Life Sciences Commons^™

The Evolution Of Kin Recognition, Timothy Ja Hain

Electronic Thesis and Dissertation Repository

The discovery that many animals are promiscuous has challenged the importance of Hamilton’s Rule because it reduces the net benefits of helping nestmates. To resolve this challenge, biologists have investigated animals’ abilities to determine degrees of relatedness among individuals using kin recognition mechanisms. I conducted a literature review and found that most animals use one of two mechanisms: “familiarity” whereby kin are remembered from interactions early in life, such as in a nest, or “phenotype matching” whereby putative kin are compared to a template of what kin should look, smell, or sound like based on relatives encountered during early life …

A New Adaptive Landscape: Urbanization As A Strong Evolutionary Force, Lauren Christie Breza

Masters Theses

Urbanization is rapidly increasing as human population growth steadily grows, but there is little consensus of the ecological consequence of this population shift and almost no information of the evolutionary consequences for local biodiversity. Nearly two-thirds of the world’s population will live in city centers by 2050 with profound impacts on landscapes that can act as important agents of selection. This study aims to identify 1) the net effect of urbanization on species richness, 2) how phylogenetic diversity varies between urban and rural sites, and 3) the strength of urbanization as a selection pressure. First, a meta-analysis was conducted in …

Virulence Of Photorhabdus Spp.: Examining The Roles Of Environment, Evolution, And Genetics In Insect Mortality, Dana Blackburn

Theses and Dissertations

Entomopathogenic nematodes (EPNs) (genera Heterorhabditis and Steinernema) kill their invertebrate hosts with the aid of a mutualistic bacterium. The bacteria (Xenorhabdus spp. for steinernematids and Photorhabdus spp. for heterorhabditids) are primarily responsible for killing the host and providing the nematodes with nutrition and defense against secondary invaders. Photorhabdus is a Gram-negative bacterium in the Enterobacteriaceae family with high virulence towards their insect hosts. To achieve high mortality rates Photorhabdus produces a variety of virulence factors such as toxins, lipases, proteases, secretion systems, and fimbriae. EPNs are amenable to laboratory rearing and mass production for biocontrol applications against insects …

Genetic And Morphological Diversity Along Altitudinal Gradients In The Genus Rhoadsia (Teleostei: Characidae: Rhoadsiinae), Grace Malato

College of Science and Health Theses and Dissertations

The Neotropics have the highest fish species diversity of any area in the world, with some experts estimating that as many as 4000 species of fishes are present in freshwater ecosystems. Elevational gradients are partially responsible for this diversity due to the rapidly changing ecological conditions associated with changes in altitude in rivers. One area where elevational gradients are particularly important is Western Ecuador; this region forms part of a biodiversity hotspot extending south from Panama along the western side of the Andes. Fish species diversity is relatively low because of the small size of most of the river drainages …

Evolutionary Developmental Leaf Morphology Of The Plant Family Araceae, Claudia Liliana Henriquez

Arts & Sciences Electronic Theses and Dissertations

Studying the evolutionary developmental morphology of leaves using next-generation phylogenetics, a candidate gene approach and comparative developmental studies in the plant family Araceae is the overarching theme of the dissertation.

The plant family Araceae is an ancient lineage from the Early Cretaceous and belongs to the monocotyledons. Members of Araceae display striking variation in leaf development; such variation contradicts traditional models of monocot leaf development. Additionally, dissected leaves, which are rare in monocots, seem to have evolved independently multiple times in Araceae by various developmental mechanisms.

Despite extensive efforts to elucidate the evolutionary history of Araceae, phylogenetic ambiguity in the …

Peripheral And Central Mechanisms Of Temporal Pattern Recognition, Christa Ann Baker

Arts & Sciences Electronic Theses and Dissertations

Encoding information into the timing patterns of action potentials, or spikes, is a strategy used broadly in neural circuits. This type of coding scheme requires downstream neurons to be sensitive to the temporal patterns of presynaptic inputs. Indeed, neurons with temporal filtering properties have been found in a wide range of sensory pathways. However, how such response properties arise was previously not well understood. The goal of my dissertation research has been to elucidate how temporal filtering by single neurons contributes to the behavioral ability to recognize timing patterns in communication signals.

