Open Access. Powered by Scholars. Published by Universities.®
- Institution
Articles 1 - 9 of 9
Full-Text Articles in Entire DC Network
Dynamics Of Avian Elevational Ranges Reveal Hidden Evolutionary Forces, Chauncey Gadek
Dynamics Of Avian Elevational Ranges Reveal Hidden Evolutionary Forces, Chauncey Gadek
Biology ETDs
The distribution of life across the Andes mountains reflects historical elevational-range contraction and expansion. Whereas contraction implies specialization, expansion requires overcoming hidden barriers. Three eco-evolutionary phenomena may drive patterns in rates of elevational range evolution: (1) The Dobzhansky-MacArthur Phenomenon (DMP) predicts lower rates of upward expansion with harsher physical conditions, while downward expansion increases with lower diversity; (2) the evolutionary tendency toward specialization predicts contraction increases when ranges are broad; and (3) natural selection for respiratory performance could suppress expansion across mid-elevations due to gene-environment mismatch. We modeled elevational range shifts of Neotropical landbirds. Contrary to the DMP, upward expansion …
The Functional, Ecological, And Evolutionary Morphology Of Sea Lampreys (Petromyzon Marinus), Bradley Morgan Wood
The Functional, Ecological, And Evolutionary Morphology Of Sea Lampreys (Petromyzon Marinus), Bradley Morgan Wood
LSU Doctoral Dissertations
Lampreys (Petromyzontiformes) are jawless vertebrates with an evolutionary history lasting at least 360 million years and are often used in comparisons with jawed vertebrates because some of their morphological aspects, such as the segmented trunk musculature with curved myosepta and a non-mineralized skeleton fibrous skeleton, are thought to resemble the condition of early vertebrates before the evolution of jaws. Although earlier authors studied the morphology of the skeleto-muscular system of the trunk of lampreys, their studies are not detailed and complete enough to allow a functional and biomechanical analysis that is needed as a basis for modeling the mechanics of …
Comparative Brain Anatomy Of Lamniform Sharks (Elasmobranchii: Lamniformes) And Its Implications To Function, Behavioral Ecology, And Evolution, Francesco Guzzo
Comparative Brain Anatomy Of Lamniform Sharks (Elasmobranchii: Lamniformes) And Its Implications To Function, Behavioral Ecology, And Evolution, Francesco Guzzo
College of Science and Health Theses and Dissertations
Understanding the diversity of brain morphology is important to understand the evolution of cognitive ability and how ecology and phylogeny have influenced the variation in brain complexity. I examined the morphological variation of the brain in the shark order Lamniformes based on museum specimens and literature. Where I illustrate a wide range of morphological diversity in lamniform brains, my study shows that there is a strong positive correlation between brain size and body size that sharks with a larger brain tend to have a more foliated cerebellum, but that the body weight over brain weight did not correlate with cerebellar …
Quantifying The Predictability Of Evolution At The Genomic Level In Lycaeides Butterflies, Samridhi Chaturvedi
Quantifying The Predictability Of Evolution At The Genomic Level In Lycaeides Butterflies, Samridhi Chaturvedi
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
Stephen Jay Gould, a great scientist and evolutionary biologists, suggested that if we could replay the tape of life, we would not have observed similar course of events because evolution is stochastic and if affected by several events. Since then, the possibility that evolution is repeatable or predictable has been debated. Studies using large-scale evolution experiments, long-term data for individual populations, and controlled experiments in nature, have demonstrated phenotypic and genetic convergence in several taxa. These studies suggest that despite some randomness, predictable evolutionary patterns can emerge on a large temporal and spatial scale. However, a few cases also exist …
Mixing It Up: The Impact Of Episodic Introgression On The Evolution Of High-Latitude Mesocarnivores, Jocelyn P. Colella
Mixing It Up: The Impact Of Episodic Introgression On The Evolution Of High-Latitude Mesocarnivores, Jocelyn P. Colella
Biology ETDs
