrome oxidase subunit II, ribosomal subunit 12S, ribosomal subunit 16S, and nuclear loci ribosomal subinit 18S and Histone H3, with published morphological data in a parsimony-based total evidence analysis. The analysis produced a well-supported phylogeny with novel relationships within the genus Pteronarcys. …
Diversification And Conservation In The South American Dry Biomes: Distribution Modeling And Multilocus Lizard Phylogeography, Fernanda Werneck
Diversification And Conservation In The South American Dry Biomes: Distribution Modeling And Multilocus Lizard Phylogeography, Fernanda Werneck
Theses and Dissertations
The understanding of diversification of intraspecific lineages can shed light on speciation processes and ultimately biogeographic patterns across multiple spatial and temporal scales. In this dissertation I investigated the geographical and ecological factors promoting diversification across the South American dry diagonal biomes (i.e. Cerrado, Chaco, and Seasonally Dry Tropical Forests - SDTFs), through a coupled approach between multilocus phylogeographic and geospatial methods, in the larger context of interpreting the consequences of the resulting patterns for the conservation of biodiversity and evolutionary processes. In Chapter 1 I evaluate biogeographic hypotheses previously proposed and emphasize that the dry diagonal biomes are particularly …
The Role Of A And B Vitamins During Orofacial Development Of Xenopus Laevis, Allyson Kennedy
The Role Of A And B Vitamins During Orofacial Development Of Xenopus Laevis, Allyson Kennedy
Theses and Dissertations
Orofacial anomalies make up about a third of the 120,000 birth defects each year in the United States. Children born with these abnormalities must undergo immense physical and emotional strain in order to correct the defects. In fact, about $697 million is spent every year surgically treating children with cleft lip and/or cleft palate (2011). In countries where surgery is not an option, this abnormality causes immense difficulties in eating, hearing, speech, and psychosocial development. The causes of cleft lip/palate are extremely complex. Genetics play a role in the anomaly; however, 95% of cleft palate cases are non-syndromic and likely …
Testing Crayfish Evolutionary Hypotheses With Phylogenetic Methods, Jesse W. Breinholt
Testing Crayfish Evolutionary Hypotheses With Phylogenetic Methods, Jesse W. Breinholt
Theses and Dissertations
This dissertation focuses on increasing the understanding of the evolution processes that have contributed to the diversification of freshwater crayfish. Chapter one estimates the divergence time of the three crayfish families and tests the hypothesis that diversification is tied to the break-up of Pangaea, Gondwanna, and Laurasia. I find that the families of crayfish diverged prior to or in association with the break-up of the three super continents. Chapter two addresses the evolutionary history of the genus Cambarus, using molecular data to test hypotheses of relationships based on chela and carapace morphology. The results provide evidence that the morphology used …
Impacts Of Rdx Soil Contamination Across An Age Gradient For The Native Shrub Morella Cerifera., Stephen Via
Impacts Of Rdx Soil Contamination Across An Age Gradient For The Native Shrub Morella Cerifera., Stephen Via
Theses and Dissertations
Understanding the impacts of explosive contamination on vegetation is key to understanding explosives behavior in the environment. I quantified shrub growth responses to 1,3,5-trinitroperhydro-1,35-triazine (RDX) soil contamination across three life stages and I hypothesized that RDX would have the greatest impact on seed germination. Morella cerifera seeds were germinated on soils amended with RDX up to 1500 mg RDX kg-1 dry soil. Juvenile and adult individuals were exposed for 6 weeks to soil amended with RDX up to 750 and 1500 mg RDX kg-1 dry soil, respectively. Morphological responses were quantified for juveniles while physiological measurements were quantified for adults. …
Functional And Biochemical Consequences Of Single Nucleotide Polymorphisms In The Human Vesicular Monoamine Transporter 1 Gene (Slc18a1) By Sally Gamal Shukry, B.S., Sally Gamal Shukry
Functional And Biochemical Consequences Of Single Nucleotide Polymorphisms In The Human Vesicular Monoamine Transporter 1 Gene (Slc18a1) By Sally Gamal Shukry, B.S., Sally Gamal Shukry
Theses and Dissertations
Abstract FUNCTIONAL AND BIOCHEMICAL CONSEQUENCES OF SINGLE NUCLEOTIDE POLYMORPHISMS IN THE HUMAN VESICULAR MONOAMINE TRANSPORTER 1 GENE (SLC18A1) By Sally Gamal Shukry, B.S. A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Biology at Virginia Commonwealth University. Virginia Commonwealth University, 2012 Major Advisor: Jennifer K. Stewart Associate Professor and Graduate Director, Department of Biology Single nucleotide polymorphisms (SNP) in the human VMAT1 gene (SLC18A1) have been associated with schizophrenia in three different populations: Han Chinese, Western European and Japanese. Effects of these mutations on transport function of the hVMAT1 protein have not …
