Browsing by Subject "Evolution"

Now showing 1 - 17 of 17

Anatomy, Systematics, and Evolution of Catarrhines from the Late Oligocene and Early Miocene of Eastern Africa
(2019-10) Jansma, Rutger
The early Miocene catarrhines are key taxa for elucidating the evolutionary history of the Hominoidea and Cercopithecoidea because they are temporally and morphologically intermediate between more primitive Oligocene faunas and modern primate communities. However, insight into the adaptive processes that led to the living catarrhine clades is obscured because of confusion over both taxonomic diversity and systematic affinities within key early Miocene groups. The research presented in this dissertation takes advantage of the increase in new, more complete fossils and taxa to overcome these limitations. The small catarrhines and nyanzapithecines are revised following a comprehensive review, resulting in the description of two new genera (Gen. nov. A and Gen. nov. B), a new species of Dendropithecus, and transfer of Nyanzapithecus harrisoni to Turkanapithecus. This revision provides evidence for increased geographic and ecological differentiation among sympatric small catarrhines, nyanzapithecines, and large-bodied hominoids during the early Miocene. A new phylogenetic analysis using maximum parsimony includes 64 taxa and 243 characters, and recovered a well-resolved consensus tree (MPTs = 18, 901 steps long) that supports monophyly of Cercopithecoidea and Hominoidea. Within Hominoidea, the Pliopithecidae, Dendropithecidae, and Proconsulidae are identified as successively more derived monophyletic clades. A monophyletic Oreopithecidae clade containing Oreopithecus and the nyanzapithecines is also well supported within Hominoidea. However, the positions of Pliopithecidae and Oreopithecidae are strongly influenced by the morphology preserved within single species in these clades. This demonstrates both the importance of comprehensive taxonomic sampling and the impact of missing data on phylogenetic results. The analysis also reveals that suspensory adaptations documented in living apes appeared independently in four hominoid clades (Pliopithecidae, Oreopithecidae, Hylobatidae, and Hominidae). This result is realized through the large taxon sampling in the analysis and demonstrate that the homoplastic character states in these taxa are expressed differently among clades. Finally, a general perspective on catarrhine evolution emphasizes that the appearance of the ancestral hominin cannot be properly interpreted without making reference to the entire Miocene ape radiation.
B3GET: A new computational approach for understanding and exploring ecology, evolution, and behavior
(2021-12) Crouse, Kristin
Biological anthropologists seek to understand the origin and evolution of distinctively human traits, including language, cumulative culture, and intensely cooperative societies. To understand the evolution of human behavior, we need a viable theory of socioecology. Studies of our primate relatives provide opportunities to develop and test socioecological models which can in turn help explain the evolution of human behavior. However, it has become increasingly clear that current socioecological models do not fully explain primate social behavior. Among many important limiting factors are the sheer number of variables to track and the difficulty of operationalizing ecological concepts such that they can be measured feasibly in the field. Microscale (i.e., agent-based) models have great potential for advancing the field because they can handle many different variables and incorporate individual variation, stochasticity, and emergent properties. I reviewed the existing literature on microscale models in behavioral ecology to better understand the state-of-the-art for models relevant to primate socioecology. I found that models are often designed for a single species or single area of research, limiting their application to broader questions. Many models also do not consider important biological constraints such as spatial relationships or rules for birth and death that depend on individual characteristics, nor are they often validated for accuracy. As a contribution towards a more complete understanding of primate socioecology, I developed B3GET, a microscale model that incorporates important biological constraints and can track key socioecological variables in simulated primates. These virtual primates possess decision-making rules encoded in simulated diploid chromosomes, which dictate movement, body growth, inclination to mate, eat, and other behaviors. I developed these rules based on primate socioecological data from the literature and my own field observations. The virtual primate environment consists of a landscape of plants that can vary in their quality and distribution. B3GET users can edit the starting genotype and population files to create different virtual populations with different behaviors, and then collect simulation data for hypothesis testing. I simulated four primate species – chimpanzees, geladas, hamadryas baboons, and olive baboons – and showed that these simulated species display typical real-life behaviors in their group composition, dispersal patterns, and mating strategies. I built upon recent model-validation frameworks to analyze B3GET using a series of tests. Some important findings include: Hamilton's rule emerged under some, but not all, simulation conditions; individuals appeared to have the highest fitness in medium-sized groups; and spatial relationships do matter: primates living in aspatial simulations committed infanticide 10 times more frequently than identical primates in spatial simulations. Because B3GET can viably simulate other primate species, it is a promising approach for investigating the origins of distinctively human behaviors.
