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Articles 1 - 10 of 10
Full-Text Articles in Life Sciences
Morphological And Gene Expression Plasticity In Neotropical Cichlid Fishes, Sharon Fern Clemmensen
Morphological And Gene Expression Plasticity In Neotropical Cichlid Fishes, Sharon Fern Clemmensen
Doctoral Dissertations
Trophic divergence in cichlid fish is linked to morphological shifts in the pharyngeal jaw apparatus. For instance, in the Heroine cichlids of Central America, the ability to crush hard-shelled mollusks is a convergent phenotype with multiple evolutionary origins. These durophagous species often have very similar pharyngeal jaw morphologies associated with the pharyngeal jaw apparatus and some of these similarities could be due to phenotypically plastic responses to mechanical stress. I examined the durophagous cichlid Vieja maculicauda for differences in pharyngeal osteology, dentition, and soft tissues when exposed to different diet regimes. Here I discuss the effect on the morphology and …
Systematics And Biogeography Of The Cortinarius Violaceus Group And Sequestrate Evolution In Cortinarius (Agaricales), Emma Harrower
Systematics And Biogeography Of The Cortinarius Violaceus Group And Sequestrate Evolution In Cortinarius (Agaricales), Emma Harrower
Doctoral Dissertations
Phylogenetics is a powerful tool used for illuminating the diversity of life on Earth, their evolution and their ecology. I created a multi-gene phylogenetic tree of Cortinarius section Cortinarius and uncovered five previously overlooked species, increasing the number of species in the section from seven to twelve. All members of the clade possess both cheilocystidia and pleurocystidia and possess a pigment known as (R)-39,49-dihydroxybphenylalanine. Ancestral state reconstruction estimated that the ancestral host was most likely an angiosperm, switching hosts when encountering novel host species in new lands, and only C. violaceus associating with the Pinaceae in North America. Biogeographic analysis …
All Roads Lead To Weediness: Stories About Weedy Rice Origins, Weedy Genes And Weed Competitiveness, Zhongyun Huang
All Roads Lead To Weediness: Stories About Weedy Rice Origins, Weedy Genes And Weed Competitiveness, Zhongyun Huang
Doctoral Dissertations
Weedy rice (Oryza spp.), a weedy relative of cultivated rice (O.sativa), infests and persists in cultivated rice fields worldwide. Many weedy rice populations have evolved similar adaptive traits, considered part of the ‘agricultural weed syndrome’, making this an ideal model to study the genetic basis of parallel evolution. Using population genetics analyses of South Asian and US weedy rice, my research reveals multiple independent evolution events giving rise to weed groups in the two geographic areas. Weeds in South Asia have highly heterogenous genetic backgrounds, with contributions from both cultivated varieties (aus and indica) …
The Role Of Phenotypic Integration In Mammalian Tooth Function And Jaw Morphological Diversity, Andrew Conith
The Role Of Phenotypic Integration In Mammalian Tooth Function And Jaw Morphological Diversity, Andrew Conith
Doctoral Dissertations
Here I investigate how two major components of the mammalian feeding system, teeth and jaws, are influenced by functional, environment, and developmental factors. First, I build physical models of the molars from two early mammals, Morganucodon and Kuehneotherium, and compare their ability to process a proxy food item. Early mammals were under strong selection to reduce metabolic costs, so any savings in energy during feeding would be advantageous. I tested the ability of both mammals to process a hard and soft food item with material properties similar to that of the insects they would have likely consumed. Morganucodon was …
Burrowing And Walking Mechanisms Of North American Moles, Yi-Fen Lin
Burrowing And Walking Mechanisms Of North American Moles, Yi-Fen Lin
Doctoral Dissertations
Moles (Family Talpidae) are a classic example of extreme specialization, in their case highly derived forelimb morphologies associated with burrowing. Despite many observations of mole burrows and behaviors gathered in the field, we know very little about how and how well moles use their forelimbs to dig tunnels and to walk within the built tunnels to collect and transport food. The first chapter investigates the effect of soil compactness on two sympatric mole species under controlled laboratory conditions. My results demonstrate that increasing soil compactness impedes tunneling performance as evidenced by reduced burrowing speed, increased soil transport, shorter tunnels, shorter …
Systematics, Diversification, And Functional Diversity Of Russulaceae (Russulales), Brian Patrick Looney
