Biology Commons^™

Guided Evolution To Expand The Host Range In Phages, Jamison Walker, Sandra Hope

Journal of Undergraduate Research

My project proposal included the use of Darwin’s theory of evolution by natural selection to determine if genetic mutations will arise in Bacteriophages that would allow them to infect related strains in a species of bacteria. Bacteriophages naturally have a target host range that they can infect. Within species of bacteria, the phage has tail receptors that allow it to infect specific strains. The other strains of the bacteria will be unaffected by the phage. In phage therapy, multiple phages with varied host ranges are chosen to combat this problem. Some phages are more effective than others in killing a …

Body Forms In Sharks (Chondrichthyes: Elasmobranchii), And Their Functional, Ecological, And Evolutionary Implications, Phillip C. Sternes

College of Science and Health Theses and Dissertations

Sharks are among the oldest vertebrate lineages in which their success has been attributed to their diversity in body shape and locomotor design. In this study, I investigated the diversity of body forms in extant sharks using landmark-based geometric morphometric analyses on lateral view illustrations of nearly all the known (ca. 470) extant sharks in a published guidebook. I ran three different analyses: the ‘full body,' ‘precaudal body,’ and ‘caudal fin' analyses. My study suggests that there are two basic body forms in sharks. The two major body forms are characterized as a ‘shallow-bodied’ form (Group A) and ‘deep-bodied’ form …

Reproductive Character Displacement In Calopteryx Aequabilis And C. Maculata: Improving Species Recognition Through The Divergence Of Male Mating Preferences, Melissa Encinias

Masters Theses, 2010-2019

An ongoing evolutionary question is how co-occurring species maintain reproductive barriers when they are morphologically, behaviorally, and ecologically similar. Without geographic isolation, traits involved in species recognition may be under selection to enhance reproductive barriers. Exaggerated trait differences between species in sympatric populations may reflect selection to reduce misdirected mating between species, or reproductive character displacement. While this phenomenon is widely recognized as an important stage in the speciation process, there is little direct evidence of this process in nature. In two North American damselfly species, Calopteryx aequabilis and C. maculata, wing pigmentation is sexually dimorphic and also shows …

Rapid Evolution Of Testis Size Relative To Sperm Morphology Suggests That Post-Copulatory Selection Targets Sperm Number In Anolis Lizards, A. F. Kahrl, Michele A. Johnson, R. M. Cox

Biology Faculty Research

Post-copulatory sexual selection is thought to be responsible for much of the extraordinary diversity in sperm morphology across metazoans. However, the extent to which post-copulatory selection targets sperm morphology versus sperm production is generally unknown. To address this issue, we simultaneously characterized the evolution of sperm morphology (length of the sperm head, midpiece and flagellum) and testis size (a proxy for sperm production) across 26 species of Anolis lizards, a group in which sperm competition is likely. We found that the length of the sperm midpiece has evolved 2–3 times faster than that of the sperm head or flagellum, suggesting …

A Phylogenetic Analysis Of Bostrichoidea (Coleoptera) And Revisions Of The Southern African Spider Beetle Genera Meziomorphum And Eutaphroptinus (Ptinidae: Coleoptera), Olivia M. Gearner

Masters Theses & Specialist Projects

Proposals for the internal relationships and classification of the bostrichoids are currently poorly supported, and almost all are based on morphology alone. This study improves upon on previous phylogenetic analyses of the group by including more taxa using the standard genes for many phylogenetic analyses. Cytochrome C oxidase subunit 1 (CO1), 28S small subunit rRNA, and 16S small subunit rRNA mitochondrial genes were sequenced or obtained from Genbank, then analyzed using parsimony and Bayesian analyses. Topologies differed depending on genes used. A three gene tree and a two gene (28S and CO1) tree both supported relationships in which a basal …

Multispecies Character Displacement In Mexican Poeciliopsis Fishes, Andrea J. Roth

Theses and Dissertations

Competition has long been recognized as a central force in shaping evolution, particularly through character displacement. Yet research on character displacement is biased as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Unfortunately, communities are seldom so simple that only pairs of species interact, and it is not clear if inferences from pairwise interactions are sufficient to explain patterns in nature. A more realistic approach is to ask how traits evolve when multiple species interact. Here I explore the importance of multispecies competitive interactions on trait evolution in four congeneric species of livebearing fishes …

Plant Mitochondrial Genome Evolution And Structure Has Been Shaped By Double-Strand Break Repair And Recombination, Emily Wynn