Change and reliability in the evolution of learning and memory.
(2009-05) Dunlap-Lehtilä, Aimee Sue
Why do animals learn to perform some behaviors while others are innate? Why do animals learn some things more easily than others? And, why do animals remember some things better than others? Theoreticians argue that patterns of environmental change explain these patterns, but we have little data to support these claims. I used statistical decision theory to model behaviors and fitness consequences, and experimental evolution studies with fruit flies where I manipulated patterns of environmental change across evolutionary time, to address the first two of these fundamental questions about the evolution of learning. The first experiment tested the effects of the reliability of experience and the fixity of the best action upon the evolution of learning and non-learning across 30 generations. I found that indeed, the interaction of these two variables determined when learning, and when non-learning evolved. The second study was a full factorial experiment manipulating the reliabilities of two modes of stimuli: olfactory and visual. After 40 generations, I found that as predicted, flies in environments where olfactory stimuli are reliable learned better about olfactory than color stimuli, with the same being true for color stimuli. Finally, I addressed the question of why animals remember some things better than others using a dynamic programming technique and experiment with blue jays, finding interactions between rates of change and time. These novel studies show the importance of reliability and change in evolution of learning and memory.
Characterization and evolution of artificial RNA ligases
(2015-06) Morelli, Aleardo
Enzymes enable biocatalysis with minimal by-products, high regio- and enantioselectivity, and can operate under mild conditions. These properties facilitate numerous applications of enzymes in both industry and research. Great progress has been made in protein engineering to modify properties such as stability and catalytic activity of an enzyme to suit specific processes. On the contrary, the generation of artificial enzymes de novo is still challenging, and only few examples have been reported. The study and characterization of artificial enzymes will not only expand our knowledge of protein chemistry and catalysis, but ultimately improve our ability to generate novel biocatalysts and engineer those found in nature. My thesis focused on the characterization of an artificial RNA ligase previously selected from a library of polypeptide variants based on a non-catalytic protein scaffold. The selection employed mRNA display, a technique to isolate de novo enzymes in vitro from large libraries of 1013 protein variants. The artificial RNA ligase catalyzes the formation of a phosphodiester bond between two RNA substrates by joining a 5'-triphospate to a 3'-hydroxyl, with the release of pyrophosphate. This activity has not been observed in nature. An initial selection carried out at 23°C yielded variants that were poorly suitable for biochemical and biophysical characterization due do their low solubility and poor folding. We hence focused our studies on a particular improved ligase variant called ligase 10C, isolated from a subsequent selection performed at 65°C. Here we report the structural and biochemical characterization of ligase 10C. We solved the three-dimensional structure of this enzyme by NMR. Unexpectedly, the original structure of the parent scaffold used for building the original library was abandoned. The enzyme instead adopted a novel dynamic fold, not previously observed in nature. The structure was stabilized by metal coordination, yet lacked secondary structural motifs entirely. We also compared the catalytic and thermodynamic properties of ligase 10C to enzyme variants previously selected at lower temperature (23°C). Ligase 10C displayed a remarkable increase in melting temperature of 35°C compared to its mesophilic counterpart. In addition, its activity at 23°C was about 10-fold higher compared to the mesophilic variants. This work was the first mRNA display selection for catalytic activity at high temperature, and further highlighted the capacity of the technique to select for proteins with rare properties. To facilitate detailed mechanistic studies of this unnatural enzyme, a crystal structure would be essential. Unfortunately, ligase 10C did not form crystals likely due to its highly dynamic regions. With the goal of identifying a truncated less flexible version of the enzyme that would be more suited for crystallization, we generated a library of random deletion variants of ligase 10C and performed an mRNA display selection to identify shorter active variants. Finally, we describe the attempted selection of an enzyme for the same RNA ligation reaction from a completely random polypeptide library. The long-term goal of the overarching project in the Seelig lab is to elucidate and compare the structure and mechanism of enzymes generated from different starting points, yet catalyzing the same reaction, to obtain insights into potential evolutionary pathways. In summary, our work revealed the unusual structural and biophysical properties of the artificial ligase 10C, and thereby demonstrated the power and flexibility of mRNA display as a technique for the selection of de novo enzymes.
