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Dissertations / Theses on the topic 'Ecology and Evolutionary Biology'

Author: Grafiati

Published: 4 June 2021

Last updated: 25 July 2025

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1

Gregg, Tamara. "Predator-prey ecological and evolutionary dynamics: The cost of a counter-defense drives the evolutionary outcome." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103650.

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In this thesis I explore the co-evolutionary dynamics of defences and counter-defences in a predator-prey interaction. I hypothesize that the cost of defences and counter-defences result in the cycling of these traits under all circumstances: directional selection alternate between increasing and decreasing trait values (defense of the prey and counter-defense of the predator). Using Taricha granulosa and Thamnophis sirtalis as an example of a predator-dangerous prey system, I modeled the ecological and evolutionary dynamics of predator-prey interactions and analyzed the results from equatio

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2

Osmond, Matthew. "Eco-evolutionary rescue: an adaptive dynamic analysis." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107917.

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Populations exposed to changing environments often decline in abundance and may therefore find themselves at risk of extinction. Safe abundances can be regained, and persistence secured, when populations can adapt fast enough. Here I ask how population and environmental factors determine a population's ability to persist in changing environments by adapting genetically. In Chapter 2 I investigate the response to a gradual, directional change in the environment and in Chapter 3 I investigate the response to a sudden, sustained shift. Chapter 3 also discusses the effects of interspecific competi

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3

Pillay, Pradeep. "The ecological and evolutionary assembly of trophic metacommunities." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96666.

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Despite the important role spatial processes play in natural communities, far too little theoretical work has been devoted to exploring how complex food web communities may be assembled in space, and how the spatial structure of trophic interactions may provide a stabilizing mechanism for complex food web networks. In this thesis I develop a food web metacommunity model based on a classic Levins-type patch-dynamic model which views trophic interactions between species as occurring in a spatially subdivided habitat. I then use this model to explore both simple and complex trophic networks in an

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4

Kylafis, Grigorios. "Niche construction, facilitation and their ecological and evolutionary consequences." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97086.

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Organisms modify their environment through their activities and by doing so, they modify evolutionary pressures acting on them, as well as the ecological conditions under which they grow and reproduce. Niche construction, as defined by Odling-Smee et al. (2003), is a concept that captures the reciprocal organism-environment interaction from an evolutionary perspective. However, niche construction in the sense of biotically-driven improvement of the ecological environment has been poorly explored to date. I derive a consumer-resource model to investigate the consequences of niche construction f

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Low-Décarie, Etienne. "Ecological and evolutionary response of phytoplankton to rising CO2." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121204.

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Atmospheric CO2 concentration has risen to a landmark high of 400 ppm, a level not seen on earth for the past million years, and is expected to continue to increase over the course of this century. Besides its indirect effect on climate, this change will directly affect all photosynthetic organisms, including phytoplankton, through an increased availability of carbon. Through laboratory and field experiments, I investigated the ecological and evolutionary response of phytoplankton communities to rising atmospheric CO2. The rise in atmospheric CO2 is occurring at the same time as increases i

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6

Burgos, Luis Patricio. "The Thermal Ecology of Sceloporus occidentalis." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/2062.

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With temperatures rising globally, assessing the possible impacts of the changing climate becomes more and more urgent. Ectotherms are excellent indicators of potential climatic ramifications on biodiversity because of their heavy reliance on the environment for their thermoregulation. Studies have historically looked at thermal tolerance values to establish predictive models for population and species extinctions. In chapter 1, we looked at recent studies that suggest that thermal tolerance may be a plastic trait and test the effects empirically. Most studies are based on captive lizards accl

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7

Abbot, Douglas Kilpatrick. "Evolutionary genetics of gall-forming aphids: Population and behavioral processes." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/279854.

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I investigated patterns of genetic variation in the North American gall-forming aphid, Pemphigus obesinymphae. In Chapters 2a and 2b, I developed and then implemented clone-specific molecular markers to investigate clonal mixing in P. obesinymphae . During its gall-forming phase, P. obesinymphae clones produce aggressive larval "soldiers", which altruistically defend their colonies from natural enemies. I showed that movement occurs between galls, indicating that P. obesinymphae colonies are not pure clones. I also showed that intruders behave selfishly, by not defending unrelated clones, and

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8

Machovina, Brian. "The Role of Agriculture and Food Consumption in Tropical Conservation." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/1841.