Systematics, Diversification, And Functional Diversity Of Russulaceae (Russulales), Brian Patrick Looney
Doctoral Dissertations
The family Russulaceae is an iconic family of mushroom-forming Basidiomycetes both because of their importance as edible mushrooms in many parts of the world and their species richness in both temperate and tropical forested biomes. While much mycological research has been focused on this group, recent systematic and ecological research has failed to develop a comprehensive or cohesive organization by which to understand the evolutionary relationships, patterns of diversification, or functional importance of the group. Recently, interest in ectomycorrhizal fungi (EmF), of which Russulaceae is a key lineage, has greatly increased due to the recognition of the importance of EmF …
Ecological And Evolutionary Dynamics Of Plant-Soil Feedbacks: Influences On Evolution And Range Dynamics, Michael E. Van Nuland
Ecological And Evolutionary Dynamics Of Plant-Soil Feedbacks: Influences On Evolution And Range Dynamics, Michael E. Van Nuland
Doctoral Dissertations
Plants interact with, modify, and are affected by their soil environments. Though plant-soil interactions are well known to be important and active regulators of ecosystem function and community structure, much less is known about how these interactions affect plant evolution. The primary goal of my dissertation was to examine plant-soil interactions under a range of ecological and evolutionary contexts to better understand patterns of biodiversity, ecosystem function, and whole system responses to environmental change. Taking such an eco-evolutionary perspective allows for a holistic understanding of the causes and consequences of complex abiotic and biotic interactions that link ecosystem ecology and …
Molecular Phylogenetic Studies Of The Genera Of Tribe Polygonateae (Asparagaceae: Nolinoideae): Disporopsis, Heteropolygonatum, And Polygonatum., Aaron Jennings Floden
Molecular Phylogenetic Studies Of The Genera Of Tribe Polygonateae (Asparagaceae: Nolinoideae): Disporopsis, Heteropolygonatum, And Polygonatum., Aaron Jennings Floden
Doctoral Dissertations
The Polygonateae (Asparagaceae) are a subtribe of the Nolinoideae that is redefined here to include three genera which are investigated here: Disporopsis; Heteropolygonatum, and Polygonatum. This group of genera, characterized by their axillary-flowered habit, are closely related but differ greatly in their morphology, cytology, and diversity. A molecular phylogeny is presented to show their relationships to one another and to closely related outgroups based on data from whole chloroplast genomes with low taxonomic sampling. The results show that the genera of the Polygonateae are each monophyletic, and also show that a fourth genus, Maianthemum, that was …
Trait Evolution In Spiders: Perspectives On The Evolution Of Behavioral Syndromes And Web Structures, Jennifer Marie Bosco
Trait Evolution In Spiders: Perspectives On The Evolution Of Behavioral Syndromes And Web Structures, Jennifer Marie Bosco
Doctoral Dissertations
Organisms have evolved complex behavioral, morphological and physiological traits in response to various selection pressures. These phenotypes are usually composed of many traits that may or may not be genetically or phenotypically correlated. Correlations of both types can lead to evolutionary trade-offs, which may be broken over long evolutionary time periods through such mechanisms as the decoupling of genetic linkages and the development of phenotypic plasticity. Behavioral traits associated with temperament provide an excellent system in which to evaluate underlying mechanisms of the establishment and decoupling of genetic linkages. Other traits, such as the type of web that a spider …
Using Phylogenetic Comparative Methods To Understand Diversification And Geographic Range Evolution, Kathryn Aurora Massana
Using Phylogenetic Comparative Methods To Understand Diversification And Geographic Range Evolution, Kathryn Aurora Massana
Doctoral Dissertations
Two key processes that have been modeled in a phylogenetic comparative framework are diversification and historical biogeography. Many questions arise on what process have shaped the abundance (or lack) of species we see today and what influences their survival and interconnectedness with other species. Many methods have been developed to answer these questions. Over the past several decades there has been a rise in parametric modeling and development of more adequate frameworks to answer biological questions of interest. However, many models still lack the incorporation of ecological, mainly biotic factors, which influence the evolution and ecology of species, while accounting …