I have addressed this question using mormyrid weakly …

Evolutionary Convergence Of The Caffeine Biosynthetic Pathway In Chocolate Followed Duplication Of A Constrained Ancestral Enzyme, Andrew J. O'Donnell

Masters Theses

Caffeine biosynthesis is widely distributed in flowering plants and requires three consecutive methylation steps of xanthine alkaloids. Genes that have previously been reported to participate in the multi-step pathway in Coffea sp. (coffee) and Camellia sinensis (tea) encode members of the SABATH family of methyltransferases. Two genes highly expressed in fruits of Theobroma cacao (cacao) are orthologous to the caffeine genes in tea and appear to have diversified following gene duplication. Biochemical characterization of the enzymes (XMTs) encoded by these genes strongly suggest an unprecedented major pathway to theobromine, a precursor to caffeine. These findings imply that caffeine biosynthesis evolved …

Climate-Driven Change In Himalayan Rhododendron Phenology, Robert Evan Hart

Dissertations

Phenology – the seasonal timing of life-history events – is a critical dimension of natural history. It is also one of the earliest and most noticeable traits by which organisms respond to climate change. However, these responses are complex, and only beginning to be understood, especially in the montane and alpine environments that are among the ecosystems most vulnerable to climate change. Drawing from diverse data sets and employing multiple methodologies, I examined how climate affects phenology in Himalayan Rhododendron spp. Comprehensively monitoring flowering phenology over gradients of season and elevation on Mt. Yulong, China – home to a diverse …

The U1a/U2b"/Snf Family Of Rna Binding Proteins: Evolution Of Rna Binding Specificity And Contributions Of Heterotropic Linkage To Snrnp Protein Partitioning, Sandra Gisela Williams

Arts & Sciences Electronic Theses and Dissertations

The U1A/U2B"/SNF is a family of RNA binding proteins that is a highly conserved throughout eukaryotes. These proteins are found in the U1 and/or U2 splicing snRNPs (small nuclear ribonucleoprotein particles). In humans, U1A and U2B" specifically bind to the U1 and U2 snRNAs, respectively. The Drosophila genome codes for SNF, an essential protein that localizes to both the U1 and U2 snRNP. While a specific splicing functions for these proteins have not been determined, their conserved snRNP localization suggests an important splicing-related function.

The difference in protein number and partitioning between Drosophila and humans suggested that these proteins may …

Genetic Diversity, Population Structure, And Evolution Of Virulence In Toxoplasma Gondii, Elliot Keats Cullen Shwab

Doctoral Dissertations

Toxoplasma gondii is among the most widespread eukaryotic pathogens known. It chronically infects approximately one third of the world’s human population and has been isolated from an extremely diverse array of globally distributed mammals and birds. Understanding the structure of the worldwide T. gondii population enhances our understanding of the factors that have shaped that structure and led to the proliferation of one of the most evolutionarily successful pathogens on Earth. Herein we collate genotypic data from global isolates, demonstrating that T. gondii possesses a unique population structure in which only a small number of genotypes dominate throughout the northern …

The Evolution Of Body Size In The Order Siluriformes, D Cooper Campbell

Honors Theses

The evolution of body size has long been a topic of interest to biologists due to the close link between size and various aspects of an organism’s biology. Adult body size is influenced by the underlying tradeoff in energy allocation between maintenance, somatic growth and reproduction. I studied the evolution of a large group of globally distributed (primarily freshwater with some marine forms) fishes to test some basic hypotheses about the evolution of adult body size. Catfish (Siluriformes) are an excellent group for this type of research as they represent approximately 11% of fishes and species range in size from …

Population Genomic Inference Of Ecology, Conservation, Evolution, And Demographic History Of Atlantic Seahorses And Pipefishes (Syngnathidae), Joel Thomas Boehm