Assessing The Genotoxicity Of Triclosan In Tadpoles Of The American Bullfrog, Lithobates Catesbeianus., David Emery
Assessing The Genotoxicity Of Triclosan In Tadpoles Of The American Bullfrog, Lithobates Catesbeianus., David Emery
Theses and Dissertations
Amphibians are particularly sensitive to environmental degradation and, therefore, serve as effective environmental quality indicators. Research has suggested that amphibian declines are exacerbated by manmade environmental toxicants, especially those found in high concentrations in urban areas. The NIH has pinpointed genotoxicity as a major route of cancer causation, and has since developed stringent testing procedures for potentially hazardous chemicals. One such method, recognized for its simplicity and economy, is the micronucleus assay. A study was conducted assessing the genotoxicity of the widely used antimicrobial agent Triclosan to American Bullfrog tadpoles. Lithobates catesbeianus tadpoles were reared in glass aquaria containing ultra-high …
The Phylogeography Of The Mountain Sucker [Catostomus (Pantosteus) Platyrhynchus], Nina Johanna Laitnen
The Phylogeography Of The Mountain Sucker [Catostomus (Pantosteus) Platyrhynchus], Nina Johanna Laitnen
Theses and Dissertations
Pantosteus, a subgenus of Catostomus, includes the mountain sucker (Catostomus playthyrnchus), whose speculated older origins in the Miocene/Pliocene can provide insight into the ancient geographical events of western North America. We believe that major geologic events influencing the diversification of mountain suckers include the rise of the Colorado Plateau, the connections between the ancient Snake River system and the Lahontan system and subsequently the connection of the Snake River system to the Columbia Basin, dispersal of mountain suckers across the continental divide, as well as the Pleistocene Bonneville flood. If this is true, we should see …
Effects Of Predation Environment And Food Availability On Somatic Growth In The Livebearing Fish Brachyrhaphis Rhabdophora (Pisces: Poeciliidae), Brittany Herrod Gale
Effects Of Predation Environment And Food Availability On Somatic Growth In The Livebearing Fish Brachyrhaphis Rhabdophora (Pisces: Poeciliidae), Brittany Herrod Gale
Theses and Dissertations
Variation in somatic growth rates has interested biologists for decades because of the relationship between growth and other fitness-determining traits (i.e. fecundity, survival, and body size), and the corresponding effect of somatic growth on production of organisms humans use for food. The interaction between genetic variation in growth rates and environmentally induced variation in growth rates shows the pattern of growth across multiple environments (i.e. the reaction norm) that clarifies the history and potential future of evolutionary change in growth rates among populations. Theoretical predictions suggest variation in predator-induced mortality rates can influence mean growth rates and the shape of …
Phylogenetics Of Thysanoptera (Insecta: Paraneoptera), Rebecca S. Buckman
Phylogenetics Of Thysanoptera (Insecta: Paraneoptera), Rebecca S. Buckman
Theses and Dissertations
The order Thysanoptera (Insecta: Paraneoptera), commonly known as thrips, includes organisms that exhibit a wide range of social and feeding behaviors that are of particular interest in evolutionary studies. These studies within thrips have been inhibited by the lack of knowledge of thrips relationships. The recognized classification scheme strives to reflect evolutionary relationships and is based upon morphology. Molecular data is next as morphology alone is not enough to resolve relationships. Few molecular studies have been conducted and all were limited in their taxon sampling and genetic sampling. To provide a foundation of future evolutionary studies, the objectives of this …
Adam10: A Novel Regulator Of Mast Cell Function And Activation, Travis Faber
Adam10: A Novel Regulator Of Mast Cell Function And Activation, Travis Faber
Theses and Dissertations
In this study we show, to our knowledge, the first description of the role ADAM10 plays on mast cells. ADAM10 is abundantly expressed on mast cells both in vitro and in vivo. Its expression is inhibited by IL-10, a suppressive cytokine. siRNA depletion of ADAM10 on bone marrow-derived mast cells (BMMC) caused decreased IL-6 production following IgE cross-linking and also impaired BMMC stem cell factor (SCF)-induced migration through collagen IV. Mast cells and T helper cells (Th cells) in the peritoneum were reduced in ADAM10 KO mice. In addition, ADAM10 KO BMMC produced significantly less of all cytokines measured following …