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Evolution Of Sex Chromosomes In Geckos (Reptilia: Gekkota), Shannon Elizabeth Keating

Dissertations (1934 -)

Sex chromosomes control sex determination in many plants and animals, playing a vital role in a species’ evolution. Current models of sex chromosome evolution have been formulated by studying clades with stable, morphologically distinct (heteromorphic) sex chromosomes, such as mammals and birds. However, many taxa have morphologically indistinguishable (homomorphic) sex chromosomes, including many fish, amphibians, and reptiles. The knowledge gained from these understudied systems may provide new insights into the overarching paradigms of sex chromosome evolution. Thus, the historical focus on stable, heteromorphic sex chromosomes and failure to consider homomorphic sex chromosomes or systems with frequent turnovers may mean the …

Implications Of The Actin Cytoskeleton On The Multi-Step Process Of [ Psi+] Prion Formation, Jane E. Dorweiler, Douglas R. Lyke, Nathan P. Lemoine, Samantha Guereca, Hannah E. Buchholz, Emily R. Legan, Claire M. Radtke, Anita L. Manogaran

Biological Sciences Faculty Research and Publications

Yeast prions are self-perpetuating misfolded proteins that are infectious. In yeast, [PSI⁺] is the prion form of the Sup35 protein. While the study of [PSI⁺] has revealed important cellular mechanisms that contribute to prion propagation, the underlying cellular factors that influence prion formation are not well understood. Prion formation has been described as a multi-step process involving both the initial nucleation and growth of aggregates, followed by the subsequent transmission of prion particles to daughter cells. Prior evidence suggests that actin plays a role in this multi-step process, but actin’s precise role is unclear. Here, we …

Plant Growth-Promoting Activity Of Bacteria Isolated From Asian Rice (Oryza Sativa L.) Depends On Rice Genotype, Nasim Maghboli Balasjin, James Maki, Michael Schläppi, Christopher Marshall

Biological Sciences Faculty Research and Publications

Asian rice is one of the most important crops because it is a staple food for almost half of the world’s population. To have production of rice keep pace with a growing world population, it is anticipated that the use of fertilizers will also need to increase, which may cause environmental damage through runoff impacts. An alternative strategy to increase crop yield is the use of plant growth-promoting bacteria. Thousands of microbial species can exist in association with plant roots and shoots, and some are critical to the plant’s survival. We isolated 140 bacteria from two distantly related rice accessions …

Immunosuppression Broadens Evolutionary Pathways To Treatment Failure During Acinetobacter Baumannii Pneumonia, Wenwen Huo, Lindsay M. Busch, Juan Hernandez-Bird, Efrat Hamami, Christopher Marshall, Edward Geisinger, Vaughn S. Cooper, Tim Van Opijnen, Jason W. Rosch, Ralph R. Isberg

Biological Sciences Faculty Research and Publications

Acinetobacter baumannii is increasingly refractory to antibiotic treatment in healthcare settings. As is true of most human pathogens, the genetic path to antimicrobial resistance (AMR) and the role that the immune system plays in modulating AMR during disease are poorly understood. Here we reproduced several routes to fluoroquinolone resistance, performing evolution experiments using sequential lung infections in mice that are replete or depleted of neutrophils, providing two key insights into the evolution of drug resistance. First, neutropenic hosts acted as reservoirs for the accumulation of drug resistance during drug treatment. Selection for variants with altered drug sensitivity profiles arose readily …

Lianas Decelerate Tropical Forest Thinning During Succession, Jose A. Medina-Vega, Geertje M. F. Van Der Heijden, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

The well-established pattern of forest thinning during succession predicts an increase in mean tree biomass with decreasing tree density. The forest thinning pattern is commonly assumed to be driven solely by tree-tree competition. The presence of non-tree competitors could alter thinning trajectories, thus altering the rate of forest succession and carbon uptake. We used a large-scale liana removal experiment over 7 years in a 60- to 70-year-old Panamanian forest to test the hypothesis that lianas reduce the rate of forest thinning during succession. We found that lianas slowed forest thinning by reducing tree growth, not by altering tree recruitment or …