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A growing human population, shifting human dietary habits, and climate change are negatively affecting global ecosystems on a massive scale. Expanding agricultural areas to feed a growing population drives extensive habitat loss, and climate change compounds stresses on both food security and ecosystems. Understanding the negative effects of human diet and climate change on agricultural and natural ecosystems provides a context within which potential technological and behavioral solutions can be proposed to help maximize conservation. The purpose of this research was to (1) examine the potenti

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9

Ramirez, Aaron Robert. "Comparative Ecophysiology and Evolutionary Biology of Island and Mainland Chaparral Communities." Thesis, University of California, Berkeley, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3720783.

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<p> The unique nature of island ecosystems have fascinated generations of naturalists, ecologists, and evolutionary biologists. Studying island systems led to the development of keystone biological theories including: Darwin and Wallace's theories of natural selection, Carlquist's insights into the biology of adaptive radiations, MacArthur and Wilson's theory of island biogeography, and many others. Utilizing islands as natural laboratories allows us to discover the underlying fabric of ecology and evolutionary biology. This dissertation represents my attempt to contribute to this long and sto

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10

Inglis, Robert Fredrik. "The evolutionary ecology of spiteful bacteriocin production." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:524eaef3-0336-4127-9cd1-60d84a00f2e3.

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Understanding the conditions that favour the evolution and maintenance of spiteful bacteriocin production combines two important questions from the fields of social evolution and microbiology. Spiteful behaviours, though, initially thought to be rare represent an important class of interactions between bacteria through the production of bacteriocins. Bacteriocins can be considered spiteful as they are costly to produce (in many cases requiring lysis) and are costly to sensitive bacteria (i.e. they are lethal). However, much about the ecology of spiteful behaviours and bacteriocin production re

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11

Schaffner, Linda C. "Ecology of the benthos of the lower Chesapeake Bay (Maryland)." W&M ScholarWorks, 1987. https://scholarworks.wm.edu/etd/1539616841.

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The spatially complex lower Chesapeake Bay estuary is characterized by a variety of bottom types and hydrodynamic regimes. to account for this physically-induced variability a benthic habitat delineation scheme was developed based on existing knowledge of physical and geological characteristics. Within the context of this scheme a series of studies were conducted to identify biotic response to and interactions with the physical, chemical and geological gradients that characterize the lower Chesapeake Bay. These studies characterized organism distribution and abundance patterns within the lower

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Schoenberger, Shirley Ann 1943. "High-temperature adaptation of three Sonoran Desert Bacillus species: Ecological and evolutionary prospects." Thesis, The University of Arizona, 1996. http://hdl.handle.net/10150/278546.

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Growth at high temperature of wild isolates of three species of Bacillus was analyzed to assess potential responses to global warming. Experimental populations were grown at temperatures from 32° to 60° C. The higher temperatures include ones near and above maxima previously reported for laboratory strains. Summer soil temperatures, three centimeters below the ground surface, were recorded at the same site from which the wild isolates came, show that temperatures in the Sonoran Desert often reach 50° to 60° C. The growth data show that the desert isolates of B. subtilis and B. licheniformis ha

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Myers, Patrick J. "Spatial Ecology and Captive Behavior of Rehabilitated Black Bears in Utah." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/5232.

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Animal movements and space use are fundamental components of life and play integral roles in organismal fitness, population dynamics, and the ecology and evolution of species. The heterogeneous distribution of resources and the movement required to access them, results in ecology being a fundamentally spatial concept. Thus, elucidating animal-habitat relationships is a central focus of wildlife ecology and conservation. I utilized GPS technology, resource selection functions, and generalized linear mixed models, to investigate the immediate post-release movements, denning chronology, release-s

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Byles, Richard Allan. "Behavior and ecology of sea turtles from Chesapeake Bay, Virginia." W&M ScholarWorks, 1988. https://scholarworks.wm.edu/etd/1539616593.

