Life Sciences Commons^™

Leveraging Morphological And Phylogenomic Methods To Elucidate The Evolution Of Dixidae, Jackson H. Turner

Masters Theses

Dixidae is an obscure family of Diptera with highly cryptic morphologies and a confused evolutionary history. An intrafamily systematic review is thus far unattempted and existing generic concepts are currently untested through molecular methods. 2261 Nuclear orthologs and 13 mitochondrial coding sequences were leveraged to create ML phylogenies for this family. Phylogenies created from both datasets are highly concordant with one another. The results herein support the existing phylogenetic placements of the three most robust genera (Dixa, Dixella, Nothodixa) but two were found to be highly nested (Asiodixa nested within Dixella and Meringodixa nested within Dixa). …

Species Delimitation Of Slimy Salamanders, Plethodon Kisatchie And Plethodon Mississippi, Across The Lower Mississippi River, Brock Hunter Stevenson

Master's Theses

Species are fundamental units of biodiversity yet delimiting species can be challenging. Slimy Salamanders of the Plethodon glutinosus species complex are a classic example of cryptic species for which species boundaries and relationships have proved difficult to determine. Once thought to be a single species ranging across the eastern United States, protein analysis revealed high genetic divergences among geographically distinct groups of populations, leading to 16 species being recognized within the group. Two of these species, the Louisiana Slimy Salamander (Plethodon kisatchie) and the Mississippi Slimy Salamander (Plethodon mississippi), are closely related but occur on opposite sides of the Mississippi …

Placing The Evolutionary History Of Desmognathus Salamanders In Context: A Phylogeographic Approach, Kara Jones

Theses and Dissertations--Biology

Patterns of genetic variation do not arise in a vacuum but are instead shaped by the interplay between evolutionary forces and ecological constraints. Here, I use a phylogeographic approach to examine the role that ecology played in lineage divergence in the Desmognathus quadramaculatus species complex (Family: Plethodontidae), which consists of three nominal species: D. quadramaculatus, D. marmoratus, and D. folkertsi. Previous phylogenetic studies have shown that individuals from these species do not form clades based on phenotype. My approach to reconciling phylogenetic discordance was two-fold, using (1) genome-wide markers to provide insight into the …

Comparative Genomics Methods And Applications, Emily N. Alden

Biomedical Sciences ETDs

Virtually all fields of biology have benefited from the advancements in comparative genomics technologies, specifically in the study of evolution. In this dissertation I develop and use comparative genomic technologies to investigate the novel SARS-CoV-2 virus, assembly the first genome of the black lace domestic angelfish and identify germline genetic variants associated with altered breast cancer-specific survival. Our genome tiling array for the novel coronavirus presents a rapid and cost-effective method to sequence the entire viral genome and can be used to track the rapid evolution of viral variants in the population. The domestic angelfish is a member of the …

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 …

Quantifying Structure And Variation In Complex Phylogenetic Data, Genevieve Geraldine Mount

LSU Doctoral Dissertations

Identifying the source and structure of variation in nature is crucial to understanding fundamental aspects of evolution. Despite a recent plethora of genetic and morphological data, many interesting questions about the relationships between different groups remain unresolved. My dissertation evaluates three approaches for identifying and quantifying the variation within phylogenetic datasets. Characterizing variation within datasets and across analytical methods gives insight into biologically interesting characters, unusual evolutionary processes, and areas for model improvement.

Network-based community detection approaches offer a powerful tool to describe variation in phylogenetic signal across the genome (i.e., gene tree variation). In Chapter 2, I investigate the …

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 …

The Sucking Louse Fauna Of Mongolian Rodents: Host Associations, Molecular Phylogenetics And Description Of Two New Species, Chase N. Robinson

Honors College Theses

This study aimed to screen Mongolian rodents for sucking lice (Insecta: Phthiraptera: Anoplura) to better understand host-parasite associations for this understudied region. Nine species, including 3 previously undescribed, from 4 genera were identified. A molecular phylogeny based on 2 mitochondrial genes of collected louse specimens is included.

Phylogenetic History Of The Amy Gene Cluster In Catarrhines, Christian M. Gagnon

Theses and Dissertations

This study phylogenetically analyzed 30 AMY-related genes from 11 primates. The results show the gradual expansion of the AMY gene family which could have allowed primates to adapt to various ecological landscapes and maximize energy intake from starch-rich foods in periods of food scarcity.

Population Structure, Demographic History, And Environmental Niche Of The Sand Fly Disease Vector Lutzomyia Shannoni (Dyar) (Diptera: Psychodidae) In The U.S., Mexico, And Colombia, Matthew E. Wolkoff

Biology Theses

Lutzomyia shannoni (Dyar, 1929) (Diptera: Psychodidae) is the only known sand fly vector of vesicular stomatitis virus, a putative leishmaniasis vector, and also boasts the widest distribution of any sand fly in the New World. Research on Lu. shannoni in Central and South America has revealed genetically divergent subpopulations; however, tentative analysis of Lu. shannoni in the U.S. has failed to detect any significant population structure, even between specimens collected from highly disparate localities.

The present study used four molecular markers to more closely investigate the population structure of Lu. shannoni in the U.S., and assess the species’ relationships with …

Diversity And Distribution Of Diatom Endosymbionts In Amphistegina Spp. (Foraminifera) Based On Molecular And Morphological Techniques, Kwasi H. Barnes

USF Tampa Graduate Theses and Dissertations

Diatoms associated with foraminifers of the genus Amphistegina were assessed using a combination of morphological and molecular techniques. These included: 1) microscopic identification of diatoms cultured from the host, 2) sequencing of portions of the small subunit of the ribosomal RNA gene (18S) and the large subunit of the ribulose-1,5-bisphosphate carboxylase/oxygenase [i.e., RubisCO] gene (rbcL) from DNA extracted directly from the Amphistegina hosts and also from diatoms cultured from these hosts, and 3) denaturing gradient gel electrophoresis (DGGE) profiles of rbcL and internal transcribed spacer 1 (ITS1) PCR amplicons from DNA extracted directly from …