Evolution Commons^™

Morphology Of Smallmouth Bass (Micropterus Dolomieu) In Arkansas, Robert Laroche

Biological Sciences Undergraduate Honors Theses

The Smallmouth Bass, Micropterus dolomieu, is one of the most important game fishes in Arkansas. Three distinct lineages are recognized from different river basins: the Northern, Neosho, and Ouachita Smallmouth Bass. Understanding the biodiversity within this species complex inhabiting different water bodies in Arkansas is important for effective management of the fisheries resource and to guide conservation efforts. But current data on distribution of distinct forms are insufficient to guide management. The primary goals of the study presented here was to quantify morphological characteristics to identify distinct lineages of Smallmouth Bass, and to determine their specific locations within Arkansas streams …

Structural Molecular And Developmental Evidence For Cell-Type Diversity In Cnidarian Mechanosensory Neurons, Julia Baranyk, Kristen Malir, Miguel A.P. Silva, Sakura Rieck, Gracie Scheve, Nagayasu Nakanishi

Biological Sciences Faculty Publications and Presentations

Deploying a conserved mechanosensory neuron known as the concentric hair cell, cnidarians have evolved diverse mechanoreceptors from hydroid filiform tentacles to jellyfish statocysts. However, it is unknown whether cnidarian mechanoreceptor evolution has relied solely on repurposing a single ancestral mechanosensory neuron type. Here we report evidence for cell-type diversity of mechanosensory neurons in sea-anemone cnidarian Nematostella vectensis. Uncovered in the ectoderm of feeding tentacles are conventional type I hair cells and previously unrecognized type II hair cells differing in the structure of apical sensory apparatus and synapses. Moreover, we identify TRP channel-encoding gene polycystin-1 as a type-II-hair-cell-specific essential mediator of …

Ontogenetic Biomechanics Of Tufted (Sapajus) And Untufted (Cebus) Capuchin Mandibles, Taylor A. Polvadore, Caitlin B. Yoakum, Parker M. Taylor, Megan A. Holmes, Myra F. Laird, Janine Chalk-Wilayto, Claudia Misue Kanno, Jose Americano De Oliveira, Claire E. Terhune

Anthropology Faculty Publications and Presentations

Objectives

Cortical bone geometry is commonly used to investigate biomechanical properties of primate mandibles. However, the ontogeny of these properties is less understood. Here we investigate changes in cortical bone cross-sectional properties throughout capuchin ontogeny and compare captive versus wild, semi-provisioned groups. Tufted capuchins (Sapajus spp.) are known to consume relatively hard/tough foods, while untufted capuchins (Cebus spp.) exploit less mechanically challenging foods. Previous research indicates dietary differences are present early in development and adult Sapajus mandibles can resist higher bending/shear/torsional loads.

Materials and methods

This study utilized microCT scans of 22 Cebus and 45 Sapajus from early …

Diverse Origins Of Near-Identical Antifreeze Proteins In Unrelated Fish Lineages Provide Insights Into Evolutionary Mechanisms Of New Gene Birth And Protein Sequence Convergence, Nathan Rives, Vinita Lamba, C.H. Christina Cheng, Xuan Zhuang

Biological Sciences Faculty Publications and Presentations

Determining the origins of novel genes and the mechanisms driving the emergence of new functions is challenging yet crucial for understanding evolutionary innovations. Recently evolved fish antifreeze proteins (AFPs) offer a unique opportunity to explore these processes, particularly the near-identical type I AFP (AFPI) found in four phylogenetically divergent fish taxa. This study tested the hypothesis of protein sequence convergence beyond functional convergence in three unrelated AFPI-bearing fish lineages. Through comprehensive comparative analyses of newly sequenced genomes of winter flounder and grubby sculpin, along with available high-quality genomes of cunner and 14 other related species, the study revealed that near-identical …

Robust Phylogenetic Regression, Richard Adams, Zoe Cain, Raquel Assis, Michael Degiorgio

