Thesis (Ph.D.) -- University of Texas at Arlington, 2008.

The biological world is complex. Communities contain a multitude of interacting species, while populations contain extensive genetic variation. How much complexity must one consider to understand patterns and processes of interest? When are species interactions and community properties shaped by evolution? Conversely, when is evolution altered by community context? I test these questions in a series of experiments with simple microbial communities. The first data chapter investigates the impact of competition on the evolution of phage resistance in bacteria. This work demonstrates that community context can dramatically alter the evolution of resistance to phage. Next I tested the impact of evolution on assembly of a three species community. I demonstrate that evolution can influence the content of a microbial community by altering the process of assembly. Finally, I investigated the evolutionary origin and maintenance of cross-feeding mutualisms. This work suggests that species interactions can enable novel evolutionary pathways, and that evolution can significantly increase the productivity of cross-feeding communities. Jointly these experiments suggest that consideration of the interplay between ecological and evolutionary forces can provide insight into the complexity of the natural world. / text

My study investigates Edith Wharton's engagement with Darwin's evolutionary theory in "The House of Mirth" (1905), "The Custom of the Country" (1913), and "The Age of Innocence" (1920). The value of juxtaposing Wharton's narratives with her scientific knowledge has been recognized by critics since the 1950's. Yet, the few existing discussions of Darwinian allegory that examine these novels do not adequately describe the political dimension of Wharton's fictional sociobiology. My investigation addresses this insufficiency in the criticism. Examining Wharton's fiction in relation to her autobiographical writings, letters, and literary criticism, I demonstrate that her major novels link those laws governing gradual change in the natural world—described by Darwin, and theorists such as Herbert Spencer—with the ideological shifts affecting privileged social groupings. The introductory chapter outlines the critical response to Wharton's sociobiology, and examines specific scientific texts that the author refers to in her extra-literary writing. In chapter two I examine "The House of Mirth's" portrayal of cultural practices that lead to the elimination of unfit individuals such as Lily Bart, and show how Wharton critiques the position that natural selection and other laws theorized in The Origin of Species should apply within human society. The following chapter, on "The Custom of the Country", demonstrates Wharton's interest in representing the effects on existing leisure-class cultural practices of the newly-moneyed socioeconomic elite, whose rise Wharton attributes to social evolution. The novel also describes, I show, an inadequate leisure-class ethics that fails to confront the new elite's biological justification for expansion and dominance. Chapter four investigates "The Age of Innocence", in which Wharton takes aim at leisure-class morality by depicting it as a "negation" ( AI 212) of culturally obscured biological instinct, and by representing the sacrifice of individuals to a "collective interest" ( AI 111) that is portrayed as frivolous. In the concluding chapter, I summarize the ways I have extended existing Wharton scholarship, and describe potential pathways for future research. One key conclusion of my dissertation is that Wharton associates ideological change with natural selection, and sexual selection, in order to articulate the challenges to achieving social equality posed by "primitive" (CC 470) and "instinctive" (CC 355) energies.