Immunosuppression Broadens Evolutionary Pathways To Drug Resistance And Treatment Failure During Acinetobacter Baumannii Pneumonia In Mice, Wenwen Ho, Lindsay M. Busch, Juan Hernandez-Bird, Efrat Hamami, Christopher Marshall, Edward Geisinger, Vaughn S. Cooper, Tim Van Opijnen, Jason W. Rosch, Ralph R. Isberg

Biological Sciences Faculty Research and Publications

Acinetobacter baumannii is increasingly refractory to antibiotic treatment in healthcare settings. As is true of most human pathogens, the genetic path to antimicrobial resistance (AMR) and the role that the immune system plays in modulating AMR during disease are poorly understood. Here we reproduced several routes to fluoroquinolone resistance, performing evolution experiments using sequential lung infections in mice that are replete with or depleted of neutrophils, providing two key insights into the evolution of drug resistance. First, neutropenic hosts acted as reservoirs for the accumulation of drug resistance during drug treatment. Selection for variants with altered drug sensitivity profiles arose …

B-Vitamins Influence The Consumption Of Macronutrients In Honey Bees, Walaa Ahmed Elsayeh, Chelsea N. Cook, Geraldine A. Wright

Biological Sciences Faculty Research and Publications

Insects require dietary sources of B-vitamins, but relatively little is known about whether they regulate B-vitamin intake in the same way they regulate other nutrients. Honey bees meet their B-vitamin requirements mainly from the pollen they collect. Employing the geometric framework for nutrition, we found that honey bees actively regulate their vitamin intake following Bertrand’s rule. We fed bees with a diet of essential amino acids (EAAs) and carbohydrate (C) to identify how the addition of B-vitamins affected the regulation of these macronutrients. In our experiments, honey bees preferred vitamins in concentrations comparable to those found in honey bee food …

Evolved Resistance To A Novel Cationic Peptide Antibiotic Requires High Mutation Supply, Alfonso Santos-Lopez, Melissa J. Fritz, Jeffrey B. Lombardo, Ansen H.P. Burr, Victoria A. Heinrich, Christopher Marshall, Vaughn S. Cooper

Biological Sciences Faculty Research and Publications

Background and Objectives

A key strategy for resolving the antibiotic resistance crisis is the development of new drugs with antimicrobial properties. The engineered cationic antimicrobial peptide WLBU2 (also known as PLG0206) is a promising broad-spectrum antimicrobial compound that has completed Phase I clinical studies. It has activity against Gram-negative and Gram-positive bacteria including infections associated with biofilm. No definitive mechanisms of resistance to WLBU2 have been identified.

Methodology

Here, we used experimental evolution under different levels of mutation supply and whole genome sequencing (WGS) to detect the genetic pathways and probable mechanisms of resistance to this peptide. We propagated populations …

Tree Species Diversity Increases With Conspecific Negative Density Dependence Across An Elevation Gradient, Joseph A. Lamanna, F. Andrew Jones, Davod M. Bell, Robert J. Pabst, David C. Shaw

Biological Sciences Faculty Research and Publications

Elevational and latitudinal gradients in species diversity may be mediated by biotic interactions that cause density-dependent effects of conspecifics on survival or growth to differ from effects of heterospecifics (i.e. conspecific density dependence), but limited evidence exists to support this. We tested the hypothesis that conspecific density dependence varies with elevation using over 40 years of data on tree survival and growth from 23 old-growth temperate forest stands across a 1,000-m elevation gradient. We found that conspecific-density-dependent effects on survival of small-to-intermediate-sized focal trees were negative in lower elevation, higher diversity forest stands typically characterised by warmer temperatures and greater …

Chromosome-Level Genome Assembly Reveals Dynamic Sex Chromosomes In Neotropical Leaf-Litter Geckos (Sphaerodactylidae: Sphaerodactylus), Brendan J. Pinto, Shannon E. Keating, Stuart V. Nielsen, Daniel P. Scantlebury, Juan D. Daza, Tony Gamble

Biological Sciences Faculty Research and Publications

Sex determination is a critical element of successful vertebrate development, suggesting that sex chromosome systems might be evolutionarily stable across lineages. For example, mammals and birds have maintained conserved sex chromosome systems over long evolutionary time periods. Other vertebrates, in contrast, have undergone frequent sex chromosome transitions, which is even more amazing considering we still know comparatively little across large swaths of their respective phylogenies. One reptile group in particular, the gecko lizards (infraorder Gekkota), shows an exceptional lability with regard to sex chromosome transitions and may possess the majority of transitions within squamates (lizards and snakes). However, detailed genomic …

