Biology Commons^™

Ecosystem Impacts Of The Invasive Shrub Lonicera Maackii Are Influenced By Associations With Native Tree Species, Megan Marie Poulette

Theses and Dissertations--Biology

Invasive species are significant drivers of global environmental change, altering the stability and functioning of numerous ecosystems. The exotic shrub Lonicera maackii is an aggressive invader throughout much of the eastern United States. While much is known about its population and community impacts, little is known about effects on ecosystem processes.

This dissertation documents changes in ecosystem processes associated with L. maackii growing beneath three native tree species (Fraxinus quadrangulata, Quercus muehlenbergii, Carya ovata) in a savanna in Kentucky. Like many invasive plants, L. maackii litter decomposed and lost nitrogen (N) rapidly, especially in comparison with …

The Biology And Management Of Brucellosis In Yellowstone Bison, John Joseph Treanor

Theses and Dissertations--Biology

Disease management along the boundaries of wildlife reserves is a growing conservation problem worldwide, as infected wildlife can migrate outside protected areas and pose a threat to livestock and human health. The bison Bison bison population in Yellowstone National Park has long been infected with Brucella abortus, the bacterium causing bovine brucellosis. Concern over migratory bison transmitting B. abortus to cattle herds on lands adjacent to Yellowstone has led to proposals for bison vaccination. Model simulations suggest that vaccination is unlikely to eradicate B. abortus from Yellowstone bison but could be an effective tool for reducing the level of …

Ecology Of Mating Patterns And Sexual Selection In Dickcissels Breeding In Managed Prairie, Bridget Frances Sousa

Theses and Dissertations--Biology

Males of many species have elaborate phenotypes that are absent in females and that are thought to be the result of sexual selection. Sexual selection requires: (i) variance in male mating success, (ii) variation in male phenotype, and (iii) covariation between male mating success and male phenotype. Environmental conditions influence these factors, and management practices that alter environmental conditions have the potential to shape mating patterns and sexual selection. I investigated the hypothesis that the frequency of fire, used to manage tallgrass prairie, affects the mating patterns and process of sexual selection in the organisms breeding in managed prairies.

I …

The Ecological And Evolutionary Effects Of Endocrine Disrupting Compounds On Sexually Selected Traits In Male Guppies, Kausalya Shenoy

Theses and Dissertations--Biology

Male mating signals convey important mate-quality information to females and are regulated by androgens. Endocrine disrupting compounds (EDCs) are chemicals that interfere with proper hormonal functioning in exposed animals, causing altered hormone levels and resulting in changed reproductive characteristics, including mating signals. Altered signals can have ecological implications by influencing population and community dynamics and evolutionary implications via trans-generational reduction in signal reliability leading to reduced preference and eventual loss of the signal trait. I examined the effects of exposure to environmentally relevant concentrations of atrazine, a widely used herbicide and EDC, on mating signals and behaviors in male guppies, …

Central And Peripheral Regulation Of Circadian Gastrointestinal Rhythms, Jaclyn Malloy

Theses and Dissertations--Biology

Circadian clocks are responsible for daily rhythms in gastrointestinal function which are vital for normal digestive rhythms and health. The present study examines the roles of the circadian pacemaker, the suprachiasmatic nuclei (SCN), and the sympathetic nervous system in regulation of circadian gastrointestinal rhythms in Mus musculus. Surgical ablation of the SCN abolishes circadian locomotor, feeding, and stool output rhythms when animals are presented with food ad libitum, while restricted feeding reestablishes these rhythms temporarily. In intact mice, chemical sympathectomy with 6- hydroxydopamine has no effect on feeding and locomotor rhythmicity, but attenuates stool output rhythms. Again, restricted …

Investigating The Ped Protein And Its Effect On Translational Control In Drosophila Melanogaster Spermatogenesis, David C. Keesling

Theses and Dissertations--Biology

Inactive mutants of the ped gene cause two phenotypes in Drosophila melanogaster: male sterility and the early translation of DHODH within spermatogenesis. Investigation of the PED amino acid sequence revealed an OTU domain and an ubiquitin interacting motif, suggesting that it is a member of the otubain sub-family of de-ubiqutinating enzymes. To test this, the putative active cysteine residue was mutated. Results show that this single cysteine residue is required for ped to confer male fertility. Purified wild type PED was also used to carry out in vitro deubiquitinating assays. These assays failed to show any ability for PED …

When Molecules And Morphology Clash: Revisiting Species Tree Reconstruction Of Ambystomatid Salamanders Using Multiple Nuclear Loci, Joshua Steven Williams

Theses and Dissertations--Biology

The analysis of diverse data sets can yield different phylogenetic estimates that challenge systematists to explain the source of discordance. The Ambystomatidae are a classic example of this phylogenetic conflict. Previous attempts to resolve the ambystomatid species tree using allozymic, morphological, and mitochondrial sequence data have yielded different estimates, making it unclear which data source best approximates ambystomatid phylogeny. We present the first multi-locus DNA sequencebased phylogenetic study of the Ambystomatidae. Because independent loci can contain discordant gene tree histories, concatenating unlinked loci into a single data matrix can lead to strongly supported and erroneous results. Therefore, we utilized a …

The Effects Of Spatial Configuration Of Populations On The Maintenance Of The Sexes In A Clonal Organism, Christopher Stieha

Theses and Dissertations--Biology

Despite the two-fold advantage to asexual reproduction and its prevalence in a variety of organisms, sexual reproduction is prevalent across all taxa. The maintenance of two sexes is required to ensure genetic diversity and to prevent “evolutionary dead ends,” especially in clonal organisms. Many mechanisms have been proposed for the maintenance of two sexes, ranging from environmental variation and stochasticity, parasites and predators, and mutation rates. Spatial configuration, the size and location of populations with respect to other populations, can allow two competitors to coexist when one would normally be lost. This is especially important when the two competitors are …

Empirical And Conceptual Approaches To Life-History Trade-Offs: The Size And Number Of Offspring In Broods Of A Parasitoid Wasp, Yoriko Saeki

Theses and Dissertations--Biology

Trade-offs in resource allocation underlie key life history traits of organisms. My dissertation focuses on the size-number trade-off in clonal broods of offspring using the polyembryonic wasp, Copidosoma bakeri parasitizing immature stages of the moth Agrotis ipsilon. I aim to characterize responses of wasp brood size and individual body mass by manipulating the environments in order to understand the allocation pattern in the size number trade-off. In reviewing the functional forms of trade-off relationships in relation to resource constraints, I distinguish among three main trade-off types based on graphical representations of the relationship between the trade-off variables: linear, convex …