Computational Biology Commons^™

Quantifying Genetic Diversity In Nematode Feeding Rate, Jacob King

Honors Theses

Understanding how populations persist under changing environmental conditions is a central question in ecology and evolutionary biology. Variation in traits related to resource acquisition may play a key role in determining population survival when resources are limited or fluctuate over time. In this study, I investigated how variation in feeding-related traits influences population persistence using a combination of computational modeling and laboratory experiments. I developed a stochastic, individual-based consumer–resource model to simulate population dynamics across varying levels of trait variance and resource regimes. Across 60,000 simulated populations, increased trait variation consistently reduced extinction risk and extended persistence time, although the …

Sex In Plants: Birth, Death, And Trying To Survive In Changing Climates, Elena M. Meyer

Theses and Dissertations

Plant mating systems are key determinants of fitness. Angiosperms exhibit a wide variety of reproductive strategies, including self-fertilization (or selfing), outcrossing, and mixed mating. It has been estimated that up to 43% of plant species are capable of selfing, and selfing has been hypothesized to provide reproductive assurance where opportunities for mating may be limited, such as in marginal environments. However, questions regarding the overall distribution of selfing rates across angiosperms, the maintenance of mixed mating in the face of inbreeding depression, and the impact of self-fertilization on diversification rates remain incompletely resolved. Here, we explore the dynamics of self-fertilization …

Systematics Of Disk-Winged Bats (Thyroptera), Courtney L. Klumpp

Capstone Showcase

This thesis investigates the evolutionary relationships among disk-winged bats in the genus Thyroptera, a small group of Neotropical bats known for the adhesive suction disks on their wings and feet that allow them to roost inside tightly rolled leaves. The distinctive morphology and behavior of these bats have not been extensively documented, and their phylogenetic relationships remain only partially resolved. The goal of this research is to better understand how these species are related to one another and to determine whether the five recognized species of Thyroptera form a single monophyletic group. To address this question, morphological and genetic …

Dosage Sensitivity And The Evolution Of Dosage Compensation: Tests Of The Insensitive Sex Chromosome Hypothesis In Flour Beetles, Shana Pau

Biology Dissertations

Sex chromosome evolution generates imbalances in gene dosage that can disrupt gene expression and organismal function. These imbalances are often resolved through dosage compensation mechanisms, yet the factors that drive the emergence and diversity of these systems remain poorly understood. This dissertation addresses a central question in evolutionary genomics: what governs the evolution of dosage compensation?

Focusing on dosage sensitivity as a potential driver, I evaluate the Insensitive Sex Chromosome Hypothesis (ISCH), which predicts that chromosome-wide compensation is more likely to evolve in genomic contexts that are not depleted of dosage-sensitive genes. Using flour beetles (Tribolium spp.) as a …

Population Structure Analysis Of Four Basal Higher-Attines Using Bioinformatic Approaches, Gabriel Mcdanield

Biology Theses

Metapopulations within the family Formicidae are unique among other animals due to the large colonies they build, and the mating strategies required to fertilize a specialized reproductive caste that will often produce young for the life of the colony. One group of ants, the fungus-gardeners (tribe Attini). The population structure of North American non-leafcutting, fungus-gardening ants has been understudied, especially in the southwest of the United States. Additionally, not much is known about their dispersal biology, so the dynamics of dispersal of these species and how they affect population structure is likewise not well known. To shed light on the …

Exploring The Role Of Ecological Traits In Shaping Spatial Patterns Of Genetic Diversity, Rilquer Mascarenhas Da Silva

Dissertations, Theses, and Capstone Projects

The field of comparative phylogeography aims at uncovering common underlying causes for shared patterns of diversity and diversification at the population level. However, it is now widely accepted that intraspecific genetic diversity patterns can differ considerably across co-occurring taxa due to ecological processes acting at the population level (and influencing individual movement and abundance). To model the processes underlying lineage diversification and demographic shifts in response to environmental changes, phylogeographers and population geneticists are now faced with the challenge of incorporating measurements of species ecological traits into their molecular studies. This dissertation aimed at investigating how different types of ecological …

Network Analysis Of Antimicrobial Resistance In Staphylococcus Aureus: Characterization Of Hub Genes And Their Functional Implications, Md Imran Hasan, Davida Smyth, Jeong Yang, Ashley Teufel

Masters Theses (Archived)