This thesis examines the development of modern statistical theory and its emergence as a highly specialised mathematical discipline at the end of the nineteenth century. The statistical work of the mathematician and statistician Karl Pearson (1857-1936), who almost singularly created the modern theory of statistics, is the focus of the thesis. The impact of the statistical and experimental work of the Darwinian zoologist W.F.R. Weldon (1860-1906), on the emergence and construction of Pearsonian statistical innovation, is central to the arguments developed in this thesis. Contributions to the Pearsonian corpus from such statisticians as Francis Ysidro Edgeworth (1845-1926), Francis Galton (1822-1911), and George Udny Yule (1871- 1951) are also addressed. The scope of the thesis does not involve a detailed account of every technical contribution that Pearson made to statistics. Instead, it provides a unifying assessment of Pearson's most seminal and innovative contributions to modern statistical theory devised in the Biometric School, at University College London, from 1892 to 1903. An assessment of Pearson's statistical contributions also entails a comprehensive examination of the two separate methodologies he developed in the Drapers' Biometric Laboratory (from 1903 to 1933) and in the Galton Eugenics Laboratory (from 1907 to 1933). This thesis arises, in part, from a desire to reassess the state of the historiography of Pearsonian statistics over the course of the last half century. Some of the earliest work on Pearson came from his former students who emphasised his achievements as a statistician usually from the perspective of the state of the discipline in their tune. The conventional view has presumed that Pearson's relationship with Galton and thus to Gallon's work on simple correlation, simple regression, inheritance and eugenics provided the impetus to Pearson's own statistical work. This approach, which focuses on a part of Pearson's statistical work, has provided minimal insight into the complexity of the totality of Pearsonian statistics. Another approach, derived from the sociology of knowledge in the 1970s, espoused this conventional view and linked Pearson's statistical work to eugenics by placing his work in a wider context of social and political ideologies. This has usually entailed frequent recourse to Pearson's social and political views vis-a-vis his popular writings on eugenics. This approach, whilst indicating the political and social dimensions of science, has produced a rather mono-causal or uni-dimensional view of history. The crucial question of the relation between his technical contributions and his ideology in the construction of his statistical methods has not yet been adequately considered. This thesis argues that the impetus to Pearson's earliest statistical work was given by his efforts to tackle the problems of asymmetrical biological distributions (arising from Weldon's dimorphic distribution of the female shore crab in the Bay of Naples). Furthermore, it argues that the fundamental developments and construction of Pearsonian statistics arose from the Darwinian biological concepts at the centre of Weldon's statistical and experimental work on marine organisms in Naples and in Plymouth. Charles Darwin's recognition that species comprised different sets of 'statistical' populations (rather than consisting of 'types' or 'essences') led to a reconceptualisation of statistical populations by Pearson and Weldon which, in turn, led to their attempts to find a statistical resolution of the pre-Darwinian Aristotelian essentialistic concept of species. Pearson's statistical developments thus involved a greater consideration of speciation and of Darwin's theory of natural selection than hitherto considered. This has, therefore, entailed a reconstruction of the totality of Pearsonian statistics to identify the mathematical and biological developments that underpinned his work and to determine other sources of influence in this development. Pearson's writings are voluminous: as principal author he published more than 540 papers and books of which 361 are statistical. The other publications include 67 literary and historical writings, 49 eugenics publications, 36 pure mathematics and physics papers and 27 reports on university matters. He also published at least 111 letters, notes and book reviews. His collected papers and letters at University College London consist of 235 boxes of family papers, scientific manuscripts and 14,000 letters. One of the most extensive sets of letters in the collection are those of W.F.R. Weldon and his wife, Florence Joy Weldon, which consists of nearly 1,000 pieces of correspondence. No published work on Pearson to date has properly utilised the correspondence between Pearson and the Weldons. Particular emphasis has been given to this collection as these letters indicate (in tandem with Pearson's Gresham lectures and the seminal statistical published papers) that Pearson's earliest statistical work started in 1892 (rather than 1895-1896) and that Weldon's influence and work during these years was decisive in the development and advancement of Pearsonian statistics. The approach adopted in this thesis is essentially that of an intellectual biography which is thematic and is broadly chronological. This approach has been adopted to make greater use of primary sources in an attempt to provide a more historically sensitive interpretation of Pearson's work than has been used previously. It has thus been possible to examine these three (as yet unexamined) key Pearsonian developments: (1) his earliest statistical work (from 1892 to 1895), (2) his joint biometrical projects with Weldon (from 1898-1906) and a shift in the focus of research in the Drapers' Biometric Laboratory following Weldon's death in 1906 and (3) the later work in the twentieth century when he established the two laboratories which were underpinned by two separate methodologies. The arguments, which follow a chronological progression, have been built around Darwin's ideas of biological variation, 'statistical' populations, his theory of natural selection and Galton's law of ancestral inheritance. The first two chapters provide background material to the arguments developed in the thesis. Weldon's use of correlation (for the identification of species) in 1889 is examined in Chaper III. It is argued, that Pearson's analysis of Weldon's dimorphic distribution led to their work on speciation which led on to Pearson's earliest innovative statistical work. Weldon's most productive research with Pearson, discussed in Chapter IV, came to fruition when he showed empirical evidence of natural selection by detecting disturbances (or deviations) in the distribution from normality as a consequence of differential mortality rates. This research enabled Pearson to further develop his theory of frequency distributions. The central part of the thesis broadens out to examine further issues not adequately examined. Galton's statistical approach to heredity is addressed in Chapter V, and it is shown that Galton adumbrated Pearson's work on multiple correlation and multiple regression with his law of ancestral heredity. This work, in conjunction with Weldon's work on natural selection, led to Pearson's introduction of the use of determinantal matrix algebra into statistical theory in 1896: this (much neglected) development was pivotal in the professionalisation of the emerging discipline of mathematical statistics. Pearson's work on goodness of fit testing provided the machinery for reconstructing his most comprehensive statistical work which spanned four decades and encompassed his entire working life as a statistician. Thus, a greater part of Pearsonian statistics has been examined than in previous studies.