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Immature foraging sea turtles occupy Chesapeake Bay, Virginia annually from May through November. Telemetry was used to monitor the movements and behavior of loggerhead, Caretta caretta, and Kemp's ridley, Lepidochelys kempi, turtles during 1981-1985. Both species utilized the estuary for summer foraging, but exhibited habitat-preference and behavioral differences that amounted to resource partitioning between the species. Loggerheads oriented towards major river outflows and tended to move along channel sides with the tidal flow while ridleys occupied shallower foraging areas and did not rang

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Buschbeck, Elke Karin Ursula 1967. "Conservation of "magnocellular" neurons of the dipteran optomotor pathway: Evolutionary and functional implications." Thesis, The University of Arizona, 1994. http://hdl.handle.net/10150/278434.

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In Diptera, small-field retinotopic neurons supply achromatic motion sensitive neurons in the lobula plate, a region thought to control stabilization of yaw, pitch, and roll during flight. If different body shapes, and the flight performance associated with them, place specific demands on the design of control pathways, it might be expected that flies with long bodies and high aerodynamic pitch stability would show specific differences in the organization of such magnocellular achromatic networks. Striking differences emerge in the comparison of 9 species. Tipulids and culicids possess small n

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Downing, Jason L. "Consequences of Anthropogenic and Global Change on Orchids: An Emphasis on Biotic Interactions." FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2448.

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Evidence suggests that human-driven changes to the earth are having clear and profound effects on many species, as well as the species with which they associate. Disruptions in the interactions between species can change the community structure, in turn changing the dynamics of entire ecosystems. The following dissertation examines how the impacts of climate change related events and invasive species may influence biotic interactions and impact orchid populations and range distributions. Here I quantify how orchid pollinators and mycorrhiza vary between species with different life histories, a

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Buchheister, Andre. "Structure, Drivers, and Trophic Interactions of the Demersal Fish Community in Chesapeake Bay." W&M ScholarWorks, 2014. https://scholarworks.wm.edu/etd/1539616586.

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Management of fisheries resources is increasingly broadening its scope from single-species approaches to more holistic, ecosystem-based approaches that account for interactions of fish with a variety of ecological factors, such as predators, prey, and habitat. This ecosystem based fisheries management (EBFM) approach requires thorough biological and ecological understanding of systems pertaining to community structure, habitat suitability, and food web interactions. to strengthen the ecological underpinnings of EBFM efforts in Chesapeake Bay, the largest estuary in the USA, I conducted synopti

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Peterson, Chris C. "Conservation Implications Of Winter-Feeding Policies For Mule Deer In Utah." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/108.

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Policies regulating wildlife winter-feeding programs may have long-term impacts on conservation and future management of both target and non-target species. In 2000, the Utah Wildlife Board, upon reviewing input from a series of public regional meetings, adopted a Utah Big Game Winter-Feeding Policy. The Utah Division of Wildlife Resources used this policy to regulate winter-feeding programs for mule deer in northern Utah, 2001-2005. I monitored the program effects on mule deer biology, activity and migration, and winter browse utilization and productivity. While feed rations generally compens

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Cavalcanti, Sandra Maria Cintra. "Predator-Prey Relationships and Spatial Ecology of Jaguars in the Southern Pantanal, Brazil: Implications for Conservation and Management." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/112.

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The Pantanal wetland of Brazil is an important area for the conservation of jaguars (Panthera onca) and a stronghold for the species. Although our knowledge of jaguar ecology has increased since the first field studies in the mid 1980’s, a detailed study of this cryptic species remains challenging. In the following chapters, we investigated the ecology of jaguars in the southern Pantanal of Brazil. In Chapter II, we examined the foraging ecology of jaguars, documenting predation rates, patterns, and species killed. We found individual jaguars differed in the selection of their prey. There were

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Wells, Elizabeth Hamilton. "Evolutionary novelty and naivete in invertebrate predator-prey interactions in a benthic marine community." Thesis, University of California, Davis, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3565574.