Antimicrobial resistance is a major cause of morbidity and mortality in patients with S. aureus infections. In this study, we analyzed genes, molecular mechanisms, and pathways driving drug resistance in S. aureus using network analysis. Using whole-genome sequencing (WGS) data and systems biology approaches, we identified 229 AMR-associated genes and constructed a protein-protein interaction network among these genes. Through network topology and functional enrichment analyses, we not only confirmed their association with resistance, but also highlighted the central roles of these genes in resistance pathways, such as efflux, target replacement, and target protection, which are directly linked to multiple drug …

Chromosome Evolution Model Reveals Hidden Variation In Karyotype-Driven Speciation In Ferns, Thomas Buchloh

All Theses

Because karyotype change commonly generates reproductive isolation between diverging species, rapid karyotype evolution, like that seen in plants, may increase the total rate of diversification. However, few studies have investigated this predicted relationship. Tests of this prediction have identified a positive correlation between the rate of karyotype change (specifically whole genome duplications) and diversification, but tests have been restricted to relatively small and young clades. Fortunately, novel macroevolutionary models have recently become available to investigate patterns of karyotype evolution in large phylogenies, providing new opportunity to investigate variation in karyotype driven diversification. Ferns are one of the most karyotype rich …

Hidden Markov Model For Identifying Local Variants In Human Genomes Using Simulated Data, Scott Mccallum

Electronic Theses and Dissertations

Identifying adaptive mutations in genetic data is challenging due to the low frequency of occurrence of such events, and because signatures of selection are intertwined with the footprints of various other evolutionary forces that shape our genomes. Even when a larger region appears to be under selection, genomic sites that are linked to adaptive mutations have similar statistical signals, and thus can obfuscate the identification of the actual adaptive mutation. The new method described here uses a Hidden Markov Model that allows for classification of neutral, linked, and sweep (adaptive mutation) genomic sites. This model is general and can be …

The Influence Of Environmental Change On Genetic Diversity Across Spatial And Taxonomic Scales, Connor M. French

Dissertations, Theses, and Capstone Projects

The spatial distribution of genetic diversity is of interest to biodiversity scientists and conservationists and is a fundamental metric of biodiversity. Genetic diversity patterns across spatial and taxonomic scales contain information about population and assemblage dynamics that can convey their resilience to environmental change. Ectotherms are especially linked to their environments and may be especially sensitive to fluctuations in the environment over time. Herein, I investigate global and regional patterns of genetic diversity in two groups of ectotherms, insects and lizards, to understand the relationship between environmental change and genetic diversity, from populations to assemblages. Overall, my research aims to …

Evolution And Adaptation To Temperature In Thermotogota, Anne Amelia Farrell

Dartmouth College Ph.D Dissertations

Life thrives across incredibly diverse environmental conditions, yet most organisms are restricted to growing within a narrow range around their optimum growth temperature (OGT). The evolutionary events leading to changes in OGT are poorly understood, and it is uncertain if specific genes are required to thrive at a particular temperature. The bacterial phylum Thermotogota is an excellent model for the evolution of OGT. It comprises mesophilic, thermophilic, and hyperthermophilic members that collectively grow between 20°C and 90°C.

In this work, I analyze the history of OGT in the Thermotogota phylum and show how horizontal gene transfer contributes to the evolution …

Omani Camels From A Cultural And Genomics Perspective, Al Muatasim Al Zadjali

Electronic Theses and Dissertations

The Dromedarian camel, Camelus dromedarius, is native to the Arabian Peninsula, including the Sultanate of Oman. These camels are used for food, milk, as well as show and racing competitions. Despite their economic and cultural importance research on camels in Oman is limited. The goal of this study was to examine their genomic variation, relationship with camels in other parts of the Arabian Peninsula, and to determine if selective breeding has led to the establishment of distinct breeds in Oman. Information was compiled from multiple sources to produce a comprehensive review on the breeding, management, economic and cultural use, …

Avian Symbionts Of Sulawesi: Identifying And Correlating Malaria Parasites And The Microbiome In Communities Of Endemic Avian Hosts, Rachael Joakim