Evolutionary processes in any population depend upon patterns of phenotypic variation available to selection and their underlying heritability. In this thesis, I used the filamentous red seaweed Asparagopsis armata, with particular focus on its modularity, to test several key questions underlying its growth-form evolution in heterogeneous environments. I established that experimental manipulations of light quantity and quality mimicking variation in underwater light due to shading or depth induce growthform plasticity in A. armata that may be evolutionarily significant given its variability among clones. Current patterns of plasticity displayed by A. armata appear adaptive, moreover, given that a reciprocal transplant of phenotypes between light environments found densely-branched (phalanx-like) phenotypes to have higher relative growth rates than sparsely-branched (guerrilla-like) phenotypes in well-lit patches, but lower relative growth rates than the latter in shaded patches. Using the capacity for rapid growth as a proxy for fitness, multivariate selection analyses identified environment-dependent patterns of directional selection on single traits coupled with linear and nonlinear selection on multi-trait combinations that shape growth-form variation within patches of differing light intensity, thereby reinforcing plasticity across light environments. Quantitative genetic analyses, however, suggest that the modular iteration of genes in morphogenesis may limit further growth-form evolution in A. armata populations exposed to spatial heterogeneity in light by constraining thallus responses to environment-dependent selection. Last, heritable responses to artificial selection on growth-form variation among clonal cell-lineages revealed the surprising capacity for A.armata to circumvent genetic constraints inherent to its development by adapting to environmental change in the absence of sexually-generated variance among clones.

The release of cells from a biofilm to the surrounding environment is poorly understood and the importance of this stage of biofilm development has only recently been realized. A key part of this process is the generation of phenotypic variants in the biofilm dispersal population. This thesis reports on the characterization of biofilm development of Serratia marcescens MG1, the analysis of the biofilm dispersal population, and the identification of the conditions that trigger phenotypic diversification. Furthermore, it provides an insight into the molecular understanding of how phenotypic variation is being generated, and demonstrates the clinical and environmental implications of phenotypic diversification during bacterial pathogenesis and bacterial persistence. Characterization of the microcolony biofilm development of S. marcescens revealed that the S. marcescens biofilm develops through a process involving microcolony formation, hollowing of mature microcolonies, and a sudden biofilm expansion within a very short period (&lt 24h) resulting in an increase in biofilm biomass with a radiation of biofilm structures at days 3 to 4. The biofilm expansion phase consistently correlated to an increase in the number of dispersal variant morphotypes. Studies of variant induction in planktonic cultures and biofilm flow cells demonstrated that phenotypic diversification in S. marcescens is not only a biofilm-specific phenomenon, but also involves biofilm-specific morphotypes. These morphological variants can only be isolated from the microcolony biofilm morphotype and not from the filamentous biofilms, leading to the hypothesis that there is a strong diversifying selection that is specific to the microcolony biofilms. To further explore how these variants were generated, molecular analyses revealed that exopolysaccharides and lipopolysaccharides are important moieties that are involved in phenotypic variation in S. marcescens biofilms. The etk gene, encoding a tyrosine protein kinase within the exopolysaccharide biosynthesis operon, was found to contain single nucleotide polymorphisms (SNPs) that were present in the 'sticky' variants but not in the 'non-sticky' wild-type or the 'non sticky' small colony variants. Furthermore, infrequent-restriction-site PCR (IRS-PCR), BIOLOG metabolic profiling, and gene sequence analyses, suggest that phenotypic diversification in S. marcescens is likely to involve mutational hotspots in specific genes. The biofilm-derived morphotypic variants differed extensively in cell ultrastructure properties, and exhibited specialized colonization and virulence traits, such as attachment, biofilm formation, swimming and swarming motilities, protease production, and hemolysin production. It was also demonstrated that phenotypic diversification contributed to a varying degree of resistance to protozoan predation, and bacterial pathogenecity in Caenorhabditis elegans, highlighting the complexity of the dispersal populations from S. marcescens biofilms. Furthermore, mixed-culture experiments involving multiple variant isolates (with or without the parental wild-type) showed that the persistence and virulence potential of S. marcescens can be synergistically enhanced in the Acanthamoeba castellanii grazing model and in the C. elegans infection model, respectively. This indicates that the different bacterial morphotypes work in concert to provide S. marcescens with enhanced protection against environmental perturbations and a competitive edge during the infection process. It was proposed that phenotypic diversification is not only an integral part of S. marcescens biofilm life-cycle, but also represents an important strategy for bacteria to greatly enhance its survival and persistence in different environments, ranging from aquatic and soil ecosystems, to those of the infected hosts.

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

Thesis (M.A.)--University of Nevada, Reno, 2007. / "May, 2007." Includes bibliographical references (leaves 53-60). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Nevada, Reno, 2007. / "August 2007." Includes bibliographical references (leaves 80-93). Online version available on the World Wide Web.

Thesis (Ph. D.)--University of Canterbury, 2008. / Typescript (photocopy). Includes bibliographical references (p. 181-193). Also available via the World Wide Web.