Thesis (Ph. D.)--University of Michigan, 1984. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Morphological variation was examined in 58 species of Canthon and 18 species of other genera of the subtribe Canthonina (Anisocanthon, Canthonella, Cryptocanthon, Deltochilum, Hansreia, Holocanthon, Malagoniella, Melam canthon, Scybalocanthon, and Sylvicanthon). A total of 667 specimens was used for examination of morphological characters. Variation in head structures such as clypeus, eyes, labium, gula, and epipharynx is described. Thoracic structures examined include the pronotum, prosternum, and posterior and medial tibiae. Other structures examined were the elytra, pygidium, and male genitalia, including the sclerites and bushes of the internal sac of the aedeagus. Secondary sexual features (shape of anterior tibial spur and shape of last abdominal segment) were also examined. The characteristics examined include diagnostic characters for the genus Canthon. This analysis revealed that Canthon is a very heterogeneous and artificial group, the limits of which are based on a combination of characters that is not exclusive to genus. Many characters that have been used in the diagnosis of Canthon are general characters that show wide variation within Canthon as well as in other genera of Canthonina. Only a few derived characters were exclusively shared by species of Canthon. However, several genera of Canthonina shared with Canthon some characters, mainly in structures such as the epipharynx and the internal sac of the aedeagus, (epipharynx with two well-defined lateral combs, internal sac with a complete ring-shaped sclerite, reduction in the postero-dorsal aperture of the eye, and reduction in the setae of the anterior margin of the mentum). Due to the fact that the external morphology shows great variation, it is important to consider the study of the other possible sources of characters to resolve the phylogenetic relationships among groups. / Dissertation (MSc (Entomology))--University of Pretoria, 2007. / Zoology and Entomology / unrestricted

Mendelian Randomization (MR) is a powerful tool for accessing causality of exposure on an outcome using genetic variants as the instrumental variables. Much of the recent developments is propelled by the increasing availability of GWAS summary data. However, the accuracy of the MR causal effect estimates could be challenged in case of the MR assumptions are violated. The source of biases could attribute to the weak effects arising because of polygenicity, the presentence of horizontal pleiotropy and other biases, e.g., selection bias. In this thesis, we proposed two works, expecting to deal with these issues.In the first part, we proposed a method named 'Bayesian Weighted Mendelian Randomization (BMWR)' for causal inference using summary statistics from GWAS. In BWMR, we not only take into account the uncertainty of weak effects owning to polygenicity of human genomics but also models the weak horizontal pleiotropic effects. Moreover, BWMR adopts a Bayesian reweighting strategy for detection of large pleiotropic outliers. An efficient algorithm based on variational inference was developed to make BWMR computationally efficient and stable. Considering the underestimated variance provided by variational inference, we further derived a closed form variance estimator inspired by a linear response method. We conducted several simulations to evaluate the performance of BWMR, demonstrating the advantage of BWMR over other methods. Then, we applied BWMR to access causality between 126 metabolites and 90 complex traits, revealing novel causal relationships. In the second part, we further developed BWMR-C: Statistical correction of selection bias for Mendelian Randomization based on a Bayesian weighted method. Based on the framework of BWMR, the probability model in BWMR-C is built conditional on the IV selection criteria. In such way, BWMR-C delicated to reduce the influence of the selection process on the causal effect estimates and also preserve the good properties of BWMR. To make the causal inference computationally stable and efficient, we developed a variational EM algorithm. We conducted several comprehensive simulations to evaluate the performance of BWMR-C for correction of selection bias. Then, we applied BWMR-C on seven body fat distribution related traits and 140 UK Biobank traits. Our results show that BWMR-C achieves satisfactory performance for correcting selection bias. Keywords: Mendelian Randomization, polygenicity, horizontal pleiotropy, selection bias, variation inference.

A primary goal of population genetics is to identify the role of microevolutionary forces in producing observed patterns of molecular and phenotypic variation. I conducted four studies in the northern leopard frog, Rana pipiens, to determine just how mutation, migration, genetic drift, and selection influenced, genetic structure of mitochondrial DNA (mtDNA), nuclear DNA, and a single locus polymorphism that determines dorsal coloration. In the first study, I surveyed the literature concerning color and pattern polymorphisms in anurans. I conclude that anuran polymorphisms remain a rich but largely unexploited system for studying the evolution of phenotypic variation in nature. In the second study, I compared mitochondrial DNA variation from 35 populations distributed across the species' range. A phylogenetic analysis indicated R. pipiens is split into two deeply divergent mtDNA groups, a western group and an eastern group. Phylogeographic and demographic analyses indicated that although restricted gene flow with isolation by distance explained the majority of the processes influencing current genetic structure, population bottlenecks and expansions also played an important role. In the third study, I investigated mtDNA and microsatellite variation in Pacific Northwest populations of R. pipiens, where a recent range contraction had occurred. I found that peripheral populations had reduced levels of genetic variation compared to more interior populations. Moreover, I found that historic samples from peripheral population already had reduced levels of genetic variation. Therefore, low diversity in the remnant populations could not be ascribed to the recent range contraction. In the fourth study, I compared genetic structure from a suite of putatively neutral molecular markers with that derived from the color polymorphism locus. Genetic structure at the color locus, assessed both spatially and temporally, was indistinguishable from structure at neutral loci. This study exemplifies the importance of investigating for evidence of selective maintenance before studies attempt to measure the selective mechanisms maintaining a polymorphism. Overall, my research helps to elucidate how biogeographic and microevolutionary forces influence a wide-spread North American species, R. pipiens. / Graduation date: 2004

Thesis (doctoral)--Universität Bielefeld, 2003. / Includes bibliographical references (p. 147-152).

Thesis (Ph.D.)--Victoria University of Wellington, 2010. / Includes bibliographical references.

Thesis (doctoral)--Rijks-Universiteit te Groningen, 1937. / From: "Genetica", deel 19, alf. 6. Includes bibliographical references (p. 535-536).

Univ., Diss.--Bielefeld, 2003.

Thesis (M.S.)--Rutgers University, 2007. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 38-41).