Dissertations, Theses, and Capstone Projects

Since the evolution of complex organisms, there have been communities of symbionts inhabiting them. Thanks to the development of parallel sequencing techniques, DNA of entire microbial communities can be sequenced from a single sample. Some microbes can be parasitic in nature, such as Haemosporida, an order of eukaryotes causing malaria. While most symbionts form a more commensal host relationship in wild systems, host-symbiont dynamics can vary in pathogenicity based on biotic and abiotic factors. In vertebrates, microbial communities in the gut play a major role in host function, including immune responses to Haemosporida. Though this relationship is most commonly explored …

Parental Environnement Influences Offspring Gene Expression In The Olympia Oyster, Ostrea Lurida., Mark S. Yeats

LSU Master's Theses

The Olympia Oyster is the only native oyster species on the Pacific coast of North America. Seasonality in water temperatures across this threatened species’ broad and fragmented range has been linked to its development, reproductive timing, reproductive activity, growth, and survival rates. Recent evidence suggests parental environments can have carry-over effects on larval growth and respiration rates in response to temperature. In this study, we utilized transcriptomic methods to identify the underlying mechanisms of this cross-generation plasticity. Sequence libraries of adult ctenidia tissue and pooled larval replicates were extracted and spawned from hatchery raised oysters of the same parentage immediately …

Understanding The Origin Of Parthenogenesis Via Crossing And Crispr Gene Editing In Daphnia Pulex, Thinh Pham

Biology Dissertations - Archive

Daphnia has been used as a key model system for studying ecological changes, evolution, and genomics for the past few decades due to its rapid turnover time in reproduction. The organism possesses two fascinating modes of reproduction: obligate parthenogenesis and cyclical parthenogenesis. This dissertation delves into the intricate reproductive strategies of Daphnia pulex, focusing on hybrid F1s from different reproductive modes. The first aim is to investigate 31 hybrid F1s generated from obligate parthenogenesis (OP) and cyclical parthenogenesis (CP) parental lines. Transcriptomic analysis reveals misexpression patterns and regulatory divergences, highlighting meiosis-related genes like CDC6 as potential parthenogenesis regulators. The …

A Case Of Incipient Budding Speciation In The California Floristic Province, Infraspecific Divergence In Abronia Villosa, Eli J. Allen

Cal Poly Humboldt theses and projects

Physical barriers to gene flow are the traditional evidence for species divergence. Conversely, there has been increasing acknowledgment of speciation in the face of gene flow as an evolutionary process. Budding speciation involves peripheral populations adapting to local ecological conditions, thereby budding off from a widespread progenitor species. Budding speciation is distinguished by ecological divergence and is generally evidenced by asymmetrical range size and nested phylogenetic relationships of sister species. The narrow endemic Abronia villosa var. aurita is adapted to montane sandy washes adjacent to its widespread sister variety, the desert dwelling var. villosa. Here, I tested the hypothesis …

The Evolution Of The Metazoan Circadian Molecular Mechanism And The Conservation Of Canonical Circadian Elements, Olivia Waldridge

Theses and Dissertations--Biology

The temporal organization of biological activities through circadian rhythms is pivotal for the survival of organisms. Significant progress has been made in understanding the molecular foundations of animal circadian clocks through the characterization of key components such as Clock, Bmal1/Cycle(Cyc), Period (Per), Timeless, and Cryptochrome (Cry) in several model organisms. To determine the universality of this conservation, we investigated the sequences of these genes and their paralogs across 46 animal species that encompass multiple phyla in the metazoan kingdom to resolve the relative timing of duplication and loss events that have diversified core clock components in the metazoan kingdom. Using …

Tracing Evolution Of Gene Transfer Agents Using Comparative Genomics, Roman Kogay

Dartmouth College Ph.D Dissertations

The accumulating evidence suggest that viruses and their components can be domesticated by their hosts, equipping them with convenient molecular toolkits for various functions. One of such domesticated system is Gene Transfer Agents (GTAs) that are produced by some bacteria and archaea. GTAs morphologically resemble small phage-like particles and contain random fragments of their host genome. They are produced only by a small fraction of the microbial population and are released through a lysis of the host cell. Bioinformatic analyses suggest that GTAs are especially abundant in the taxonomic class of Alphaproteobacteria, where they are vertically inherited and evolve …