School of Biological Sciences: Dissertations, Theses, and Student Research

Plant mitochondrial genomes are large but contain a small number of genes. These genes have very low mutation rates, but genomes rearrange and expand at significant rates. We propose that much of the apparent complexity of plant mitochondrial genomes can be explained by the interactions of double-strand break repair, recombination, and selection. One possible explanation for the disparity between the low mutation rates of genes and the high divergence of non-genes is that synonymous mutations in genes are not truly neutral. In some species, rps14 has been duplicated in the nucleus, allowing the mitochondrial copy to become a pseudogene. By …

Phylogeography Of The Neotropical Fish Genus Rhoadsia (Teleostei: Characidae) In Ecuador, Roberto Valentino Cucalón Tamayo

College of Science and Health Theses and Dissertations

Western Ecuador is considered a biodiversity hotspot. Nevertheless, studies of population genetic structure and variation are rare, especially in aquatic species. The genus Rhoadsia is an endemic freshwater fish in this region with two recognized species, Rhoadsia minor and R. altipinna. Little is known about the evolutionary relationships of their populations, and due to morphological similarities, their validity as distinct species has been questioned. The present study uses a phylogeographic approach to examine the evolutionary history of the genus and the validity of the two described species. Furthermore, I investigated the possible geographical origin of the genus based on patterns …

Complex Gene Loss And Duplication Events Have Facilitated The Evolution Of Multiple Loricrin Genes In Diverse Bird Species, Anthony C. Davis, Matthew J. Greenwold, Roger H. Sawyer

Faculty Publications

The evolution of a mechanically resilient epidermis was a key adaptation in the transition of amniotes to a fully terrestrial lifestyle. Skin appendages usually form via a specialized type of programmed cell death known as cornification which is characterized by the formation of an insoluble cornified envelope (CE). Many of the substrates of cornification are encoded by linked genes located at a conserved genetic locus known as the epidermal differentiation complex (EDC). Loricrin is the main protein component of the mammalian CE and is encoded for by a gene located within the EDC. Recently, genes resembling mammalian loricrin, along with …

The Nature Of Science As A Foundation For Fostering A Better Understanding Of Evolution, Craig E. Nelson, Lawrence C. Scharmann, Jean Beard, Lawrence I. Flammer

Department of Teaching, Learning, and Teacher Education: Faculty Publications

Misunderstandings of the nature of science (NOS) contribute greatly to resistance to evolutionary theory especially among non-scientific audiences. Here we delineate three extended instructional examples that make extensive use of NOS to establish a foundation upon which to more successfully introduce evolution. Specifically, these instructional examples enable students to consider evolutionary biology using NOS as a lens for interpretation of evolutionary concepts. We have further found, through our respective research efforts and instructional experiences, that a deep understanding of NOS helps students understand and accept the scientific validity of evolution and, conversely, that evolution provides an especially effective context for …

A Chromosome-Scale Assembly Of The Axolotl Genome, Jeramiah J. Smith, Nataliya Y. Timoshevskaya, Vladimir A. Timoshevskiy, Melissa C. Keinath, Drew Hardy, S. Randal Voss

Biology Faculty Publications

The axolotl (Ambystoma mexicanum) provides critical models for studying regeneration, evolution, and development. However, its large genome (∼32 Gb) presents a formidable barrier to genetic analyses. Recent efforts have yielded genome assemblies consisting of thousands of unordered scaffolds that resolve gene structures, but do not yet permit large-scale analyses of genome structure and function. We adapted an established mapping approach to leverage dense SNP typing information and for the first time assemble the axolotl genome into 14 chromosomes. Moreover, we used fluorescence in situ hybridization to verify the structure of these 14 scaffolds and assign each to its …

Exposure To Environmental Radionuclides Associates With Tissue-Specific Impacts On Telomerase Expression And Telomere Length, Jenni Kesaniemi, Anton Lavrinienko, Eugene Tukalenko, Zbyszek Boratynski, Kati Kivisaari, Tapio Mappes, Gennadi Milinevsky, Anders Pape Moller, Timothy A. Mousseau, Phillip C. Watts

Faculty Publications

Telomeres, the protective structures at the ends of chromosomes, can be shortened when individuals are exposed to stress. In some species, the enzyme telomerase is expressed in adult somatic tissues, and potentially protects or lengthens telomeres. Telomeres can be damaged by ionizing radiation and oxidative stress, although the effect of chronic exposure to elevated levels of radiation on telomere maintenance is unknown for natural populations. We quantified telomerase expression and telomere length (TL) in different tissues of the bank vole Myodes glareolus, collected from the Chernobyl Exclusion Zone, an environment heterogeneously contaminated with radionuclides, and from uncontaminated control sites …

