Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 134-150).

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 112-124). Also available on the Internet.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Ecology and Evolution." Includes bibliographical references.

Thesis (Ph. D.)--University of Oregon, 2000. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 150-160). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Missouri-Columbia, 2003. / Typescript. Vita. Includes bibliographical references (leaves 112-124). Also available on the Internet.

Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2003. / Vita. Includes bibliographical references (leaves 219-228).

Thesis (Ph. D.)--University of Hong Kong, 1989.

This thesis considers a physical perspective to an insect's maintenance of a clean body surface.  Flying insects are faced with a barrage of particles in their environment, including dust, pollen, pollutants, and parasitic mites, the last of which are responsible for the modern decline of honey bees, of critical importance to agriculture around the world.  In this combined experimental, theoretical, and numerical study, we elucidate the mechanisms by which insects stay clean.  These mechanisms all rely on the insect’s coverage by a dense array of hairs.  We show that these bristles divert incoming flow, reducing deposition of particles, especially onto the eyes.  We replicate this mechanism with microfabricated pillar arrays, demonstrating the feasibility by which they may be incorporated into self-cleaning sensors. During grooming, the bristles on the limbs interact with those on the body and particle removal is achieved through combing and catapulting, driving particles at over 1000 gravities. We show that the three million hairs covering the body of a honey bee are crucial for the efficient removal of accumulated pollen.

Similar forces of selection operating on multiple taxa can cause convergent evolution of quantitative traits. When those same forces of selection occur across an environmental gradient a phenotypic cline may evolve. I have conducted an experiment in central Texas to test whether seed oil melting points and proportions of saturated fatty acids have repeatedly evolved to germinate as predicted by theory. Species with lower seed oil melting points and proportions of saturated fatty acids are expected to germinate at cooler temperatures than ones that germinate at warmer temperatures. Field observations were conducted at two sites for one year to characterize germination temperatures of sixteen species. Gas chromatography was utilized to describe the fatty acid compositions and melting points of those species’ triacylglycerol (oil) stores. The field sites produced conflicting results. At one site, all analyses supported the theory. Whereas evidence from the other site either contradicted expectation or was equivocal. Likewise there was some evidence that plants with annual life histories are under stronger selection to evolve melting points that approximate germination temperature than species with perennial life histories. Finally, evidence was found that a higher level of variation in seed oil melting point and percent of saturated fatty acids is maintained in species that were observed to germinate at low temperatures relative to species observed to germinate at higher temperatures. / text

The tautomerase superfamily (TSF) provides an excellent model system to study enzyme specificity, catalysis, and divergent evolution. trans-3-Cholroacrylic acid dehalogenase (CaaD), cis-3-chloroacrylic acid dehalogenase (cis-CaaD), and malonate semialdehyde decarboxylase (MSAD) are three TSF members that catalyze the final reactions in the degradation of the nematocide, 1,3-dichloropropene. All three enzymes have the TSF characteristic beta-alpha-beta fold and catalytic amino terminal proline (Pro-1). Both CaaD and cis-CaaD dehalogenate their respective isomers of 3-chloroacrylic acid yielding malonate semialdehyde. Subsequently, MSAD decarboxylates malonate semialdhyde resulting in acetaldehyde and CO2. Their catalytic and substrate specificities are exquisite considering they share three key and positionally conserved residues. As part of an effort to understand how such specificity evolved, a pre-steady-state kinetic analysis of CaaD was carried out. Alongside a similar study on cis-CaaD, a fluorescent mutant of CaaD was constructed that had minimal kinetic differences from the wild-type. The mutant was validated as an accurate fluorescent reporter of change in enzyme state that allowed for the reaction to be followed using stopped-flow methods. Stopped-flow fluorescence, rapid chemical quench data and ultraviolet spectroscopy were globally fit by computational simulation. The fit resulted in a kinetic mechanism for CaaD affording detailed information about the reaction, including measuring the rate of product release, the rate of chemistry, a previously unknown partially rate-limiting step associated with a conformational change, and the definition of binding constants for both products (MSA and Br-). In addition to the dehalogenation reaction, the reaction of the fluorescent mutant with a mechanism-based inhibitor, 3-bromopropiolate, was characterized. The values for the apparent rate of inhibition and potency were defined and estimates were determined for the values of the rate of chemistry and the release of bromide. The information gathered during these inhibition experiments was used to further refine the CaaD dehalogenation mechanism eliminating ambiguities present in the initial data set. Finally, the reactions of a cis-CaaD homologue, Cg10062 from Corynebacterium glutamicum were characterized. Cg10062 shares high sequence similarity (53%) and the same six critical active site residues as cis-CaaD, but Cg10062 has poor cis-CaaD activity. Moreover, Cg10062 dehalogenates both 3-chloroacrylic acid isomers. The reactions of Cg10062 with propiolate, 2-butynoate, and 2,3 butadienoate were investigated. Cg10062 functions as a hydratase/decarboxylase using propiolate generating malonate semialdehyde and acetaldehyde. Cg10062 catalyzes a hydration-dependent decarboxylation of propiolate as exogenously added malonate semialdehyde is not decarboxylated. With 2,3 butadienoate and 2-butynoate, Cg10062 functions as a hydratase and yields only acetoacetate. Mutations to the activating residues Glu114 and Tyr103 produced a range of results from a reduction in wild-type activity to a switch of activity. Possible intermediates for the hydration and decarboxylation products can be trapped as covalent adducts to Pro-1 when NaCNBH3 is incubated with certain combinations of substrate and mutant enzymes. Three mechanisms are presented to explain these findings along with the strengths and weaknesses of each mechanism in terms of being able to account for experimental observations. / text