Entomology and Plant Pathology Faculty Publications and Presentations

Modern comparative biology owes much to phylogenetic regression. At its conception, this technique sparked a revolution that armed biologists with phylogenetic comparative methods (PCMs) for disentangling evolutionary correlations from those arising from hierarchical phylogenetic relationships. Over the past few decades, the phylogenetic regression framework has become a paradigm of modern comparative biology that has been widely embraced as a remedy for shared ancestry. However, recent evidence has shown doubt over the efficacy of phylogenetic regression, and PCMs more generally, with the suggestion that many of these methods fail to provide an adequate defense against unreplicated evolution—the primary justification for using …

Unveiling The Ancestral Function Of A Neuroendocrine Regulator, Pou-I/Pit1: Insights From Gene Expression Analysis In The Sea Anemone Nematostella Vectensis, Miguel Agostinho Pina Da Silva

Graduate Theses and Dissertations

Cnidaria (i.e., sea anemones, jellyfish, corals) and Bilateria (i.e., vertebrates, sea stars, fruit flies), are sister groups that diverged around 600 million years ago. Despite the long evolutionary time, many cellular differentiation mechanisms, cell types, tissues and behaviors are conserved. Such as neurons, mechanosensory hair cells, feeding behaviors, peristaltic movements, and sleep. Recent advances in genomics, molecular biology and microscopy have fueled an increased interest in understanding cnidarian nervous and neuroendocrine systems. Understanding the developmental mechanisms and the mode of operation of Cnidarian nervous systems helps to reconstruct the ancestral nervous system of the last common ancestor of Cnidaria and …

The Scaling Method: Body Mass Reconstruction Of East African Hominins, Julianna Rose

Anthropology Undergraduate Honors Theses

This thesis details a series of novel methods developed to estimate body masses of hominin fossils using 3-D point cloud registration software. All analyses were conducted through 3-D modeling software that supported the remote study of five fossil femora from East Africa. The fossil computer models were repeatedly aligned with anatomically modern human femora to determine their scaling relationship with the objective of using the scaling factor of the human references to estimate the body mass of the fossils, on the basis of the femoral head breadth. Body mass estimates obtained through this technique were compared to estimates using more …

Hiding In Plain Sight: Accounting For Rate Heterogeneity In Trait Evolution Models, James Boyko

Graduate Theses and Dissertations

Within the last four decades, phylogenetic comparative methods have become the defacto method of analysis for comparative biologists. The availability of high-quality comparative datasets has been matched by an explosion of possible phylogenetic models. In large part, the efforts to increase the realism of phylogenetic comparative methods has been successful as evidenced by their widespread use. To this extensive literature, my contributions are modest. I have focused my dissertation work on two main themes. First, most phenotypic evolution is not independent of other phenotypes. Changes in a particular character may influence changes in another and modeling these characters in isolation …

Riverscape Community Genomics Of Ozark Fishes: A Comparative Framework To Infer Ecological And Evolutionary Determinants Of Genetic Diversity, Zachery D. Zbinden

Graduate Theses and Dissertations

Genetic variation is a crucial component of biodiversity and represents the variability and spatial structure of alleles within and among organisms. Evolution modulates this variability over time through mutation, selection, gene flow, and genetic drift. However, our capacity to test foundational theories of population genetics has always been at the mercy of molecular approaches available to quantify patterns of genetic diversity. Initially, techniques for empirical DNA studies were in their infancy and limited by technologies and the price per unit of genetic information. Because of these constraints, our pursuits have generally been limited to investigations of one or a few …

Rodent Dental Microwear Texture Analysis As A Proxy For Fine-Scale Paleoenvironment Reconstruction, Jenny H. E. Burgman

Graduate Theses and Dissertations

Dental microwear texture analysis (DMTA) of fossil fauna has become a valuable tool for dietary inference and paleoenvironment reconstruction. Most of this work has utilized larger taxa with larger home ranges. These studies may result in broader-scale habitat inferences that could mask the details of complex mosaic habitats. Rodent DMTA offers an opportunity to work at finer spatial scales because most species have smaller home ranges. Rodents are also keystone species within their ecosystems, abundant, ubiquitous, and found in many fossil deposits. These attributes make them excellent proxies for environmental reconstructions. However, the application of DMTA to rodents remains relatively …

Impact Of Genetic Variation And Timescale On Diatom Salinity Stress Response, Kala M. Downey