Conceptual Modeling of Adaptive Therapy Dosing for Chemotherapeutic Administration in Cancer Allows for the Direct Comparison of Continuous and Adaptive Dosing Regimes
(2022-05) McGehee, Cordelia
Adaptive therapy of cytotoxic (cell killing) chemotherapy has been proposed as a method to prolong progression-free survival in certain cancers when underlying cell-cell competition between sensitive and resistant cancer cells is present. Traditionally, cytotoxic chemotherapy dosing is administered at the maximal tolerated dose with the goal of rapidly shrinking tumor growth. In the case of a tumor where underlying intratumoral cell-cell competition between a drug sensitive and drug resistant population leads to competition for resources, it is hypothesized that maximally killing the sensitive cell population allows for competitive release of the resistant cell population and outgrowth of a chemotherapy resistant tumor. In adaptive therapy, chemotherapy is administered when a tumor reaches a certain upper threshold and then is discontinued when the tumor shrinks to a specified lower threshold. The purpose of this strategy is to use the sensitive cell population to inhibit the growth of the resistant cell population and increase the length of time to competitive release and outgrowth of the resistant cell population. In this thesis, a modified Lotka-Volterra competition model is explored across competition parameters in order to analytically address 1) the optimality of continuous fixed dose versus adaptive dosing schedules and 2) the role of drug dose and mechanism of action in the choice of dosing regime. Using this model, several novel results are shown. First, for certain parameters, complete tumor eradication can be achieved in the presence of a resistant subpopulation under adaptive cytotoxic or continuous antiproliferative (decreasing growth rate) dosing schedules. Second, in this parameter space, fixed dose antiproliferative dosing schedules are more robust than cytotoxic adaptive regimes to uncertainty in initial conditions. Third, in parameter spaces where eradication of the resistant cell population is not feasible, both fixed dose antiproliferative schedules and cytotoxic adaptive therapy schedules may result in delayed resistant cell outgrowth over maximum tolerated dose and are comparable in their benefits. Overall, these results indicate that both antiproliferative continuous fixed dose therapy and cytotoxic adap-tive therapy can be used for tumor management in the case of underlying intratumoral competition between chemotherapy sensitive and chemotherapy resistant cells.
Developing methods to understand and engineer protease cleavage specificity
(2016-09) Lane, Michael
Proteases are ubiquitous enzymes that comprise nearly 2% of all human genes. These robust enzymes are attractive potential therapeutics due to their catalytic turnover and capability for exquisite specificity. While most existing drugs require a stoichiometric ratio to function, therapeutic proteases could clear their targets much more efficiently. Unfortunately, existing technologies are inadequate for understanding and engineering therapeutic proteolytic specificities. My thesis work has focused on building the groundwork to enable these technologies to thrive. For the goal of engineering a new protease, it is currently necessary to identify prototype proteases for engineering efforts that have specificities similar to the desired target substrate. Current technologies are unable to characterize proteases adequately for this goal. Accordingly, I invested in developing a method for the accurate characterization of protease cleavage specificity. Our unique combination of mRNA display technology, Next-Generation Sequencing, and mass spectrometry enables the sampling of all possible permutations of octamer substrates and the identification of millions of cleavage sites. The throughput of our approach is orders of magnitude greater than the current state-of-the-art methods. The resulting high-resolution specificity maps can be applied to identify promising protease prototypes, predict human cross-reactivity, or lead to a better understanding of this critical component of natural physiology. In the work presented here, I applied my new specificity-screening method to assess the specificities of the proteases factor Xa, ADAM17, and streptopain. The resulting cleavage preference maps confirmed known specificities, and revealed new insight into the broad preferences of both narrow- and broad-specificity proteases. In particular, disfavored amino acids were illuminated better than ever before. The next focus of my work was to engineer multiple-subsite novel protease specificity. I chose streptopain as the prototype for my efforts to neutralize the superantigen exotoxin SpeA. I identified a target loop of SpeA wherein cleavage would result in inactive fragments. Further, I confirmed that streptopain can be successfully presented as an mRNA displayed fusion. In summary, my thesis work established crucial methodologies for applying mRNA display technology to enable the understanding and ultimately engineering the specificity of therapeutic proteases.