Concept Inventories As A Resource For Teaching Evolution, Robert E. Furrow, Jeremy L. Hsu

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Understanding evolution is critical to learning biology, but few college instructors take advantage of the body of peer-reviewed literature that can inform evolution teaching and assessment. Here we summarize the peer-reviewed papers on tools to assess student learning of evolutionary concepts. These published concept inventories provide a resource for instructors to design courses, gauge student preparation, identify key misconceptions in their student population, and measure the impact of a lesson, course, or broader curriculum on student learning. Because these inventories vary in their format, target audience, and degree of validation, we outline and explain these features. In addition to summarizing …

Repeats Of Unusual Size In Plant Mitochondrial Genomes: Identification, Incidence And Evolution, Emily L. Wynn, Alan C. Christensen

School of Biological Sciences: Faculty Publications

Plant mitochondrial genomes have excessive size relative to coding capacity, a low mutation rate in genes and a high rearrangement rate. They also have abundant non-tandem repeats often including pairs of large repeats which cause isomerization of the genome by recombination, and numerous repeats of up to several hundred base pairs that recombine only when the genome is stressed by DNA damaging agents or mutations in DNA repair pathway genes. Early work on mitochondrial genomes led to the suggestion that repeats in the size range from several hundred to a few thousand base pair are underrepresented. The repeats themselves are …

Long-Term Experimental Hybridisation Results In The Evolution Of A New Sex Chromosome In Swordtail Fish, Paolo Franchini, Julia C. Jones, Peiwen Xiong, Susanne Kneitz, Zachariah Gompert, Wesley C. Warren, Ronald B. Walter, Axel Meyer, Manfred Schartl

Biology Faculty Publications

The remarkable diversity of sex determination mechanisms known in fish may be fuelled by exceptionally high rates of sex chromosome turnovers or transitions. However, the evolutionary causes and genomic mechanisms underlying this variation and instability are yet to be understood. Here we report on an over 30-year evolutionary experiment in which we tested the genomic consequences of hybridisation and selection between two Xiphophorus fish species with different sex chromosome systems. We find that introgression and imposing selection for pigmentation phenotypes results in the retention of an unexpectedly large maternally derived genomic region. During the hybridisation process, the sex-determining region of …

Contemporaneous Radiations Of Fungi And Plants Linked To Symbiosis, François Lutzoni, Michael D. Nowak, Michael E. Alfaro, Valérie Reeb, Jolanta Miadlikowska, Michael Krug, A. Elizabeth Arnold, Louise A. Lewis, David L. Swofford, David Hibbett, Khidir Hilu, Timothy Y. James, Dietmar Quandt, Susana Magallón

Biology

Interactions between fungi and plants, including parasitism, mutualism, and saprotrophy, have been invoked as key to their respective macroevolutionary success. Here we evaluate the origins of plant-fungal symbioses and saprotrophy using a time-calibrated phylogenetic framework that reveals linked and drastic shifts in diversification rates of each kingdom. Fungal colonization of land was associated with at least two origins of terrestrial green algae and preceded embryophytes (as evidenced by losses of fungal flagellum, ca. 720 Ma), likely facilitating terrestriality through endomycorrhizal and possibly endophytic symbioses. The largest radiation of fungi (Leotiomyceta), the origin of arbuscular mycorrhizae, and the diversification of extant …

Effects Of Evolution On Laboratory Sublines Of Myxococcus Xanthus Dk1622, Mackenzie Ryan, Francesca Scribano, Kimberly Murphy

Celebration of Learning

Microbes have served as effective models for studying evolution because of their ability to be easily replicated, stored, and manipulated. Myxococcus xanthus is a soil bacterium that has served as a model organism in many laboratories. The unique social and motile behaviors exhibited by this bacterium make it ideal for phenotypic assays. A wild-type strain of M. xanthus, DK1622, has been distributed to laboratories across the United States and therefore we now have DK1622 sublines. The genomes of a number of these sublines have been sequenced and their social and motile phenotypes have been analyzed. When nine of these sublines …

Achilles And The Tortoise: Some Caveats To Mathematical Modeling In Biology, Scott F. Gilbert