Graduate Theses and Dissertations

Natural environments are dynamic, and organisms must sense and respond to changing conditions. One common way organisms deal with stressful environments is through gene expression changes, allowing for stress acclimation and resistance which occurs over varying time spans in different species. The recent evolutionary history of populations could greatly influence their ability to respond successfully. An evolutionary history in disturbed or fluctuating conditions could promote increased resistance or a more rapid response to these environmental stressors. To understand the impact of genotypic variation and timescales on response and acclimation to salinity changes, we have been exploiting the abilities of euryhaline …

Dynamics Of Hybrid Zones At A Continental Scale, Bradley T. Martin

Graduate Theses and Dissertations

Hybridization has traditionally been viewed as a happenstance that negatively impacts populations, but is now recognized as an important evolutionary mechanism that can substantially impact the evolutionary trajectories of gene pools, influence adaptive capacity, and contravene or reinforce divergence. Physiographic processes are important drivers of dispersal, alternately funneling populations into isolation, promoting divergence, or facilitating secondary contact of diverged populations, increasing the potential for hybridization. In North America, glacial-interglacial cycles and geomorphological changes have provided a dynamic backdrop over the last two million years that promoted such oscillations of population contraction and expansion. These biogeographic processes have resulted in regional …

A Spatially Explicit Model Of Stabilizing Selection For Improving Phylogenetic Inference, Jeremy M. Beaulieu, Brian C. O'Meara, Michael A. Gilchrist

Biological Sciences Faculty Publications and Presentations

Ultraconserved elements (UCEs) are stretches of hundreds of nucleotides with highly conserved cores flanked by variable regions. Although the selective forces responsible for the preservation of UCEs are unknown, they are nonetheless believed to contain phylogenetically meaningful information from deep to shallow divergence events. Phylogenetic applications of UCEs assume the same degree of rate heterogeneity applies across the entire locus, including variable flanking regions. We present a Wright-Fisher model of selection on nucleotides (SeION) which includes the effects of mutation, drift, and spatially varying, stabilizing selection for an optimal nucleotide sequence. The SeION model assumes the strength of stabilizing selection …

A Macroevolutionary View On Extinction In Aves, Chiroptera, And Odonata, Peter Hasik

Graduate Theses and Dissertations

A central goal of conservation biology is to identify and understand the factors that lead to extinction. The Earth is currently undergoing a 6th mass extinction event, in large part because of human activity. In the last century, rates of extinction have increased anywhere from 8-100 times the background rate of 2 extinctions per 10,000 species every 100 years. However, there remains a debate over whether certain species are predisposed to a higher extinction risk. In particular, it is not known if the macroevolutionary history of a lineage is a major contributor to the probability of extinction, nor is it …

Evolutionary Inference From Admixed Genomes: Implications Of Hybridization For Biodiversity Dynamics And Conservation, Tyler Chafin

Graduate Theses and Dissertations

Hybridization as a macroevolutionary mechanism has been historically underappreciated among vertebrate biologists. Yet, the advent and subsequent proliferation of next-generation sequencing methods has increasingly shown hybridization to be a pervasive agent influencing evolution in many branches of the Tree of Life (to include ancestral hominids). Despite this, the dynamics of hybridization with regards to speciation and extinction remain poorly understood. To this end, I here examine the role of hybridization in the context of historical divergence and contemporary decline of several threatened and endangered North American taxa, with the goal to illuminate implications of hybridization for promoting—or impeding—population persistence in …

Characterization Of Microtubule Organizing Centers In The Genus Protostelium, Including Evolutionary Implications, Ethan Taylor Ozment

Graduate Theses and Dissertations

Microtubule organizing centers (MTOCs) are cellular regions of microtubule nucleation. The best known MTOCs are those associated with the centrosome, but several non-centrosomal MTOCs are known in eukaryotes, especially in land plants. MTOCs are poorly characterized across the breadth of amoebozoan diversity, but are well-known in certain amoebozoan lineages, including the genus of protosteloid slime molds Protostelium. The structure of the MTOC is known for two non-ciliated species, P. nocturnum and P. mycophaga, as well as P. aurantium, which can reversibly become ciliated under appropriate conditions. P. nocturnum and P. mycophaga have acentriolar centrosomal MTOCs while P. aurantium has a …