Acetate Metabolism In The Fungal Pathogen Cryptococcus Neoformans, Oly Ahmed

All Dissertations

Cryptococcus neoformans is an environmental basidiomycetous fungus with a worldwide distribution and a wide range of habitats. Inhalation of the desiccated yeasts or spores of C. neoformans often leads to opportunistic pulmonary infections in immunocompromised individuals, and in severe cases causes lethal meningitis following hematogenous dissemination. During infection, depending on the tissue and disease state, the invading fungi experience a range of nutrient microenvironments within the host body. As a result, rapid metabolic adaptations geared towards efficient utilization of carbon sources alternative to glucose become one of the prime determinants of survival and growth for the pathogen. Incidentally, cryptococcal infection …

Genomic Basis Of Antifreeze Trait Divergence In Antarctic And Patagonian Toothfish, Shriram Bhat

2023 Midwest Ecology & Evolution Conference

The Dissostichus genus of notothenioid fish contains two giant, iconic sister species, Dissostichus mawsoni (Antarctic toothfish) and Dissostichus eleginoides (Patagonian toothfish), which inhabit thermally distinct environments. D. mawsoni is protected by antifreeze glycoproteins (AFGPs) from freezing in the cold waters of the Southern Ocean, while D. eleginoides lacks detectable antifreeze activity despite its recent divergence. Interestingly, recent evidence suggests the possibility of a third species in the Dissostichus genus, which is currently believed to be a separate population of D. eleginoides closer to the Southern Ocean whose genome has recently been published. Our study focuses on D. eleginoides specimens from …

Caribbean Reef-Building Coral-Symbiodiniaceae Network: Identifying Symbioses Critical For System Stability In A Changing Climate, Shaman Patel

All HCAS Student Capstones, Theses, and Dissertations

Increasing global ocean temperatures and frequency of marine heatwaves pose dire consequences for coral reefs. High temperatures often lead to disruptions in coral symbiosis resulting in coral bleaching, increasing the mortality of corals. However, corals can potentially avoid bleaching peril by associating with thermally tolerant symbionts. Here we provide a tool for understanding symbiosis network stability of Caribbean reef-building corals. We created a network of Caribbean hermatypic corals and their associated Symbiodiniaceae phylotypes. A bleaching model was applied to this network to test for resilience and robustness (R50) to thermal stress. It was also layered with trait data for coral …

Development Of Graphical Models And Statistical Physics Motivated Approaches To Genomic Investigations, Yashwanth Lagisetty

Dissertations and Theses (Open Access)

Identifying genes involved in disease pathology has been a goal of genomic research since the early days of the field. However, as technology improves and the body of research grows, we are faced with more questions than answers. Among these is the pressing matter of our incomplete understanding of the genetic underpinnings of complex diseases. Many hypotheses offer explanations as to why direct and independent analyses of variants, as done in genome-wide association studies (GWAS), may not fully elucidate disease genetics. These range from pointing out flaws in statistical testing to invoking the complex dynamics of epigenetic processes. In the …

Plastic And Evolved Responses In The Eastern Oyster, Crassostrea Virginica, To Environmental Variation In The Northern Gulf Of Mexico, Kyle Sirovy

LSU Doctoral Dissertations

Climate change and other anthropogenic impacts are causing rapid alterations to many of the world’s most productive coastal ecosystems and there is an urgent need to understand how species will respond to these environmental changes. Organisms may respond through plasticity, evolution, or the evolution of plasticity. In this dissertation, I evaluate the role of plastic and evolved responses in the eastern oyster, Crassostrea virginica, to environmental variation in the northern Gulf of Mexico. I use comparative transcriptomics, physiology, and morphology to examine the relative contribution of plastic and evolved responses for oysters exposed to low salinity and outplant sites …

Characterizing Endogenous Dicer Products To Unravel Novel Rnai Biogenesis Pathways, Jacob Oche Peter

Dissertations

ABSTRACT

RNA interference (RNAi) is a pervasive gene regulatory mechanism in eukaryotes based on the action of multiple classes of small RNA (sRNA). Exploiting RNAi pathways in non-model systems have great potential for creating potent RNAi technologies. Here, we accessed RNAi-mediated control of gene expression in the two-spotted spider mite, Tetranychus urticae (T. urticae) using engineered dsRNA designed to modulate the host RNAi pathway and increase RNAi efficacy. Analysis of Dicer (Dcr) generated fragments revealed how exogenous RNAs access the host RNAi pathway in this animal, opening avenues for designing RNAi technology for their control. Further, some organisms …

