Evolution Commons^™

Intermediates Or Intermedius? An Examination Of Lotic Sternotherus In Baldwin And Mobile Counties, Al, Peyton A. Wilson

Theses

The Southeastern United States is a biodiversity hotspot, and turtles are no exception to the rule. This is particularly true for the genus Sternotherus. Alabama is the only state home to all six species of Sternotherus, including the recently described Intermediate Musk Turtle (Sternotherus intermedius). It was thought that the Perdido River was the western boundary of Sternotherus intermedius; however, surveys in recent years produced questionable individuals in several small watersheds feeding into the Mobile-Tensaw Delta, bringing the species true range into question, as well as the question of if this species has hybridized with its congener, …

Population Genetic Diversity In Two Biological Systems, Alyson Emery

Electronic Theses and Dissertations

Population genetic analysis can be used to answer questions about population structure and composition in many biological systems. Recent improvements to sequencing technologies have made population genetic studies more accessible than ever before. Many of the same techniques can be applied to different biological systems, but some analyses may differ depending on how genetically divergent the populations in question are. Here, we describe two unique projects using next-generation genome sequencing, each looking at population structure at different levels of genetic divergence: the first involved determining interspecific population structure between two species of hybridizing field cricket using a novel sequencing method, …

Co-Divergence Of Lemur Hosts And Gut Microbiomes Across Multiple Evolutionary Scales, Mariah E. Donohue

Theses and Dissertations--Biology

This dissertation bridges micro- and macroevolutionary approaches to understand the co-diversification of animal hosts and their gut microbiomes at different evolutionary timescales. I examined these dynamics using wild lemurs, a diverse Primate clade endemic to the island of Madagascar.

First, I tested the relative effects of host phylogenetic relationships, diet, and habitat in shaping the gut microbiome through deep evolutionary time and across distinct microbial kingdoms. I designed a natural experiment sampling feces from rainforest and dry forest lemur communities with similar phylogenetic assemblages and considerable variation in dietary strategy. Then, I amplified and sequenced two metabarcoding genes, the V4 …

Reproductive Isolation And Gene Flow Across Space, Time And Genomes In Neodiprion Lecontei And N. Pinetum, Ashleigh Nicole Glover

Theses and Dissertations--Biology

To explain biodiversity, evolutionary biologists must understand how independent lineages arise via the evolution of reproductive isolation during the speciation process. Hybridizing taxa provide an excellent opportunity to investigate the evolution of reproductive isolating barriers and genomic divergence, thereby enhancing our understanding of speciation. However, hybridization between diverging taxa can vary across geographic space, the genome, and time. Thus, understanding the factors that promote or inhibit hybridization can provide insight into the biotic, environmental, and genetic causes of divergence and gene flow. Importantly, the mechanisms responsible for generating variation in hybridization dynamics and the consequences of such hybridization remains unknown …

The Evolutionary Causes And Consequences Of Mammalian Hybridization, Kelsie E. Hunnicutt

Electronic Theses and Dissertations

The natural recombination of divergent genomes within hybrid offspring provides windows through which we can study evolutionary processes and the dynamics of speciation. In this work, I use a combination of comparative and population genomics on both laboratory crosses of divergent rodent lineages and a hybrid zone of cottontail rabbits in the wild to study the causes and consequences of hybridization in mammals. Hybrid sterility is a common reproductive barrier between species that tends to preferentially manifest in the heterogametic sex and frequently genetically maps to the sex chromosomes. Thus, the sex chromosomes appear to play a special role in …

Quantitative Song Variety In Relation To Genotype In A Hybridizing Chickadee Population, Shelby Madison Palmer

Graduate Theses/Dissertations

The Black-capped chickadee (Poecile atricapillus) and Carolina chickadee (P. carolinensis) are North American songbird species that hybridize in a narrow contact zone stretching latitudinally from New Jersey to Kansas, USA. The association between genetic ancestry and song type in this hybrid zone has been studied independently several times and found to be minimal or absent, likely due to the influence of cultural transmission on learned song in the oscine passerine clade to which the chickadees belong. Despite this, the song of both species remains remarkably distinct in allopatry, suggesting a genetic constraint on certain qualities of …