Biology Faculty Works

Mathematical modeling has recently become a much-lauded enterprise, and many funding agencies seek to prioritize this endeavor. However, there are certain dangers associated with mathematical modeling, and knowledge of these pitfalls should also be part of a biologist's training in this set of techniques. (1) Mathematical models are limited by known science; (2) Mathematical models can tell what can happen, but not what did happen; (3) A model does not have to conform to reality, even if it is logically consistent; (4) Models abstract from reality, and sometimes what they eliminate is critically important; (5) Mathematics can present a Platonic …

Using Snake Genomes To Illuminate The Patterns And Mechanisms Of Rapid Adaptation, Daren Carter Card

Biology Dissertations - Archive

One of the most important and interesting goals in evolutionary biology is to understand the mechanisms generating biodiversity and adaptive novelty. Ever-evolving genomic techniques have served as a catalyst for this work, enabling rapid increases in our knowledge of diverse taxa. By leveraging a combination of phylogeographic, population genetic, and comparative genomic methods, I established two snake systems with unique attributes that showed promise for increasing our understanding of important evolutionary questions related to local adaptation and convergence. Using sampling from several island populations of Boa imperator with similar adaptive phenotypes (e.g., reduced body size and craniofacial morphological shifts), I …

The Effect Of An Historical Geology Course On Students’ Attitudes Towards Science And Their Knowledge Of Deep Time As A Threshold To Their Knowledge Of Evolution, Allan Nolan

Dissertations

In America there exists a conflict between a small group of its citizens and the concept of evolution. Researchers have studied this conflict and the ways in which teachers might approach educational methodologies that not only address evolution in a sensitive manner, but also remain legally acceptable.

This research was designed to address teaching evolution in the context of deep time – the concept that time is vast and that geology and biology operate in a timescale of hundreds of millions to billions of years. In previous peer-reviewed works, it has been stated that deep time acts as a threshold …

Investigations On The Role Of The Immune System In Mammary Development And Maternal Immunity In The Marsupial, Monodelphis Domestica, Bethaney D. Fehrenkamp

Biology ETDs

All newborn mammals are highly dependent upon milk for nourishment and immune protection. This is especially true for marsupials, a lineage of mammals with a short gestation, limited placental development, and an increased reliance on an extended lactation period. Most newborn marsupials do not receive passive maternal immunity in utero and therefore are entirely dependent upon factors within the milk for immune protection until capable of mounting their own response. In this project we seek to characterize the complex lactation program utilized by marsupials, and seek greater understanding of the maternal role in the establishment of the developing immune system …

Digging Biomechanics In Geomyoid Rodents, Alexis Moore Crisp

UNLV Theses, Dissertations, Professional Papers, and Capstones

Subterranean digging behaviors provide opportunities for protection, access to prey, and predator avoidance for a diverse array of vertebrates, yet studies of the biomechanics of burrowing have been limited by the technical challenges of measuring kinetics and kinematics of animals moving within a substrate. Prior studies of burrowing have recorded a single axis of x-ray video and/or force. However, empirical observations show that burrowing is not restricted to a single axis or plane. I describe a new system called a ‘tunnel-tube’ for measuring 3D reaction force during burrowing. This tunnel-tube has two separate tubes, one ‘entry tube’ that has no …

Evolution Of Voltage-Gated Ion Channels, Kevin Gregory Bennett, Kevin Bennett

Master of Science in Integrative Biology Theses

Voltage-gated Ion Channels (VICs) form a superfamily of energy-independent membrane transporters that facilitate the transfer of charged sodium, calcium, and potassium ions across the cell membrane (Hodgkin & Huxley 1952). The channels contain a selective ion-conducting pore along with several other structural and gating features that come together to form a functional hetero- or homotetramer. A comprehensive phylogenetic study of all available proteins aimed at finding unknown distribution and illuminating evolutionary paths would be immensely useful in understanding relationships of structure, function, and organismal distribution. This phylogenetic analysis of VICs will be immensely useful in characterizing functional and structural distribution, …

Hormonebase, A Population-Level Database Of Steroid Hormone Levels Across Vertebrates, Maren N. Vitousek, Michele A. Johnson, Jeremy W. Donald, C. D. Francis, M. J. Fuxjager, W. Goymann, M. Hau, Jerry F. Husak, Bonnie K. Kircher, R. Knapp, L. B. Martin, E. T. Miller, L. A. Schoenle, J. J. Uehling, T. D. Williams