Developing new enzymatic catalysts by resurrecting ancestral alpha/beta hydrolases
(2014-09) Mooney, Joanna Lynn
In our daily lives, we use items created by synthetic chemistry. In some cases, traditional chemical synthesis of these items requires harsh solvents, extreme temperatures, and results in large amounts of waste generated by side reactions. Developing enzymatic catalysts is a possible solution to this problem because enzymes are more selective, easy to dispose of, and react at ambient conditions. Modern day specialist enzymes are thought to have evolved from ancient generalists that catalyzed several reactions promiscuously. Our lab has reconstructed a number of ancestral enzymes from extant members of the alpha/beta hydrolase family. We have screened these enzymes for promiscuous reaction and substrate activities. The aldol and nitroaldol reactions are very important for the catalysis of many pharmaceuticals and commodity chemicals. One of our reconstructed ancestral enzymes catalyzes a nitroaldol reaction at a higher rate than modern day enzymes. We have also identified what is potentially a partial aldol reaction.
The ecology and evolution of an invasive perennial plant (Lythrum salicaria) in the context of biological control by specialist herbivores (Galerucella spp.)
(2013-09) Quiram, Gina Louise
The introduction of non-native species to novel ranges has provided biologists the opportunity to study organisms experiencing sudden and sustained shifts in community composition and selection pressure. Management programs for invasive species can result in similar shifts. In classical biological control programs, non-native species are introduced to control invasive species. The short-term impacts of these introductions on invaded communities are often well documented, but the long-term impacts on the ecology and evolution of target invasive species are not well understood. Using a combination of field surveys, common garden techniques, and quantitative genetic models, I examined the effect of biological control by specialist herbivores (Galerucella spp.) on purple loosestrife (Lythrum salicaria L.) in southern Minnesota (MN), USA. Chapter 1 describes field surveys completed to determine the extent to which biological control directly reduces plant vigor, competitive performance, and reproduction. In Chapter 2, I quantify the extent to which population level variation in vigor, competitive performance, herbivore defense, and herbivore tolerance of L. salicaria reflects an evolutionary divergence following the introduction of biological agents. Finally, in Chapter 3 I assess the potential for L. salicaria to evolve in response to continued selection pressure. The results of these studies show that Galerucella spp. biocontrol agents remain established and continue to feed on L. salicaria in southern MN, but do not universally reduce the vigor, competitive performance, or reproduction of the plant in field populations as compared to populations lacking established populations of biocontrol agents. When grown in a common environment, an experimental garden, populations of L. salicaria having experienced herbivory by Galerucella spp. for 16 years are more vigorous, marginally more competitive, and marginally more tolerant of herbivory compared to populations lacking a historical association with the herbivore. In MN, L. salicaria is currently under selection pressure for increased vigor, and the plant has the genetic capacity to adapt in response to this selection pressure. Further evolution of L. salicaria could decrease the effectiveness of biological control by Galerucella spp.
Entangled Influence: Wordsworth and Darwinism in the Late Victorian Period
(2014-07) Olsen, Trenton B.
This dissertation examines the intersection of William Wordsworth's influence and evolutionary theory---the nineteenth century's two defining representations of nature---in late Victorian literature and society. Victorian writers were sensitive to the compatibilities and conflicts between these philosophies, and Wordsworth's poetry was enlisted in arguments both for and against evolution. Creative writers and critics alike turned to the poet as an alternative or antidote to evolution, criticized and revised his poetry in response to this discourse, and synthesized elements of each to propose their own modified theories. In engaging with Wordsworth's influence in this way, these writers began to see literary influence and history in Darwinian terms. They viewed their engagement with Wordsworth and Darwin, which was both competitive and collaborative, as a struggle for literary survival and offspring as well as transformative encounters in their development. This model of "literary selection" synthesizes opposing influence theories, and differs from objectivist accounts of Darwinian cultural transmission through its emphasis on writers' subjectivities, idiosyncratic language, and conscious adoption and modification of evolutionary ideas in their literary relationships. The opening chapter surveys a broad range of critical and creative writing to demonstrate the prevalence of Wordsworth's and Darwin's intertwining influences in the period, and outlines the various ideological positions late Victorian writers occupied toward these entangled philosophies. The chapter explores these simultaneous influences in the work of Thomas Hardy, George Meredith, Gerard Manley Hopkins, Charles Kingsley, and Emily Pfieffer along with a host of Victorian critics. The three central chapters provide in-depth demonstrations of this argument in the work of Matthew Arnold, George Eliot, and Robert Louis Stevenson, respectively. The final chapter moves beyond literature to read the late nineteenth-century conservation movement, in which The Wordsworth Society helped establish the National Trust to preserve the Lake District's landscape, as a conflict between Wordsworthian and Darwinian ideas.