Pituitary Adenylate Cylase-Activating Polypeptide Receptor: Multiple Signaling Pathways Involved In Energy Homeostasis, Brian Maunze

Dissertations (1934 -)

Pituitary adenylate cyclase activating polypeptide (PACAP) exerts pleiotropic effects on ventromedial nuclei (VMN) of the hypothalamus and its control of feeding and energy expenditure through the Type I PAC1 receptor (PAC1R). However, the endogenous role of PAC1R’s in the VMN and the downstream signaling responsible for PACAP’s effects are unknown.To determine the endogenous role of PAC1Rs and signaling that may explain PACAP’s pleiotropic effects, we knocked down VMN PAC1Rs and pharmacologically inhibited PKA, PKC and PAC1R trafficking. Knocking down PAC1Rs increased meal sizes, reduced total number of meals, and induced body weight gain. Inhibition of either PKA or PKC alone …

The Evolutionary History Of An Accidental Model Organism, The Leopard Gecko Eublepharis Macularius (Squamata: Eublepharidae), Ishan Agarwal, Aaron M. Bauer, Tony Gamble, Varad B. Giri, Daniel Jablonski, Akshay Khandekar, Pratyush P. Mohapatra, Rafaqat Masroor, Anurag Mishra, Uma Ramakrishnan

Biological Sciences Faculty Research and Publications

The leopard gecko, Eublepharis macularius, is a widely used model organism in laboratory and experimental studies. The high phenotypic diversity in the pet trade, the fact that the provenance of different breeding lines is unknown, and that distinct Eublepharis species are known to hybridize, implies that the continued use of E. macularius as a model requires clarity on the origin of the lineages in the pet trade. We combine multi-locus sequence data and the first range-wide sampling of the genus Eublepharis to reconstruct the evolutionary history of the Eublepharidae and Eublepharis, with an updated time-tree for the Eublepharidae. …

Convergent Developmental Patterns Underlie The Repeated Evolution Of Adhesive Toe Pads Among Lizards, Aaron H. Griffing, Tony Gamble, Martin J. Cohn, Thomas J. Sanger

Biological Sciences Faculty Research and Publications

How developmental modifications produce key innovations, which subsequently allow for rapid diversification of a clade into new adaptive zones, has received much attention. However, few studies have used a robust comparative framework to investigate the influence of evolutionary and developmental constraints on the origin of key innovations, such as the adhesive toe pad of lizards. Adhesive toe pads evolved independently at least 16 times in lizards, allowing us to examine whether the patterns observed are general evolutionary phenomena or unique, lineage-specific events. We performed a high-resolution comparison of plantar scale development in 14 lizard species in Anolis and geckos, encompassing …

Atypical Tuning And Amplification Mechanisms In Gecko Auditory Hair Cells, Maryline Beurg, Tony Gamble, Aaron H. Griffing, Robert Fettiplace

Biological Sciences Faculty Research and Publications

The auditory papilla of geckos contains two zones of sensory hair cells, one covered by a continuous tectorial membrane affixed to the hair bundles and the other by discrete tectorial sallets each surmounting a transverse row of bundles. Gecko papillae are thought to encode sound frequencies up to 5 kHz, but little is known about the hair cell electrical properties or their role in frequency tuning. We recorded from hair cells in the isolated auditory papilla of the crested gecko, Correlophus ciliatus, and found that in both the nonsalletal region and part of the salletal region, the cells displayed …

Making (Remote) Sense Of Lianas, Geertje M. F. Van Der Heijden, Ashley D. C. Proctor, Kim Calders, Chris J. Chandler, Richard Field, Giles M. Foody, Sruthi M. Krishna Moorthy, Stefan A. Schnitzer, Catherine E. Waite, Doreed S. Boyd

Biological Sciences Faculty Research and Publications

1. Lianas (woody vines) are abundant and diverse, particularly in tropical ecosystems. Lianas use trees for structural support to reach the forest canopy, often putting leaves above their host tree. Thus they are major parts of many forest canopies. Yet, relatively little is known about distributions of lianas in tropical forest canopies, because studying those canopies is challenging. This knowledge gap is urgent to address because lianas compete strongly with trees, reduce forest carbon uptake and are thought to be increasing, at least in the Neotropics.
2. Lianas can be difficult to study using traditional field methods. Their pliable stems often twist …

Establishment Of Common House Geckos, Hemidactylus Frenatus Duméril & Bibron, On Saint Lucia, Aaron H. Griffing, David H. Griffing, Stephen Lesmond, Tony Gamble

Biological Sciences Faculty Research and Publications

No abstract provided.

