Thesis (Ph. D.)--University of Wyoming, 2006. / Title from PDF title page (viewed on Dec. 20, 2007). Includes bibliographical references.

The Tamaulipan Biotic Province (TBP) is an ecotonal community that has been characterized in the twentieth century as a mixture of plains, woodland, and desert-adapted mammalian taxa. Some authors have proposed that this heterogeneous mixture of animals is a result of human influence on the environment in the post-European contact period. Others have proposed that the characteristically disharmonious mixture of fauna has been present in south Texas since prehistory. By considering the presence of certain key taxa across the archaeological record of the area this thesis demonstrates that the fauna characteristic of the Tamaulipan Biotic Province can be followed back in time as far as the archaeological record allows. This work also provides complete lists of all vertebrate organisms present in the archaeological record of the area, organized by time period and also by archaeological site and citation.

Seasonal trends in forage production and environmental parameters for five plant community types within a northeastern Oregon riparian zone were described and modeled using correlation and path analysis. Wet meadows produced the greatest amount of herbage biomass, followed by moist bluegrass meadows, gravel bars, forests and dry bluegrass meadows. Trends in soil moisture generally increased and then declined from spring to fall. Depth to the water table declined and then increased. Soil temperatures steadily increased. Variables driving seasonal forage production varied by community type. Soil moisture was most important in dry bluegrass meadows and least important in wet meadows. Depth to the water table was most important in wet meadows and least important in dry bluegrass meadows. The amount of herbage production which had already occurred was also an important variable in describing biomass production. Streamflow levels and the amount of production having occurred were driving variables in the gravel bar communities. Preference for grazing different riparian vegetation community types and forage intake by cattle was monitored over a three-week grazing period occuring at the end of summer. Concurrent to preference and intake, vegetative and nutritional characteristics of the forage available for grazing were monitored and relationships between these variables and both community preference and intake described through correlation and path analyses. Grazing cattle initially favored communities with highly digestibile forage, hence communities dominated by Kentucky bluegrass were most preferred. Late in the grazing period community preference was best associated with community abundance, indicating that cattle were grazing communities in proportion to their abundance in the pasture. Intake levels were greater during the first year of the study than the second (2.15 versus 1.81 percent of body weight). Daily grazing time declined as livestock neared the end of the grazing period. Intake was correlated with in vitro dry matter digestibility and the amount of time spent grazing, but poorly related to the amount of forage available. The indirect effect of the amount of forage available on intake was greater than the direct effect and functioned through increases in grazing time as a result of increased availability of highly digestible forage. / Graduation date: 1992

Plant invasions can ensue when plants are introduced to regions without their specialist enemies (the Enemy Release Hypothesis). This assumes natural enemies limit survival and fecundity in an invader's native range. I tested this assumption for a native invasive species, Common Ragweed (Ambrosia artemisiifolia), by excluding natural enemies from seeds, seedlings and adults. At the adult stage, I added disturbance and conspecific density treatments. Protection from herbivores slightly improved performance at the seedling stage only, while disturbance greatly increased survival and fecundity. Increasing conspecific density reduced performance only in disturbed plots. I also tested herbivore tolerance using simulated damage. Heavy (75%) damage did not reduce fecundity; light damage even increased seed production. These results suggest enemies do not limit Ambrosia in its native range, especially compared to the effects of habitat disturbance. While enemy release may have occurred during Ambrosia’s invasions, it is not likely to be their principal cause.

Plant invasions can ensue when plants are introduced to regions without their specialist enemies (the Enemy Release Hypothesis). This assumes natural enemies limit survival and fecundity in an invader's native range. I tested this assumption for a native invasive species, Common Ragweed (Ambrosia artemisiifolia), by excluding natural enemies from seeds, seedlings and adults. At the adult stage, I added disturbance and conspecific density treatments. Protection from herbivores slightly improved performance at the seedling stage only, while disturbance greatly increased survival and fecundity. Increasing conspecific density reduced performance only in disturbed plots. I also tested herbivore tolerance using simulated damage. Heavy (75%) damage did not reduce fecundity; light damage even increased seed production. These results suggest enemies do not limit Ambrosia in its native range, especially compared to the effects of habitat disturbance. While enemy release may have occurred during Ambrosia’s invasions, it is not likely to be their principal cause.

We previously described BT2, a BTB/POZ domain containing protein, as an activator of telomerase in Arabidopsis thaliana. In the current study, I present evidence of its interesting roles in mediating multiple hormone, stress and metabolic responses in plants. Steady-state expression of BT2 mRNA was regulated diurnally and was under the control of circadian clock, with a maximum expression in the dark. BT2 mRNA was responsive to nutrient status and to multiple biotic and abiotic stress signals. Using bt2 loss-of-function and BT2 over-expressing lines, I show that BT2 suppresses sugar and ABA-mediated responses during germination. BT2 is also essential for transcriptional gene activation mediated by CaMV 35S enhancers in Arabidopsis. Loss of BT2 in several well-characterized 35S enhancer activation-tagged lines such as yucca1d, pap1d, jaw1d etc., resulted in suppression of the activation phenotypes. The suppression of the phenotypes was due to decreased transcription of the activation-tagged genes. I further demonstrate that BT2 genetically interacts with CULLIN3. I propose that BT2 and CULLIN3 are components of a ubiquitin ligase complex. Together with associated proteins BET9 and BET10, the BT2 complex is required for CaMV 35S enhancer-mediated activation of gene expression and may regulate expression of target genes involved in multiple responses to fluctuating biotic and abiotic conditions. I also found that BT2 protein levels are tightly regulated in plants. BT2 protein was primarily localized in the nucleus and was developmentally regulated. BT2 turn-over was regulated in part by the 26S-proteosome, and rare codons present in its open reading frame affected BT2 protein accumulation. In addition to BT2, its orthologs, BT1, BT3, BT4 and BT5, also responded to light, clock and nutrients, with some differences. Moreover, BT1, BT3 and BT4 were also required for 35S enhancer-mediated activation of gene expression. I propose that BT family proteins assemble into multi-protein complexes to mediate multiple responses to changing environmental and nutritional conditions.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on January 19, 2010). Thesis advisor: Dr. Charles F. Rabeni. Includes bibliographical references.

Thesis (M.S.)--California Polytechnic State University, 2010. / Title from PDF title page; viewed on March 18, 2010. Major professor: Royden Nakamura, Ph.D. "Presented to the faculty of California Polytechnic State University, San Luis Obispo." "In partial fulfillment of the requirements for the degree [of] Master of Science in Biological Sciences." "February 2010." Includes bibliographical references (p. 78-90).

Thesis (Ph. D.)--University of California, San Diego, 2000. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Dept. of Ecology and Evolution, August 2003. / Includes bibliographical references. Also available on the Internet.