Ph.D. (Chemistry) / Please refer to full text to view abstract

My thesis focuses on the conservation consequences of the hybridization of Lesser Prairie-Chickens in Kansas. Specifically, examining how past land management practices altering the species ranges impact the distinctiveness of Lesser Prairie-Chickens. Each chapter is an individual publication that addresses if the Greater and Lesser Prairie-Chicken are distinct when applying the morphological and biological species concepts. Chapter 2 compares the evolutionary history and morphological construct of Lesser Prairie-Chickens and other Galliformes using morphometric analysis. Chapter 3 uses low-resolution microsatellite data to reflect recent changes at the population level. This study aims to observe the Greater and Lesser Prairie-Chicken using the morphological and biological species concepts, two of the many species concepts, to determine the distinctiveness and rate of hybridization for these closely related species.

For almost every organism there are large gaps in our knowledge about the processes that leads to speciation. The changes an organism undergoes before divergence has occurred have remained a mystery, as it is difficult to say whether or not a species is going to diverge and when. To investigate this unknown the European whitefish (Coregonus lavaretus) and the northern pike (Esox lucius) were studied, as they produce a repeatable and predictable pattern of speciation in sympatry. To investigate the changes in phenotypes and behaviour in whitefish that precedes divergence, two lake populations were examined, Gräsvattnet and Ringsjön. Gräsvattnet was used as a control, with a population of whitefish but an absence of pike, whereas Ringsjön has a population of whitefish that invaded from Gräsvattnet and a pike population. The presence of pike presumably exerts divergent selection on the whitefish population. Fish and zooplankton were surveyed in both lakes from 1970 to the present day, which allows us to compare how whitefish populations and their resources change in the presence and absence of pike. The results found in Ringsjön show; (1) a change in habitat use, (2) a change in diet from pelagic to benthic, (3) an increase in the relationship between individual body size and diet and (4) a decrease in average size over the course of the study. (1)The presence of pike is believed to have forced the whitefish into the pelagic which could be seen in the result, with an increase in individuals caught in the pelagic. (2) The change in diet is thought to be caused by a resource competition created by individuals being forced to use the pelagic. Although insignificant this led to an overall reduction in zooplankton abundance by almost 40% which could have intensified competition. The resource competition could then have been intensified further by the change in composition of zooplankton relative abundance. (3) The increase in relationship between individual body size and diet is thought to increase due to the resource competition between smaller and larger individuals in the pelagic. Smaller individuals are better competitors than larger individuals for pelagic resource which could have led to the larger individuals switching to a more benthic diet. (4) The decrease in average size is thought to be caused by negative selection for larger individuals. Larger individuals have switched to a more benthic diet, and although the individuals are larger they still face the risk of predation in the littoral zone as they have not outgrown the gape size of the pike. This could have led to the average size reduction that may be the first steps in speciation, and ultimately leading to the divergence of two morphs by sympatric speciation in Ringsjön. In Gräsvattnet over the course of the study there were few and small changes in whitefish size, zooplankton relative abundance in the diet and in the environment. The results in Gräsvattnet could however suggest resource competition for benthic resources. Although resource competition is thought to be an important factor in the speciation of whitefish, without predation pressure no speciation occurs. This result could suggest the importance of predation pressure in the speciation of whitefish.

A general biogeographic theory of insular species diversity, species-energy theory, is produced by replacing area in species-area models with a measure of available energy. Islands with more available energy support larger populations, which have lower extinction rates. Given similar immigration rates, islands with greater available energy are therefore expected to support greater equilibrium numbers of species. Assuming that total population size is proportional to energy supply, and that species-abundance distributions are lognormal and of similar form, the species-energy relationship is approximated by S = kEᶻ. Species-energy theory explains 70-80% of the variation in species number of angiosperms and of birds on such widely varying islands as Greenland and Jamaica. The effects of energy on the structure of a subalpine bee community in Colorado were investigated. As available nector declined, during mornings and over the season, foraging profitability for Bombus appositus (Hymenoptera: Apidae) decreased. This change was manifested by increased foraging trip durations: nector loads did not change. Total colony profits increased as colonies grew over the season, but profit relative to colony size declined, due to reduced profitability of individual foraging trips. These results support the hypothesis of resource limitation in this species. Assemblages of bees foraging on patches of flowers showed effects of energy availability on species composition and dynamics. Bees foraging in enriched patches had lower departure rates than bees in control patches, and, consequently, increased equilibrium numbers of individuals and species present per patch. Both behavioral and mechanical factors influenced departure rates. A species-specific arrival-departure rate model satisfactorily described the foraging assemblages and their response to enrichment. Experiments performed on 2 species of flowers with different corolla tube lengths demonstrated that bee species respond differently to resources of unequal availability, necessitating a species-level approach. Analogies with island systems are discussed. Energy is important to communities in general and bees in particular on a variety of scales. By implication, human resource diversion from natural ecosystems may have profound impacts on global diversity and extinction.