Similarities In Virulence And Extended Spectrum Beta-Lactamase Gene Profiles Among Cefotaxime-Resistant Escherichia Coli Wastewater And Clinical Isolates, Elizabeth Liedhegner, Brandon Bojar, Rachelle E. Beattie, Caitlin Cahak, Krassimira R. Hristova, Troy Skwor

Biological Sciences Faculty Research and Publications

The World Health Organization has identified antibiotic resistance as one of the largest threats to human health and food security. In this study, we compared antibiotic resistance patterns between ESBL-producing Escherichia coli from human clinical diseases and cefotaxime-resistant environmental strains, as well as their potential to be pathogenic. Antibiotic susceptibility was tested amongst clinical isolates (n = 11), hospital wastewater (n = 22), and urban wastewater (n = 36, both influent and treated effluents). Multi-drug resistance predominated (>70%) among hospitalwastewater and urban wastewater influent isolates. Interestingly, isolates from clinical and urban treated effluents showed similar multi-drug …

Lianas Significantly Reduce Aboveground And Belowground Carbon Storage: A Virtual Removal Experiment, Sergio Estrada-Villegas, Sara Sofia Pedraza Navaez, Adriana Sanchez, Stefan A. Schnitzer

Biological Sciences Faculty Research and Publications

Lianas are a quintessential tropical plant growth-form; they are speciose and abundant in tropical forests worldwide. Lianas compete intensely with trees, reducing nearly all aspects of tree performance. However, the negative effects of lianas on trees have never been combined and quantified for multiple tropical forests. Here, we present the first comprehensive standardized quantification of the effect of lianas on trees across tropical forests worldwide. We used data from 50 liana removal experiments and quantified the effect size of lianas on tree growth, biomass accretion, reproduction, mortality, leaf water potential, sap flow velocity, and leaf area index (LAI) across different …

Sex-Specific Aging In Animals: Perspective And Future Directions, Anne M. Bronikowski, Richard P. Meisel, Peggy R. Biga, James R. Walters, Judith E. Mank, Erica Larschan, Gerald S. Wilkinson, Nicole Valenzuela, Ashley Mae Conard, João Pedro De Magalhães, Jingyue (Ellie) Duan, Amy E. Elias, Tony Gamble, Rita M. Graze, Kristin E. Gribble, Jill A. Kreiling, Nicole C. Riddle

Biological Sciences Faculty Research and Publications

Sex differences in aging occur in many animal species, and they include sex differences in lifespan, in the onset and progression of age-associated decline, and in physiological and molecular markers of aging. Sex differences in aging vary greatly across the animal kingdom. For example, there are species with longer-lived females, species where males live longer, and species lacking sex differences in lifespan. The underlying causes of sex differences in aging remain mostly unknown. Currently, we do not understand the molecular drivers of sex differences in aging, or whether they are related to the accepted hallmarks or pillars of aging or …

Response Of Antarctic Soil Fauna To Climate-Driven Changes Since The Last Glacial Maximum, Andre L.C. Franco, Byron J. Adams, Melisa A. Diaz, Nathan P. Lemoine, Nicholas B. Dragone, Noah Fierer, W. Berry Lyons, Ian Hogg, Diana H. Wall

Biological Sciences Faculty Research and Publications

Understanding how terrestrial biotic communities have responded to glacial recession since the Last Glacial Maximum (LGM) can inform present and future responses of biota to climate change. In Antarctica, the Transantarctic Mountains (TAM) have experienced massive environmental changes associated with glacial retreat since the LGM, yet we have few clues as to how its soil invertebrate-dominated animal communities have responded. Here, we surveyed soil invertebrate fauna from above and below proposed LGM elevations along transects located at 12 features across the Shackleton Glacier region. Our transects captured gradients of surface ages possibly up to 4.5 million years and the soils …