Evolutionary impacts of assisted gene flow: Fitness consequences of hybridization along a geo-climatic gradient in an annual prairie legume
(2024-02) Pain, Rachel
Rapid climate change, alongside substantial habitat fragmentation, presents new challenges for biodiversity conservation in the tallgrass prairie. Therefore, capacity for adaptation in situ will be necessary for long-term population persistence. Populations with larger genetic variation likely have greater capacity for adaptation, but limited population sizes and restricted gene flow decrease this potential. Assisted gene flow (AGF) aims to increase adaptive capacity by introducing genetic material from populations that have undergone selection in warmer or drier environments. However, the addition of genetic diversity from geographically and genetically distant populations may disrupt local adaptation and ultimately decrease population performance. Here, I study how hybridization between populations over a geo-climatic gradient impacts their evolutionary capacity in response to warming temperatures. I used Chamaecrista fasciculata, a buzz-pollinated prairie annual to investigate the immediate and longer-term consequences of assisted gene flow in the Minnesota tallgrass prairie. In Chapter 1, I found that local gene flow increased population fitness compared to long distance or no gene flow scenarios in both ambient and warmed conditions and that the offspring of long-distance hybridization were limited by their capacity to germinate in Minnesota. In Chapter 2, I assessed how hybridization along this geo-climatic gradient impacted the capacity for ongoing adaptation and its dependence on environmental conditions. I found that the VA(W) of hybrids was more clearly expressed in warming conditions compared to the focal populations, thus providing evidence of capacity for adaptation in hybrid populations exposed to warmer temperatures. In Chapter 3, I evaluated the impact of hybridization on floral trait plasticity. Although I detected plasticity in almost all floral traits and found no significant difference in trait values between populations, the effect of those traits on population fitness differed significantly between populations. Together these chapters provide an empirical examination of the theoretical expectations of gene flow on a complex landscape and provide substantial evidence of the importance of maintaining genetically variable populations in a changing climate.
Experimental evolution of increased size and complexity in Anabaena variabilis
(2014-05) Jacobsen, Kristin Alexa
The evolution of multicellularity has occurred over 25 times in the history of life. Previously, we have shown the evolution of multicellular traits can readily be observed in laboratory populations across model unicellular organisms like yeast, chlamydomonas, and E. coli. Cyanobacteria are the oldest multicellular organisms, dating back 3.5 billion years. Many species appear morphologically unchanged, suggesting they have remained primitively multicellular. Are they incapable of evolving increased complexity? Model prokaryote Anabaena is a filamentous cyanobacteria, predating fossil records, existing as single strands or loose mats with three distinct cells types. Rapid settling was used to select for increased size advantage. Response to selection resulted in dramatic size increase; microscopic strands became inseparable macroscopic aggregates. Anabaena also became more complex; growth rate increased, two distinguishable morphologies developed, and growth and reproduction patterns changed. This shows that Anabaena, although primitively multicellular for billions of years, rapidly evolves increased size and complexity.
Heritability and genetic correlations in the dental dimensions of Saguinus fuscicollis and Macaca mulatta
(2018-06) Hardin, Anna M.
The genetic inheritance of dental traits in primates is of interest to biological anthropologists due to the high-quality preservation of dental remains in the primate fossil record and, as a result, the frequent use of dental morphology in the study of primate evolution. Adaptive hypotheses for morphological evolution in the primate dentition often discuss individual teeth as independent characters, yet the dentition may be best described as an organ composed of serially homologous parts. Previous studies have shown that dental dimensions are both highly heritable and frequently genetically correlated with other dental features in human and baboon populations, yet it remains to be seen whether tooth size heritabilities and patterns of genetic correlation differ in primate populations with different living conditions or evolutionary histories. This dissertation uses quantitative genetic parameters estimated in the dental dimensions of brown-mantled tamarins (Saguinus fuscicollis) and rhesus macaques (Macaca mulatta) to address these blank spaces in our understanding of the genetic inheritance and integration of primate tooth size. The findings of this research further our knowledge of the genetic inheritance of tooth size in primates and generate new hypotheses about the impact of genetic integration on the evolution of the canine-premolar honing complex and the dentition more broadly.