Dissertations, Theses, and Capstone Projects

In the Atlantic Ocean powerful directional ocean currents can play a significant role in the formation and persistence of marine species. Syngnathidae fishes have a sparse fossil record, high morphological plasticity, and many of these species are difficult to observe in the wild, therefore they frequently lack life history information and the status of regional lineages and species designations are often obscure. In this dissertation I explore the ecology, evolution, and conservation of primarily Atlantic seahorses (Hippocampus) and pipefish (Syngnathus) in four core chapters, using differing genetic datasets ranging from mitochondrial DNA to genome-wide RAD sequences. Most Synganthids have the …

Systematics And Biogeography Of Orthaea Kloztsch (Ericaceae: Vaccinieae), Nelson Salinas

Dissertations, Theses, and Capstone Projects

In the first chapter a study of the distribution patterns of the neotropical Vaccinieae (Ericaceae) is presented. Five areas of endemism were recovered: Central America, northern Chocó, southern Chocó, eastern Ecuador, and Yungas. Divergence times estimations indicate that the Andean clade of Vaccinieae migrated to South America during the Late Oligocene or Early Miocene (28.9-17.84 MA), and most of the subsequent diversification took place during the Tertiary. The Yungas was the first Andean area to be colonized, and several dispersals towards the north expanded their distribution range. Both areas of endemism and dispersal events were influenced by geological processes, such …

Experimental Evolution Of Specialism In A Wild Virus, Alexander Kula

Master's Theses

A pathogen's ability to successfully replicate and persist within a new host population is fraught with obstacles. While an expanded host-range allows for a greater chance at successful replication, such generalists are typically outcompeted by species which have specialized and adapted host-specific features. Although the most ubiquitous species on earth, very few bacteria-infecting viral species (bacteriophages) with truly broad host-ranges have been identified; this is partially due to the fact that only a small fraction of bacteria (and thus likely hosts) are amenable to laboratory conditions. Nevertheless, the processes of expanding as well as narrowing host-range are not well understood …

Mysteries Of The Trypanosomatid Maxicircles: Characterization Of The Maxicircle Genomes And The Evolution Of Rna Editing In The Order Kinetoplastida, Preethi Ranganathan Iyengar

Theses and Dissertations

The trypanosomatid protists belonging to Order Kinetoplastida are some of the most successful parasites ever known to mankind. Their extreme physiological diversity and adaptability to different environmental conditions and host systems make them some of the most widespread parasites, causing deadly diseases in humans and other vertebrates.

This project focuses on their unique mitochondrion, called the kinetoplast, and more specifically involves the characterization of a part of their mitochondrial DNA (also called kinetoplast DNA or kDNA), the maxicircles, which are functional homologs of eukaryotic mitochondrial DNA in the kinetoplastid protists. We have sequenced and characterized the maxicircle genomes of 20 …

Evolutionary Dynamics Of Speciation And Extinction, Dawn Michelle King

Doctoral Dissertations

Presented here is an interdisciplinary study that draws connections between the fields of physics, mathematics, and evolutionary biology. Importantly, as we move through the Anthropocene Epoch, where human-driven climate change threatens biodiversity, understanding how an evolving population responds to extinction stress could be key to saving endangered ecosystems. With a neutral, agent-based model that incorporates the main principles of Darwinian evolution, such as heritability, variability, and competition, the dynamics of speciation and extinction is investigated. The simulated organisms evolve according to the reaction-diffusion rules of the 2D directed percolation universality class. Offspring are generated according to one of three reproduction …

Human Feeding Biomechanics : Intraspecific Variation And Evolution, Justin Ledogar

Legacy Theses & Dissertations (2009 - 2024)

This study examines feeding biomechanics in modern human crania and those of extinct early members of the human lineage in order to better understand the selective pressures that influenced human craniofacial evolution. Specifically, this study uses finite element analysis to examine: 1) human feeding performance, in terms bite force production and craniofacial strength; 2) intraspecific variation in human feeding biomechanics; 3) feeding biomechanics in fossil hominins, including Australopithecus sediba and Homo habilis, species that are potentially at the root of modern human lineage, and 4) the functional role of purported facial buttresses.