The Mitospecific Domain Of Mrp7 (Bl27) Supports Mitochondrial Translation During Fermentation And Is Required For Effective Adaptation To Respiration, Jessica M. Anderson, Jodie M. Box, Rosemary A. Stuart

Biological Sciences Faculty Research and Publications

We demonstrate here that mitoribosomal protein synthesis, responsible for the synthesis of oxidative phosphorylation (OXPHOS) subunits encoded by the mitochondrial genome, occurs at high levels during glycolysis fermentation and in a manner uncoupled from OXPHOS complex assembly regulation. Furthermore, we provide evidence that the mitospecific domain of Mrp7 (bL27), a mitoribosomal component, is required to maintain mitochondrial protein synthesis during fermentation but is not required under respiration growth conditions. Maintaining mitotranslation under high-glucose-fermentation conditions also involves Mam33 (p32/gC1qR homologue), a binding partner of Mrp7’s mitospecific domain, and together they confer a competitive advantage for a cell’s ability to adapt to …

Local Canopy Disturbance As An Explanation For Long-Term Increases In Liana Abundance, Stefan A. Schnitzer, David M. Defilippis, Marco Visser, Sergio Estrada-Villegas, Rigoberto Rivera-Camaña, Boris Bernal, Salomé Peréz, Abelino Valdéz, Seberino Valdéz, Antonio Aguilar, James W. Dalling, Eben N. Broadbent, Angelica M. Almeyda Zambrano, Stephen P. Hubbell, Maria Garcia-Leon

Biological Sciences Faculty Research and Publications

Canopy disturbance explains liana abundance and distribution within tropical forests and thus may also explain the widespread pattern of increasing liana abundance; however, this hypothesis remains untested. We used a 10-year study (2007–2017) of 117,100 rooted lianas in an old-growth Panamanian forest to test whether local canopy disturbance explains increasing liana abundance. We found that liana density increased 29.2% and basal area 12.5%. The vast majority of these increases were associated with clonal stem proliferation following canopy disturbance, particularly in liana-dense, low-canopy gaps, which had far greater liana increases than did undisturbed forest. Lianas may be ecological niche constructors, arresting …

Comparative Riverscape Genomics Of The Rainbow Darter (Etheostoma Caeruleum) In Glaciated And Unglaciated Environments, Jon M. Luiken, Tony Gamble, Peter B. Berendzen

Biological Sciences Faculty Research and Publications

Periodic glaciation during the Quaternary period shaped the contemporary riverscape and distribution of freshwater fishes in the Mississippi River drainage of central North America. The rainbow darter (Etheostoma caeruleum) is a member of this ichthyofauna and has a disjunct distribution in glaciated and unglaciated environments west of the Mississippi River. Based on glacial history of the region, there are different expectations on the observed spatial genetic structure of populations in these environments. The aim of this study was to utilize genome-wide SNP data to compare the population genomic structure of the rainbow darter in river networks with disparate …

Phenology Dictates The Impact Of Climate Change On Geographic Distributions Of Six Co-Occurring North American Grasshoppers, Nathan P. Lemoine

Biological Sciences Faculty Research and Publications

Throughout the last century, climate change has altered the geographic distributions of many species. Insects, in particular, vary in their ability to track changing climates, and it is likely that phenology is an important determinant of how well insects can either expand or shift their geographic distributions in response to climate change. Grasshoppers are an ideal group to test the hypothesis that phenology correlates with range expansion, given that co-occurring confamilial, and even congeneric, species can differ in phenology. Here, I tested the hypothesis that early- and late-season species should possess different range expansion potentials, as estimated by habitat suitability …

The Philosophy Of Outliers: Reintegrating Rare Events Into Biological Science, Chelsea N. Cook, Angela R. Freeman, James C. Liao, Lisa A. Mangiamele

Biological Sciences Faculty Research and Publications

Individual variation in morphology, physiology, and behavior has been a topic of great interest in the biological sciences. While scientists realize the importance of understanding diversity in individual phenotypes, historically the “minority” results (I.e., outlier observations or rare events) of any given experiment have been dismissed from further analysis. We need to reframe how we view “outliers” to improve our understanding of biology. These rare events are often treated as problematic or spurious, when they can be real rare events or individuals driving evolution in a population. It is our perspective that to understand what outliers can tell us in …