Light-mediated Sexual Dimorphism in Opsin Expression During Spawning in Nematostella vectensis
(2024-04) Wagner, Starla J.; McCulloch, Kyle J.
Across animals, opsins are the primary protein responsible for light detection. Currently, there is a large gap in knowledge in the evolutionary history of opsin function and how it correlates with other biological responses like spawning. Cnidarians (jellyfish and anemones) are prime candidates for closing this gap. They are a sister taxon to bilaterally symmetric animals like flies and humans, and so studying their opsin function and expression in non-visual contexts allows for further understanding of how light sensing may have evolved to form modern visual systems. In this experiment, qPCR analysis on the Cnidarian, Nematostella vectensis (the starlet sea anemone), was used to determine the effect of certain wavelengths of light that an animal was exposed to during spawning had on opsin expression levels. The impact of sex and tissue type on these expression levels was an additional area of interest. The data showed that certain wavelengths like blue light were correlated with larger amounts of opsin expression in female mesenteries and tentacles/skin tissue than in male tissue types. This indicates that opsin expression is sexually dimorphic which implies there is a relationship between opsin expression and spawning, something that was previously unknown. Future experiments using RNA-seq will allow for a deeper understanding of this relationship and the proteins involved.
The morphology and evolution of tooth replacment in the combtooth blennies (Ovalentaria: Blenniidae)
(2020-07) Williams, Keiffer
This research investigates the morphology and evolution of tooth replacement in the combtooth blennies. Blennies exhibit complex dentition that is not easily categorized by previously established metrics of teleost tooth replacement (extraosseous and intraosseous replacement). Most blennies are heterodont, possessing a single row of comb-shaped feeding teeth on the anterior portion of their jaws, and enlarged canines on the posterior portion of their lower jaws used for agonistic interactions. However, this bizarre dentition has been intentionally overlooked in classic surveys of teleost dentition due to its complexity. In Chapter 1, I investigate how feeding teeth are replaced in salariin blennies by establishing a descriptive model of tooth replacement for the Pacific Leaping Blenny, Alticus arnoldorum. This fish exhibits tooth replacement and tooth attachment that defy the discrete categorizations used for most other teleost dentitions. Using my descriptive model, I then propose hypotheses of how feeding teeth function in this fish. In chapter 2, I investigate how modes of tooth replacement have evolved in blennies. I find that canines in blennies are consistently replaced intraosseously, while feeding teeth across the family vary from intraosseous to a derived form of extraosseous replacement. These results further support the concept of teleost tooth replacement as a continuum rather than discretely classified modes. My results also suggest teleost tooth replacement needs to be carefully examined within a phylogenetic context to better understand how trophic morphological novelties evolve, as modes of tooth replacement likely play a key role in ecological and functional morphological shifts in teleosts.