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Thesis advisor: Rudolph Hon / A groundwater plume beneath a capped landfill in north-central Massachusetts contains dissolved arsenic concentrations exceeding 10,000 ppb at several locations. The landfill closed in the early 1990's and contains minimally documented solid waste materials deposited over the course of nearly a century. The source(s), fate, and transport of arsenic in the landfill aquifer have been studied extensively over the past decade; however, the source and pathways of arsenic are not yet fully defined. The primary source of arsenic likely involves a combination of the landfill waste material, the peat, the underlying overburden sequence, and/or bedrock minerals. Arsenic mobilization is most likely assisted by reducing conditions created by the decomposition of organic materials within the landfill and underlying peat present prior to the initiation of waste disposal. Another possibility is an arsenic-bearing groundwater discharging from the underlying bedrock from the oxidation of naturally occurring sulfides. Aqueous arsenic species, including inorganic arsenite [As(III), As(OH)3] and arsenate [As(V), AsO(OH)3], and organic monomethylarsonic acid [MMA(V), CH3AsO(OH)2] and dimethylarsinic acid [DMA(V), (CH3)2AsO(OH)], provide information as to where the arsenic is primarily originating from and how it is transported through the aquifer. Furthermore, the analysis of major ions, metals, and groundwater parameters from different zones of the landfill with varying arsenic concentrations will aid in the delineation of probable arsenic sources, the mobilization processes, and arsenic transport modes within the aquifer. A more complete conceptual site model with respect to arsenic speciation and groundwater chemistry will lead to a better understanding of geochemical processes within and beneath the landfill waste pile and also assist with future remediation of the aquifer. Using arsenic speciation and groundwater chemistry data, it was determined that although all four potential arsenic sources likely contribute to the total arsenic concentrations, the overall contribution from the landfill material, peat layer, and bedrock is minimal relative to the iron-oxyhydroxides coated on the sands particles throughout the aquifer which acts as the primary arsenic source. Oxidation-reduction potential and dissolved oxygen are the controlling factors in relation to mobilization and transport of arsenic species from aquifer features and an understanding of these processes at the local level can be further applied to global-scale arsenic contamination. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Geology and Geophysics.

Speciation is a process by which 1 population splits into 2 distinct populations that in time acquire reproductive isolation (RI). Interestingly, the speed at which RI is attained can be influenced by several factors. My thesis work focuses on how protein-protein interactions affect this process, either by impeding or expediting the acquisition of RI. Here, I present an analysis of cascading positive selection in a group of centromere associated proteins in the Drosophila melanogaster subgroup. Within this group, there are proteins known to interact with rapidly evolving DNA elements located at the centromere, as well as other proteins. While previous work has shown that proteins binding rapidly evolving DNA elements are prone to rapid evolution, I provide evidence that this cascade of positive selection can further extend to other interacting partners. This group of rapidly evolving proteins provides a prime example of protein-protein interactions driving speciation. I also present evidence of protein-protein interactions impeding the process of speciation. Specifically, this work focuses on the sister species D. yakuba and D. santomea. This species pair is of particular interest because previous work has demonstrated that he mitochondrial genome completely introgressed from D. yakuba to D. santomea replacing the native form. By assessing nuclear genes encoding proteins that interact with mitochondrial proteins in the Oxidative Phosphorylation (OXPHOS) pathway, I have identified specific cases of co-introgression in which nuclear encoded mitochondrial partners have introgressed with the mitochondrial genome to allow for the maintenance of physical function, thus maintaining similarities between species, ultimately impeding the process of speciation.

Porphyrins and viologens are often utilized in photocatalyzed electron transfer chemistry. Some of the problems faced by researchers in these applied studies include the lack of information correlating the porphyrin absorbance spectral changes with porphyrin dimerization, complexation, and the effect of noncomplexing cations. In addition, the efficiency of the system is greatly reduced by the formation of porphyrin:viologen association complexes. Knowledge of the values of these constants may allow selection of appropriate porphyrin:viologen concentration ratios which would enable optimization of these systems when used in such applications as artificial photosynthesis. This study reports the effect of selected salts and solvents on the porphyrin spectrum and the spectrum of the H₂TCPP⁴⁻ dimer. Moreover, we define experimental conditions appropriate to the study of porphyrin:viologen association and report association constants calculated at both constant ionic strength and constant buffer concentration. The spectrophotometric titration of tetrakis(pcarboxyphenyl) porphine (H₂TCPP⁴⁻) with either methyl viologen (MV²⁺) or propylviologen sulfonate (PVS⁰) results in the formation of H₂TCPP⁴⁻ :viologen complexes with stoichiometries of both 1:1 and 1:2. In addition, at high viologen concentration, PVS⁰ induces H₂TCPP⁴⁻ dimerization. Association constants for the titration of H₂TCPP⁴⁻ with MV²⁺ were calculated using data obtained at constant ionic strength (I = 0.15, maintained with KH₂P0₄/NaKHP0₄) and at constant buffer concentration ([KH₂P0₄/NaKHP0₄] = 5 mM) using both nonlinear least-squares (NLLS) and principal component analysis (PCA). At constant buffer concentration the association constants calculated via NLLS analysis and PCA were found to be, respectively, 3,170 and 3,350 for the 1:1 complex and 100 and 68 for the 2:1 complex. At constant ionic strength the association constants were calculated by NLLS to be 594 for the 1:1 complex and 38 for the 2:1 complex. PCA was used to confirm our model of the solution equilibrium equations used to calculate the association constants by NLLS analysis. In addition, this method yields the spectral line shape and absorptivity of the spectroscopically unresolved 1:1 H₂TCPP⁴⁻:MV²⁺ complex. From this information it was learned that both the absorptivity and the wavelength dependence of H₂TCPP⁴⁻ and the viologen complexes of H₂TCPP⁴⁻ were a function of the alkali metal cation concentration (higher concentrations of cations result in progressively weakened and blue-shifted spectra). Finally, we will present data which support the conclusion of Firman et al. that the spectrum of the H₂TCPP⁴⁻ dimer is weakened and blueshifted by approximately 10 nm relative to the porphyrin monomer in aqueous solution. We will further show that some organic ions induce H₂TCPP⁴⁻ dimerization and some do not; moreover, we will present experimental evidence demonstrating that the data cannot be explained as a simple effect of the ionic strength.