At high latitudes, climatic oscillations have triggered repeated episodes of organismal divergence by geographically isolating populations. For terrestrial species, extended isolation in glacial refugia – ice-free regions that enable terrestrial species persistence through glacial maxima – is hypothesized to stimulate allopatric divergence. Alternatively, upon glacial recession, divergent populations expanded from independent glacial refugia and often contacted other diverging populations. In the absence of reproductive isolating mechanisms, this biogeographic process may trigger hybridization and ultimately, gene flow between divergent taxa. My dissertation research aims to understand how these episodic periods of isolation and contact have impacted the evolution of high latitude …
Body Forms In Sharks (Chondrichthyes: Elasmobranchii), And Their Functional, Ecological, And Evolutionary Implications, Phillip C. Sternes
Body Forms In Sharks (Chondrichthyes: Elasmobranchii), And Their Functional, Ecological, And Evolutionary Implications, Phillip C. Sternes
College of Science and Health Theses and Dissertations
Sharks are among the oldest vertebrate lineages in which their success has been attributed to their diversity in body shape and locomotor design. In this study, I investigated the diversity of body forms in extant sharks using landmark-based geometric morphometric analyses on lateral view illustrations of nearly all the known (ca. 470) extant sharks in a published guidebook. I ran three different analyses: the ‘full body,' ‘precaudal body,’ and ‘caudal fin' analyses. My study suggests that there are two basic body forms in sharks. The two major body forms are characterized as a ‘shallow-bodied’ form (Group A) and ‘deep-bodied’ form …
Reproductive Character Displacement In Calopteryx Aequabilis And C. Maculata: Improving Species Recognition Through The Divergence Of Male Mating Preferences, Melissa Encinias
Reproductive Character Displacement In Calopteryx Aequabilis And C. Maculata: Improving Species Recognition Through The Divergence Of Male Mating Preferences, Melissa Encinias
Masters Theses, 2010-2019
An ongoing evolutionary question is how co-occurring species maintain reproductive barriers when they are morphologically, behaviorally, and ecologically similar. Without geographic isolation, traits involved in species recognition may be under selection to enhance reproductive barriers. Exaggerated trait differences between species in sympatric populations may reflect selection to reduce misdirected mating between species, or reproductive character displacement. While this phenomenon is widely recognized as an important stage in the speciation process, there is little direct evidence of this process in nature. In two North American damselfly species, Calopteryx aequabilis and C. maculata, wing pigmentation is sexually dimorphic and also shows …
Multispecies Character Displacement In Mexican Poeciliopsis Fishes, Andrea J. Roth
Multispecies Character Displacement In Mexican Poeciliopsis Fishes, Andrea J. Roth
Theses and Dissertations
Competition has long been recognized as a central force in shaping evolution, particularly through character displacement. Yet research on character displacement is biased as it has focused almost exclusively on pairs of interacting species while ignoring multispecies interactions. Unfortunately, communities are seldom so simple that only pairs of species interact, and it is not clear if inferences from pairwise interactions are sufficient to explain patterns in nature. A more realistic approach is to ask how traits evolve when multiple species interact. Here I explore the importance of multispecies competitive interactions on trait evolution in four congeneric species of livebearing fishes …
Phylogeography Of The Neotropical Fish Genus Rhoadsia (Teleostei: Characidae) In Ecuador, Roberto Valentino Cucalón Tamayo
Phylogeography Of The Neotropical Fish Genus Rhoadsia (Teleostei: Characidae) In Ecuador, Roberto Valentino Cucalón Tamayo
College of Science and Health Theses and Dissertations
Western Ecuador is considered a biodiversity hotspot. Nevertheless, studies of population genetic structure and variation are rare, especially in aquatic species. The genus Rhoadsia is an endemic freshwater fish in this region with two recognized species, Rhoadsia minor and R. altipinna. Little is known about the evolutionary relationships of their populations, and due to morphological similarities, their validity as distinct species has been questioned. The present study uses a phylogeographic approach to examine the evolutionary history of the genus and the validity of the two described species. Furthermore, I investigated the possible geographical origin of the genus based on patterns …