Identifying The Human Homologs Of Yeast Rab Proteins Ypt10 & Ypt11 And A Global-Scale Louse Endosymbiont Genome Variation, Nathaniel P. Smith

Theses and Dissertations

Amyotrophic lateral sclerosis (ALS) is a late-onset fatal neurodegenerative disease that causes loss of upper and/or lower motor neurons, and currently has no treatment or cure available. Over 90% of cases occur spontaneously with unknown causes, highlighting the complexity of the disease, and only 10% of cases are linked to heritable genetic mutations. Numerous ALS-linked genes are conserved through evolution, and model organisms may therefore provide opportunities to understand disease pathology at a molecular or cellular level, proving instrumental in identifying therapeutic targets. ALS subtype 8 (ALS8) is caused by an autosomal dominant P56S mutation in the VAPB gene that …

An Integrative Investigation Of The Synechococcus A/B Clade During Adaptive Radiation At The Upper Thermal Limit Of Phototrophy, Christopher L. Pierpont

Graduate Student Theses, Dissertations, & Professional Papers

Thermophilic microorganisms have been scientifically observed since the early nineteenth century and have spurred many questions about the limits of life and the capacity of organisms to survive extreme conditions. Decades of research on thermophile proteins and genomes have yielded several proposed correlates of temperature that may contribute to adaptation of bacteria and archaea to high temperature. However, many of the generalizations reported are drawn from analyses of deeply divergent taxa or from individual case studies in isolation from mesophilic relatives. Members of the Synechococcus A/B (SynAB) group are the only cyanobacteria with members able to grow above 65 °C …

Getting To The Root Cause: The Genetic Underpinnings Of Root System Architecture And Rhizodeposition In Sorghum, Farren Smith

Graduate Theses, Dissertations, and Problem Reports (ETD)

Plants are some of the most diverse organisms on earth, consisting of more than 350,000 different species. To understand the underlying processes that contributed to plant diversification, it is fundamental to identify the genetic and genomic components that facilitated various adaptations over evolutionary history. Most studies to date have focused on the underlying controls of above-ground traits such as grain and vegetation; however, little is known about the “hidden half” of plants. Root systems comprise half of the total plant structure and provide vital functions such as anchorage, resource acquisition, and storage of energy reserves. The execution of these key …

Comparative Genomics Methods And Applications, Emily N. Alden

Biomedical Sciences ETDs

Virtually all fields of biology have benefited from the advancements in comparative genomics technologies, specifically in the study of evolution. In this dissertation I develop and use comparative genomic technologies to investigate the novel SARS-CoV-2 virus, assembly the first genome of the black lace domestic angelfish and identify germline genetic variants associated with altered breast cancer-specific survival. Our genome tiling array for the novel coronavirus presents a rapid and cost-effective method to sequence the entire viral genome and can be used to track the rapid evolution of viral variants in the population. The domestic angelfish is a member of the …

Genomic And Ecological Dimensions Of Malagasy Reptile And Amphibian Biodiversity, Arianna L. Kuhn

Dissertations, Theses, and Capstone Projects

A long history of isolation coupled with complex topographic and ecological landscapes makes Madagascar ideal for exploring the historical factors that have shaped patterns of population diversity and endemism. Many species-level studies have suggested Late Quaternary climate change may have influenced population dynamics in the tropics, but Madagascar’s ecologically unique biomes or individual species properties may have driven idiosyncratic responses to these shifts. Using community-scale population genetic data I implement a hierarchical approximate Bayesian computation (hABC) approach to evaluate the degree of synchronous population expansion during glacial cycles across herpetofaunal assemblages both within and across discrete biomes and taxonomic groups. …

Quantifying Structure And Variation In Complex Phylogenetic Data, Genevieve Geraldine Mount

LSU Doctoral Dissertations

Identifying the source and structure of variation in nature is crucial to understanding fundamental aspects of evolution. Despite a recent plethora of genetic and morphological data, many interesting questions about the relationships between different groups remain unresolved. My dissertation evaluates three approaches for identifying and quantifying the variation within phylogenetic datasets. Characterizing variation within datasets and across analytical methods gives insight into biologically interesting characters, unusual evolutionary processes, and areas for model improvement.

Network-based community detection approaches offer a powerful tool to describe variation in phylogenetic signal across the genome (i.e., gene tree variation). In Chapter 2, I investigate the …