Reconstructing the bay-side geomorphic evolution of a freshwater baymouth bar in response to lake level change using three dimensional (3D) ground-penetrating radar (GPR) data
(2019-11) Kremmin, Todd
Situated at the southwestern tip of Lake Superior, Minnesota and Wisconsin Points' form a 16-kilometer baymouth bar between Duluth, Minnesota and Superior, Wisconsin, providing the breakwater for the largest and farthest inland freshwater seaport in North America. Comprised of sandy sediment, this baymouth bar's formation is attributed largely to littoral drift from the Wisconsin South Shore and minor sediments from the outflows of the St. Louis and Nemadji River's. Due to continuing differential isostatic rebound of the basin, local lake level at Duluth is presently rising at approximately 25 centimeters/century. The objective of this thesis was to understand the geomorphic evolution of the bay-side of the baymouth bar in response to lake level change in relation to the system overall. Using an approach akin to energy industry seismic studies, the geomorphic expression of the bay-side baymouth bar’s response to lake level change was investigated with 39.62 kilometers of Three-Dimensional (3D) Ground-Penetrating Radar (GPR) data. 8 vibracores’, 11.24 meters’ in total, were advanced within the 3D GPR data to supplement subsurface understanding both spatially and temporally. Radiocarbon material taken from the vibracores were analyzed, dated, and used to establish a chronology for the evolution of the study area (~520.50 Cal yrs. BP to 181.25 Cal yrs. BP). Whole core logger data (including p-wave amplitude and velocity, gamma ray density, acoustic impedance, and fractional porosity) along with Loss on Ignition (LOI) samples taken from each core were used in conjunction with the GPR data to supplement the subsurface stratigraphic and facies identification. In total, 5 facies units were interpreted on the bay side of the baymouth bar, exhibiting a thick clay layer, shoreface ridge and shallow offshore sediments, overwash deposition, fluvial-flood like deposition, and man-made dredge deposits. Historical information and photographs dating back to the 1930’s provide evidence supporting interpretations of dredge material versus natural material. Although this baymouth bar is a young, non-marine system, reconstructing its geomorphic evolution in response to lake level change has become a useful analogue for similar, larger systems involved with base level change. In addition, stratigraphic findings of how such a system’s architecture is configured yield insightful clues towards vintage conventional exploration reservoirs. Finally, these data support a stronger understanding of how such a system geomorphically evolved in the context of the Lake Superior region post glaciation and aid in reshaping knowledge of how other geomorphic features and processes have developed throughout the region, perhaps providing tangible framework for future engineering and environmental management undertakings.
Systematics, Biogeography, and Phylogeography of Thylamys Mouse Opossums, a Recent Radiation of Neotropical Marsupials
(2013-08) Giarla, Thomas Christopher
This project broadly explores the systematics, biogeography, and phylogeography of Thylamys mouse opossums, a genus of Neotropical marsupials from central and southern South America. Chapter 1 is part of a collaborative work with Robert Voss and Sharon Jansa (Chapter 1). In it, we resolve longstanding issues surrounding Thylamys taxonomy and nomenclature using mitochondrial DNA sequences and morphology, and provide the first phylogenetic hypothesis for all recognized species in this genus. We recognize nine species but also uncover numerous morphologically cryptic mitochondrial haplogroups within four species. In Chapter 2, I assess the evolutionary independence of a subset of these morphologically cryptic lineages within the montane species Thylamys pallidior, T. sponsorius, and T. venustus. I find evidence to support the existence of two lineages within each of the three species, and also conduct tests to determine the number of nuclear loci needed to confidently test species limits. In Chapter 3, I examine the biogeographic history of Thylamys and its monotypic sister-genus Lestodelphys, considering the impact of habitat type and physical barriers on range evolution and cladogenesis. In Chapter 4, I test predictions regarding the impact of late Quaternary glacial cycles on the evolutionary history of six montane cryptic lineages. I estimate divergence times and demographic shifts for each lineage, and find limited support for the core predictions. Two supplementary files are provided online as part of this dissertation: a file containing 15 phylogenetic trees for each of the loci considered in Chapter 2 (Online Supplementary File 1) and a file containing GenBank accession numbers and tissue voucher numbers for the sequences included in the supermatrix in Chapter 3 (Online Supplementary File 2).
Thermoregulation and marathon performance: relationships of predictability of marathon performance, ambient weather conditions, BSA:MT, BSA:ML, percent body fat, and aerobic fitness
(2012-11) Roach, Laura Elizabeth
The purpose of this study was to observe individual variance in the ability to predict marathon performance from a two-mile time trial performance and determine whether the variance in predictability is influenced by thermoregulatory advantages of body size. Over three distinct marathon conditions, 126 (n =17 in 2010, n =42 in 2011, n =67 in 2012) aerobically-trained college physical activity students participated in pre- and post-anthropometric testing, a two-mile time trial on an indoor track, and concluded with the Eau Claire marathon. Between 72 and 98% of the variance in marathon performance could be explained by two-mile time trial performance. Variation of predicted performance from actual marathon performance was related to body surface area to mass ratio, body surface area to lean mass ratio, and percent body fat but depended on the race temperature, sex, and aerobic fitness. Notably, high body surface area to mass ratio was advantageous for sub-15 minute two-milers racing at an effective temperature of 12 degrees Celcius even though conditions were compensable. (r = 0.399, p< 0.033). The evidence shows that even in cold and mild conditions body surface area to mass ratio can affect marathon performance.

University Digital Conservancy

Browse by Subject

Browsing by Subject "Evolution"