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Articles 1 - 10 of 10
Full-Text Articles in Genetics and Genomics
Effects Of Riverine Barriers On Avian Evolution In The Amazon Basin, Andre Eugene Moncrieff
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, …
Insights Into The Speciation Process From Genomic And Phenotypic Analysis Of An Avian Hybrid Zone In Amazonia, Glaucia Christina Del-Rio
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. …
Genetic Structuring And Community Assembly In Neotropical Birds, Oscar Johnson
Genetic Structuring And Community Assembly In Neotropical Birds, Oscar Johnson
LSU Doctoral Dissertations
The factors that influence how species form is of fundamental interest to biology. Under the framework of the speciation cycle, the process begins by population subdivision creating structured populations that then diverge until two new species form. Following speciation, however, continued divergence is necessary for these new species to be able to coexist without adverse interactions, known as the transition to secondary sympatry. At this point the speciation cycle is complete and the process can begin anew. Many of the factors influencing these processes remain poorly understood. Here, I explore the factors that influence speciation and community assembly in Neotropical …
Leveraging Multiple Data Sources: How Catch Data, Metadata, And Genetic Samples Can Aid The Recovery Of Endangered Smalltooth Sawfish (Pristis Pectinata), Kelcee Smith
LSU Doctoral Dissertations
The small population sizes characteristic of many imperiled species means that they are vulnerable to both demographic and genetic extinction threats. Responses to these threats (e.g., population trends, genetic diversity estimates) are often difficult to obtain, but critical for conservation. Thus, researchers studying imperiled species may have to consult multiple data sources, collaborate with a wide variety of stakeholders, or ask new questions about previously collected data. I used this approach to understand more about the United States (U.S.) population of Pristis pectinata, an endangered elasmobranch that has declined up to 95% due to habitat loss and bycatch in …
Micro- And Macroevolution Of Drab Plumage Color In Birds, Rafael Marcondes
Micro- And Macroevolution Of Drab Plumage Color In Birds, Rafael Marcondes
LSU Doctoral Dissertations
I address the evolution of drab bird colors at micro- and macroevolutionary scales. I use as a study system the Furnariida, a clade of >600 Neotropical passerine species that, despite tremendous ecological and morphological diversity, are colored almost exclusively in shades of brown and grey produced by melanin pigments.
In chapters two and three, I took a macroevolutionary approach and showed that (1) plumage colors in the Furnariida evolve at similar rates in a monochromatic clade, males of a dichromatic clade, and females of a dichromatic clade; (2) ventral plumage color evolves faster than dorsal; (3) bird species that occupy …
Quantifying Structure And Variation In Complex Phylogenetic Data, Genevieve Geraldine Mount
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 …
The Evolution Of Bivalve Shell Matrix Proteins, Mark Ira Duhon Ii
The Evolution Of Bivalve Shell Matrix Proteins, Mark Ira Duhon Ii
LSU Doctoral Dissertations
This dissertation focuses on the molecular underpinnings surrounding the evolution of the biomineralized shells of marine bivalves. Bivalve molluscs synthesize remarkably complex shells from calcium carbonate and an organic matrix of proteins secreted from the dorsal edge of the mantle. Molecular analyses of shell matrix proteins (SMPs) have suggested high rates of gene turnover despite the conserved nature of the shell itself. Here, I used proteomic and transcriptomic data to identify the SMPs and other biomineralization proteins from seven bivalve species that diverged 3-513 Mya. Contrary to previous studies that identified only a few shared biomineralization transcripts across the Bivalvia, …
Natural Variation And Evolutionary Responses To Climate Change Stressors In Marine Invertebrates, Joanna Sarah Griffiths
Natural Variation And Evolutionary Responses To Climate Change Stressors In Marine Invertebrates, Joanna Sarah Griffiths
LSU Doctoral Dissertations
Our rapidly changing climate is putting many species at risk of extinction and there is an urgent need to understand how species will respond to these changes. In this dissertation, I evaluate how three species of marine invertebrates (corals, oysters, and copepods) respond to stressful conditions in their current environments and how plasticity and evolutionary adaptation could alter their response to future climate change stressors. I first employed a space for time study to elucidate population differences in the response of cold-water corals, Balanophyllia elegans, to future ocean acidification. I found evidence that upwelling history (natural low pH exposure) influences …
Speciation And Hybridization In Jamaican-Endemic Streamertail Hummingbirds (Trochilus Polytmus And T. Scitulus), Caroline D. Judy
Speciation And Hybridization In Jamaican-Endemic Streamertail Hummingbirds (Trochilus Polytmus And T. Scitulus), Caroline D. Judy
LSU Doctoral Dissertations
Streamertails hummingbirds (Trochilus polytmus and T. scitulus) are recently diverged sister taxa that appear to have speciated in situ on the island of Jamaica. They are distinguished by male bill color, a secondary sexual trait that is coral red in T. polytmus and jet black in T. scitulus. They hybridize in a narrow zone where their ranges meet in eastern Jamaica. In Chapter 2, I performed a formal population survey of T. scitulus to determine the size of the population, which was unknown. I determined that the total population contains well over 100,000 individuals despite its limited …
Computational Analysis Of Papionini Evolution Using Alu Insertions, Vallmer Edward Jordan Ii
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 …