Herbivores Alleviate The Negative Effects Of Extreme Drought On Plant Community By Enhancing Dominant Species, Chong Xu, Yuguang Ke, Honghui Wu, Melinda D. Smith, Nathan P. Lemoine, Weiguo Zhang, Qiang Yu

Biological Sciences Faculty Research and Publications

Aims

Both extreme drought and insect herbivores can suppress plant growth in grassland communities. However, most studies have examined extreme drought and insects in isolation, and there is reason to believe that insects might alter the ability of grasslands to withstand drought. Unfortunately, few studies have tested the interactive effects of extreme drought and insect herbivores in grassland communities.

Methods

Here, we tested the drought–herbivore interactions using a manipulative experiment that factorially crossed extreme drought with the exclusion of insect herbivores in a temperate semiarid grassland in Inner Mongolia.

Important Findings

Our results demonstrated that both extreme drought and insect …

Low Temperature Antioxidant Activity Qtl Associate With Genomic Regions Involved In Physiological Cold Stress Tolerance Responses In Rice (Oryza Sativa L.), Huy Phan, Michael Schläppi

Biological Sciences Faculty Research and Publications

Boosting cold stress tolerance in crop plants can minimize stress-mediated yield losses. Asian rice (Oryza sativa L.), one of the most consumed cereal crops, originated from subtropical regions and is generally sensitive to low temperature environments. Within the two subspecies of rice, JAPONICA, and INDICA, the cold tolerance potential of its accessions is highly variable and depends on their genetic background. Yet, cold stress tolerance response mechanisms are complex and not well understood. This study utilized 370 accessions from the Rice Diversity Panel 1 (RDP1) to investigate and correlate four cold stress tolerance response phenotypes: membrane damage, …

Temperature Stressed Caenorhabditis Elegans Males Fail To Mate Successfully And Successful Males Produce Very Few Viable Cross Progeny, Nicholas B. Sepulveda, Lisa N. Petrella

Biological Sciences Faculty Research and Publications

Exposure to moderate temperature stress can have profoundly negative effects on an organism’s reproductive capacity at temperatures where there are minimal or indiscernible effects on the organism as a whole. These negative effects are often more pronounced in males of the species that produce sperm. Previously we showed that few males of Caenorhabditis elegans wild type strains are able to successfully produce any cross progeny after experiencing temperature stress. However, these experiments did not assess the number of progeny from temperature stressed males. To understand if temperature stress can reduce the number of progeny a male sires, we crossed temperature …

The Timing Of Intermittent Hypoxia Differentially Affects Macronutrient Intake And Energy Substrate Utilization In Mice, Sarah N. Framnes-Deboer, Aaron A. Jones, Michelle Y. Kang, Kat Propsom, Lauren R. Nelson, Deanna M. Arble

Biological Sciences Faculty Research and Publications

Sleep apnea is a common sleep disorder characterized by periodic breathing cessation and intermittent hypoxia (IH). Although previous studies have demonstrated that IH alone can influence metabolic outcomes such as body weight, it remains unclear how the timing of IH can specifically affect these outcomes. Here, we examine how pairing 10-h periods of IH to either the animals’ resting phase (e.g., IH during the day) or active phase (e.g., IH during the night) differentially affects body weight, macronutrient selection, energy expenditure, respiratory exchange rate, and glucose tolerance. We find that in contrast to mice exposed to IH during the night, …

Effects Of Low-Level Artificial Light At Night On Kentucky Bluegrass And An Introduced Herbivore, Morgan Crump, Cassandra Brown, Robert J. Griffin-Nolan, Lisa Angenoli, Nathan P. Lemoine, Brett M. Seymoure

Biological Sciences Faculty Research and Publications

Increasing evidence suggests that artificial light at night (ALAN) can negatively impact organisms. However, most studies examine the impacts of ALAN on a single species or under high levels of artificial light that are infrequent or unrealistic in urban environments. We currently have little information on how low levels of artificial light emanating from urban skyglow affect plants and their interactions with herbivores. We examined how short-term, low levels of ALAN affect grass and insects, including growth rate, photosynthesis, and stomatal conductance in grass, and foraging behavior and survival in crickets. We compared growth and leaf-level gas exchange of Kentucky …