Effects Of Riverine Barriers On Avian Evolution In The Amazon Basin, Andre Eugene Moncrieff

LSU Doctoral Dissertations

The high biodiversity found in the Amazon Basin has long captivated the attention of naturalists and evolutionary biologists seeking to explain its origins. Early observations by Alfred Wallace highlighted the role of rivers in delimiting the geographic ranges of many species; furthermore, where rivers narrow towards their headwaters, he noted that some species cross rivers freely. A major goal of this dissertation is to investigate how these and other observations about riverine barriers might inform our understanding of how speciation unfolds in Amazonia. My approach involved generating genomic data with dense geographic sampling for manakins in the genus Lepidothrix, …

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 …

Insights Into The Speciation Process From Genomic And Phenotypic Analysis Of An Avian Hybrid Zone In Amazonia, Glaucia Christina Del-Rio

LSU Doctoral Dissertations

Understanding the outcome of secondary contact is essential to shed light on the mechanisms governing species formation and maintenance. In Amazonia, closely related bird taxa with limited dispersal abilities are often separated by rivers, which presumably act as dispersal barriers. However, at the headwaters, rivers cease to be dispersal barriers, and this generates opportunities for secondary contact. In my dissertation, I studied genomic mechanisms associated with phenotypic differences, mitochondrial DNA structure, and putative reproductive barriers between two hybridizing Amazonian bird species in the genus Rhegmatorhina, a group of antbirds that find their arthropod prey exclusively by following army-ant swarms. …

Comparing The Reproductive Fitness Of Fundulus Hybrids And Their Parental Species (Fundulus Olivaceus And Fundulus Notatus) Within Mississippi Freshwater Contact Zones, Sarah Stovall

Honors Theses

Hybridization of closely related taxonomic groups within the Animal Kingdom has led to complex species interactions that are not well understood. Pre-zygotic or post-zygotic barriers complicate hybridization as a means to diversify; however, diverging hybrids may speciate and expedite evolution of involved taxa. This study pursues understanding of these intricate interactions using topminnow Fundulus notatus, Fundulus olivaceus, and their hybrids from the Fundulus notatus species complex. Persisting hybrids within riverine contact zones were hypothesized to experience barriers of hybrid breakdown from lower fitness in comparison to the pure species. Specimens were collected within four contact zones: Spring River, …

Reproduction And Parasite-Mediated Selection, Meredith A. Krause

USF Tampa Graduate Theses and Dissertations

Sexual reproduction generates genetic diversity that can help hosts respond to selection by parasites, and in this thesis, I test three predictions on how reproduction impacts predictions by the parasite theory of sex and the Red Queen hypothesis. In Chapter one, using a meta-analysis, I found that asexuals (lower genetic diversity) have more parasites than sexuals (higher genetic diversity), but this difference can be heavily mediated by the mode and origin of asexuality. Further, hybridization but not polyploidy can blunt predicted differences in parasite loads among sexual and asexual hosts. In Chapter two, I flip the perspective of Red Queen …

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 …

Interspecific Gene Flow Potentiates Adaptive Evolution In A Hybrid Zone Formed Between Pinus Strobiformis And Pinus Flexilis, Mitra Menon

Theses and Dissertations

Species range margins are often characterised by high degrees of habitat fragmentation resulting in low genetic diversity and higher gene flow from populations at the core of the species range. Interspecific gene flow from a closely related species with abutting range margins can increase standing genetic diversity and generate novel allelic combinations thereby alleviating limits to adaptive evolution in range margin populations. Hybridization driven interspecific gene flow has played a key role in the demographic history of several conifer due to their life history characteristics such as weak crossability barriers and long generation times. Nevertheless, demonstrating whether introgression is adaptive …

A Taxonomic Revision Of The Genus Burmeistera (Campanulaceae) In Ecuador, Brock Mashburn