Phylogenomics And Geometric Morphometrics Define Species Flocks Of Snowtrout (Teleostei: Schizothorax) In The Central Himalayas, Binod Regmi

Graduate Theses and Dissertations

Schizothorax (Snowtrout) is a genus of medium-sized minnows (Cypriniformes) inhabiting glacier-fed streams, rivers, and lakes in the Himalayas. There are more than 30 species of Schizothorax across the region. The speciation and diversity of the Snowtrout in the vast hinterlands of the Himalayan Region has not been fully explored. Three species in Lake Rara, Western Nepal are considered a species flock, comprising endemic ecotypes that are morphologically differentiated and reproductively isolated.

My dissertation research examined the diversity of Schizothorax in the Central Himalayan region and evolutionary relationships among species distributed in the Tibet, Central and Southeast Asia. Chapter I describes …

Crispr Knockouts Reveal An Endogenous Role For Ancient Neuropeptides In Regulating Developmental Timing In A Sea Anemone, Nagayasu Nakanishi, Mark Q. Martindale

Biological Sciences Faculty Publications and Presentations

Neuropeptides are evolutionarily ancient peptide hormones of the nervous and neuroendocrine systems, and are thought to have regulated metamorphosis in early animal ancestors. In particular, the deeply conserved Wamide family of neuropeptides—shared across Bilateria (e.g. insects and worms) and its sister group Cnidaria (e.g. jellyfishes and corals)—has been implicated in mediating life-cycle transitions, yet their endogenous roles remain poorly understood. By using CRISPR-Cas9-mediated reverse genetics, we show that cnidarian Wamide—referred to as GLWamide—regulates the timing of life cycle transition in the sea anemone cnidarian Nematostella vectensis. We find that mutant planula larvae lacking GLWamides transform into morphologically normal polyps …

Evolutionary Conservation Of Midline Repulsion By Robo Family Receptors In Flies And Mice, Allison Loy

Biological Sciences Undergraduate Honors Theses

As the nervous system develops in animal embryos, neuronal axons are guided to their synaptic targets by extra cellular cues that signal through axon guidance receptors expressed on the surface of the axon. In animals with bilateral symmetry, one of the important decisions made by nearly every axon in the embryonic nervous system is whether to stay on its own side of the body, or to cross the midline and connect to cells on the opposite side. The Roundabout (Robo) family is an evolutionarily conserved group of axon guidance receptors that regulate midline crossing in a wide range of animal …

Phylogeny And Evolutionary Genomics Of Non-Photosynthetic Diatoms, Anastasiia Onyshchenko

Graduate Theses and Dissertations

Diatoms are prolific photosynthesizers responsible for some 20% of global primary production. In real terms, the oxygen in one of every five breaths traces back to photosynthesis by marine diatoms. Among the tens of thousands of diatom species, a small handful of colorless diatom species in the genus Nitzschia have lost photosynthesis altogether and rely exclusively on extracellular organic carbon for growth. I used DNA sequence data to reconstruct the phylogeny of this group, and found that nonphotosynthetic diatoms are monophyletic, indicating that photosynthesis was lost just one time over the course of some 200 million years of diatom evolution. …

Phylogeography And Vicariant Separation Of Two River Darters, Percina Uranidea And Percina Vigil, From Rivers That Drain The North American Interior Highlands, T. Yamashita, J. M. Rigsby, J. Stoeckel

Journal of the Arkansas Academy of Science

The phylogeography and separation of two river darters, Percina uranidea and P. vigil were investigated through sequencing of the mitochondrial Cytochrome B and Cytochrome Oxidase genes. These molecular markers revealed the darters exhibit moderate genetic divergence between two large river drainage systems within the Mississippi River basin associated with the Interior Highlands of midwestern North America. An additional haplotype network analysis also supported these trends. Phylogenetic divergence dating indicated that population separation between the river systems occurred after recent Pleistocene glacial events rather than an early Pleistocene separation.