Biology Faculty Research

Hormones are central regulators of organismal function and flexibility that mediate a diversity of phenotypic traits from early development through senescence. Yet despite these important roles, basic questions about how and why hormone systems vary within and across species remain unanswered. Here we describe HormoneBase, a database of circulating steroid hormone levels and their variation across vertebrates. This database aims to provide all available data on the mean, variation, and range of plasma glucocorticoids (both baseline and stress-induced) and androgens in free-living and un-manipulated adult vertebrates. HormoneBase (www.HormoneBase.org) currently includes >6,580 entries from 476 species, reported in 648 publications from …

Rattlesnake Genomics Illustrate Patterns Of Speciation, Adaptation, And Links Between Genome Structure And Function, Drew Roberts Schield

Biology Dissertations - Archive

Understanding the origins of species and biological novelties that allow them to thrive in diverse environments is a key goal in evolutionary biology, and new genomic methods are constantly enabling research using non-model species to address important questions related to speciation and adaptation. Using phylogeographic, population genetic, and comparative genomic methods, I demonstrate that North American rattlesnakes are a uniquely enriched system for investigating patterns and processes at the intersection of adaptation and speciation. Specifically, this dissertation explores the evolution of biological novelty at multiple scales, including the origins of reproductive incompatibilities during the process of gene flow in secondary …

Sequencing And Analysis Of Centromere Protein B In Wallaby And The Rapid Evolution Of The Centromere, Alexander Tedeschi

Honors Scholar Theses

Using a combination of Sanger sequencing and RNA-seq data, this project aims to determine the nucleotide and amino acid sequence of Centromere Protein B (CENP-B), an important protein involved in the assembly of the kinetochore protein complex at the centromere, in several species of marsupials, specifically wallabies. Despite their recent evolutionary history, these species have been shown to have surprisingly divergent centromeric DNA sequences. Through comparative analysis of these sequences, this project, along with analysis of several other CENPs, aims to determine if this divergence extends to the proteins closely associated with these sequences and possibly even further into the …

The Evolutionary Significance Of Body Size In Burying Beetles, Ashlee Nichole Momcilovich

Theses and Dissertations

Body size is one of the most commonly studied traits of an organism, which is largely due to its direct correlation with fitness, life history strategy, and physiology of the organism. Patterns of body size distribution are also often studied. The distribution of body size within species is looked at for suggestions of differential mating strategies or niche variation among ontogenetic development. Patterns are also examined among species to determine the effects of competition, environmental factors, and phylogenetic inertia. Finally, the distribution of body size across the geographic range of a species or group of closely related is looked at …

Evolution Of Alu Elements In The Saimiri And Papio Lineages Of Primates, Jasmine Nicole Brown Baker

LSU Doctoral Dissertations

Alu elements are approximately 300 base pair (bp) primate specific non- autonomous retrotransposons. Alu elements, a short interspersed element (SINE), account for high copy numbers in all primate genomes. Numerous Alu element subfamilies have undergone varying degrees of activity and amplification within primates. Identification of these subfamilies has proved to be very informative in elucidating phylogenies and as phylogenomic markers. Squirrel monkeys, genus Saimiri, are one of the most well-known neotropical primates and the second most commonly used laboratory monkey. Squirrel monkey species diverged approximately 1.5 million years ago and are native to South America. Despite being well-known, there …

A Biogeographic Perspective On The Evolution Of Fire Syndromes In Pine Trees (Pinus: Pinaceae), Kevin J. Badik, Joshua P. Jahner, Joseph S. Wilson

Biology Faculty Publications

Our goals were to explore the relationship between biogeography and the evolution of fire-adaptive syndromes in the genus Pinus. We used a previously published time-calibrated phylogeny and conducted ancestral trait reconstruction to estimate the likely timing of diversification in Pinus, and to determine when fire-adaptive syndromes evolved in the lineage. To explore trait conservation among fire syndromes and to investigate historical biogeography, we constructed ancestral state reconstructions using the program RASP and estimated the degree of conservatism for fire-adapted traits in the program BaTS. Our reconstructions suggest that the Bering land bridge, which connected North America and Asia, probably played …

Does Body Size Affect Fitness The Same Way In Males And Females? A Test Of Multiple Fitness Components, Ashlee N. Smith, Mark C. Belk

Faculty Publications

Body size generally has an important relationship with fitness, whereby larger body size leads to an increase in fitness through competition, reproductive output and survivorship. However, the traits through which body size increases fitness often differ between the sexes. We tested for the effects of body size on fitness in both sexes using three separate experiments on competitive ability, reproductive output and starvation resistance in the burying beetle Nicrophorus marginatus. Results varied between sexes as follows: (1) larger body size increased competitive ability differentially between sexes; (2) female body size, but not male body size, significantly affected reproductive output …