Theses

The genus Burmeistera (Campanulaceae) consists of approximately 120 species of herbaceous trailing shrubs, found mostly in cloud forests from Guatemala to Peru. Taxonomic work is difficult for the genus because of its relatively recent diversification (5–12 mya) and the morphological lability of its species. The last monograph for the genus was completed in 1943, followed periodically by country-level treatments. For Ecuador, the most recent treatment of Burmeistera was nearly 40 years ago, in Stig Jeppesen’s 1981 treatment in the Flora of Ecuador. Jeppesen’s treatment recognized 32 species and subspecies. Since then, nine new species have been described and hundreds of …

Computational Analysis Of Papionini Evolution Using Alu Insertions, Vallmer Edward Jordan Ii

LSU Doctoral Dissertations

Alu elements are primate specific retrotransposons that have remained active throughout the course of primate evolution. As a result of this sustained mobilization. Alu elements are present in greater copy number in primate genomes than any other transposable element. An average of over one million Alu elements has been identified in every sequenced haplorrhine genome to date. These characteristics qualify Alu elements as ideal characters for studying evolutionary relationship among primates.

The increasing availability of whole genome sequencing data presents novel challenges and opportunities for comparative genomic analyses. Genomic data is now publicly available for most primate species. Such an …

Genetic Differentiation Between Two Species Of Buckwheat (Eriogonum), Paul G. Wolf, Jenessa B. Lemon

Browse all Datasets

Discovering the extent of genetic differentiation between closely related taxa facilitates decisions regarding species protection under the Endangered Species Act. Here, we analyze genotype data to explore the relatedness of two buckwheat species: Eriogonum soredium Reveal- a narrow endemic under consideration for protection, and a widespread close relative, Eriogonum shockleyi S. Watson. Eriogonum soredium grows only on Ordovician limestone outcroppings in west central Utah, whereas the range of E. shockleyi is broad, spanning the western United States from Colorado to California, and Idaho to Arizona. Eriogonum shockleyi is suspected of hybridizing with other buckwheats throughout this range. We detected higher …

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 …

Polymorphism And Hybridization In Species Of Hottentotta Birula, 1908 (Scorpiones: Buthidae), Wilson R. Lourenço, Eric Ythier, Mark Stockmann, John L. Cloudsley-Thompson

Euscorpius

A new and well documented case of hybridization among scorpions is presented. It was obtained under laboratory conditions between Hottentotta jayakari (Pocock) and Hottentotta salei (Vachon) specimens of which had been collected in the northern and southern regions of Oman. Hybrids were successfully produced not only from F₀ males and females, but also from F₁ males and females, thereby attesting to the fact that the first generation obtained (F₁), was completely fertile. Both F₁ and F₂ broods were composed of dark and pale morphs, indicating that the juveniles could inherit either one or …

Multilocus And Parametric Analyses Of The Evolutionary History Of The Amazonian Peacock Cichlids, The Genus Cichla (Teleostei: Cichlidae), Stuart Clayton Willis

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

Accurate knowledge of species boundaries and species phylogeny are fundamental to testing hypotheses of recent evolutionary processes, but the estimation of these partitions is challenging due both to inherent confusion about what is being estimated as well as the data available to estimate them. Using multilocus data from mtDNA, microsatellites, and nuclear locus sequences of over 1100 individuals, we delimited eight separately evolving species of Cichla rather than the 15 described. Among species we found evidence of rare but widespread introgressive hybridization, while within these species we observed evidence of long-term gene exchange and constrained evolutionary trajectories. In most cases …

Assessing Genetic Differentiation Among Populations Of The Invasive Plant Impatiens Glandulifera In Maine, Jordan R. Schoonover

Honors Theses

The annual herbaceous plant Impatiens glandulifera Royle is native to the Himalayas and is a significant invasive species in Europe. In the past century, it was introduced to the United States, where it has become established in 12 states. This study evaluated genetic differentiation among four Maine populations, to address a theory that posits hybridization of distinct lineages as a trigger for invasiveness. Regions of microsatellite repeats were evaluated at two polymorphic loci for 41 plants sampled from the four populations. A striking finding was that the observed heterozygosity was substantially higher than the heterozygosity expected from random combination of …