Fishes As A Template For Reticulate Evolution: A Case Study Involving Catostomus In The Colorado River Basin Of Western North America, Max Russell Bangs

Graduate Theses and Dissertations

Hybridization is neither simplistic nor phylogenetically constrained, and post hoc introgression can have profound evolutionary effects. Most studies have focused on tractable model systems, rather than organisms with complicated phylogenetic histories. Finescale Sucker (genus Catostomus) in western North America is recognized as a paradigm of fish hybridization. Yet, its extent of historic and contemporary introgression is largely unstudied, an aspect that impedes the resolution of its phylogeny as a baseline for conservation. To explore reticulation in this group, I assayed variation of 20 Catostomus species across temporal and geographic scales by analyzing hundreds of samples and employing a combination of …

Estimating The Frequency Of Sexual Reproduction In The Diatom Stephanodiscus Niagarae, Ann W. Dickens

Biological Sciences Undergraduate Honors Theses

Diatoms are single-celled micro-algae with cell walls composed of silica, that reproduce in a way that results in a decrease in cell size after each round of mitotic (asexual) division. A cell cannot continue to shrink indefinitely, so when the average size of the population reaches a critical threshold, diatoms reproduce sexually and restore their maximal size. It is unclear, however, how frequently diatoms undergo sexual reproduction in nature. As a proxy for sexual reproduction, I monitored changes in cell size of a population of the diatom Stephanodiscus niagarae from the plankton community of Lake Fayetteville (Arkansas, USA). Weekly sampling …

Management Of A Primordial Problem: Redox-Sensitive Transcriptional Regulation In Methanosarcina Acetivorans, Ryan Christopher Sheehan

Graduate Theses and Dissertations

The primordial Earth which hosted the first forms of life was an environment free of oxygen. Early organisms utilized metabolisms dependent upon anaerobic conditions and incorporated systems to which oxygen is deleterious. As the content of oxygen in Earth's atmosphere increased, anaerobic organisms had to acquire methods to sense and combat oxygen and reactive oxygen species. Several mechanisms were advantageous to such anaerobic organisms which correlated transcriptional processes with the redox state of the cell so that energy may be conserved and oxygen stress recovery genes activated during periods of oxidative stress. Iron sulfur (Fe-S) cluster cofactors incorporated within RNA …

The Reproductive Ecology Of The Timber Rattlesnake, Crotalus Horridus, In Northwestern Arkansas: Interactions Between Environment, Steroid Hormones, And Life History, Craig Michael Lind

Graduate Theses and Dissertations

In this dissertation I examined the relationship between individual energetic status, hormone production, and life history trait expression in field-active Timber Rattlesnakes, Crotalus horridus. In chapter one I reviewed what is known regarding these relationships in snakes and defined major research goals. In chapter two I described the seasonal profile of testosterone (T) and corticosterone (CORT) in relation to the breeding season and to individual energetic status in males. Results showed that the seasonal pattern of T production in C. horridus was different than other pit viper species with similar mating patterns. Testosterone was elevated in the months leading up …

Transcriptomic Insights Into The Diplontic Life History Of Diatoms, Colton Richard Kessenich

Graduate Theses and Dissertations

An organism's life cycle is the direct result of its evolutionary history and represents a fundamental aspect of its ancestry and ecology. Yet the process of linking alternating life-history stages has proven to be challenging, if not impossible in some cases. Diatoms (Bacillariophyceae) are no exception to this challenge, and their diversity of life stages and reproductive strategies add further challenges. A central focus of diatom research has been to unravel the evolutionary events that led to their extraordinary diversity, a line of inquiry that has been greatly aided by the availability of next-generation sequence data. Yet without proper taxonomic …

Phenotypic Plasticity Of Rattlesnake Trophic Morphology, Matthew Thomas Smith

Graduate Theses and Dissertations

The trophic morphology of gape-limited predators constrains the shape and size of prey items they can ingest. Trophic morphology consists of any morphological feature that is involved in the handling and ingestion of food. Diet has a profound effect on the morphology of many gape-limited predators. Identifying how prey type and resource level affect the morphology of different populations is an essential step in understanding the mechanisms contributing to patterns of morphological diversity. Species interactions (Chapter 1) induce plasticity in morphology that can lead to increased fitness, morphological divergence, and eventually speciation.

In Chapter 2, a laboratory study tested the …

Letter From The Dean, Lalit Verma

Discovery, The Student Journal of Dale Bumpers College of Agricultural, Food and Life Sciences

No abstract provided.