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<p> In the first chapter of this dissertation, I explore the role of shared evolutionary history in determining predation preferences of a suite of three generalist muricid whelks preying on oysters and mussels. Various theories such as the enemy release and novel weapons hypotheses predict how evolutionary novelty will affect predator-prey interactions, but it is not clear how applicable these theories are to interactions between generalist predators and familiar prey types. In addition to determining whether the one native and two invasive whelks preferred to consume evolutionarily familiar

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21

Goldman, Kenneth J. "Aspects of age, growth, demographics and thermal biology of two lamniform shark species." W&M ScholarWorks, 2002. https://scholarworks.wm.edu/etd/1539616670.

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Age and growth rates for salmon sharks (Lamna ditropis) in the eastern North Pacific (ENP) were estimated from seasonally formed bands in the vertebrae, and compared to previously published life history parameters for this species from the western North Pacific (WNP). Results of this study show that salmon sharks in the ENP achieve their maximum length at a faster rate, reach sexual maturity at an earlier age and achieve a greater weight-at-length than those in the WNP. Additionally, this dissertation shows that adult salmon sharks maintain a specific body temperature independent of changes in

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22

Lowerre-Barbieri, Susan. "Life history and fisheries ecology of weakfish, Cynoscion regalis, in the Chesapeake Bay region." W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539616753.

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Otoliths, scales, dorsal spines, and pectoral fin rays were compared to determine the best hardpart for ageing weakfish, Cynoscion regalis. Sectioned otoliths showed the clearest marks and were validated by the marginal increment method for ages 1-5. Traditionally-used scales were found to be less-precise and to underage older fish. Most weakfish from the Chesapeake Bay region were 200-600 mm TL and ages 1-4. Weakfish were not fully-recruited to commercial foodfish grades until age 2. Maximum observed age was 17 from a Delaware Bay fish collected in 1985. Current maximum observed ages were age

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23

Lachapelle, Josianne. "The effect of sex and diversity on evolutionary rescue in experimental populations of Chlamydomonas reinhardtii." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107908.

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The environmental change experienced by many contemporary populations of living organisms poses a serious risk to their survival. From the theory of evolutionary rescue we predict that the combination of diversity and sex should increase the probability of survival by increasing genetic variation and consequently increasing the probability of generating a type that can tolerate the stressful environment. I tested this prediction by comparing six kinds of experimental populations of Chlamydomonas reinhardtii that differ in the initial amount of genetic diversity and in sexuality. The lines were

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Wu, Gi-Mick. "On handling costs and host choice in aphid-parasitoids: from individual behaviour to evolutionary patterns." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103627.

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Foraging animals incur handling costs when capturing, subduing, or killing their resources. Handling costs are hypothesized to influence the dietary choices of animals and influence the structure of ecological communities. It is not clear, however, whether trophic interactions found in communities correspond to individual decisions. This thesis investigated the determinants of handling costs and their consequences for host choice by aphid parasitoids (Hymenoptera, Braconidae, Aphidiinae) at the level of individuals and communities. Laboratory experiments using the parasitoid Aphidius colemani

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Horodysky, Andrij Z. "Comparative sensory and energetic ecology of sciaenid fishes and their competitors in Chesapeake Bay, VA." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616699.

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Coastal fishes of the western North Atlantic, such as sciaenids and their competitors, support substantial commercial and recreational fisheries in waters that may vary widely in temperature, salinity, light intensity and spectral distrubution, and dissolved oxygen levels, yet their ecophysiological abilities to cope with such variability have received little attention. I therefore applied multidisciplinary comparative techniques to investigate aspects of the sensory and energetic ecophysiology of several sciaenid fishes and non-sciaenid competitors common in the western North Atlantic. Audito

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Jarvis, Jessie C. "Function of seed-bank ecology in mid-Atlantic semi-annual and perennial Zostera marina beds." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539616708.

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The effects of water quality and sediment composition on mid-Atlantic semi-annual and perennial Zostera marina reproductive success, seed-bank viability, and seed germination were elucidated using laboratory and in situ experiments, quantitative field observations, and ecological model simulations. The sediment seed-bank was found to play a large role in the recovery of perennial Z. marina beds in the Chesapeake Bay and in the yearly re-establishment of beds in North Carolina which were determined to have a semi-annual life history. However, the resiliency provided by sediment seed-bank for bo

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Ross-Gillespie, Adin. "Model socialite, problem pathogen : the evolution and ecology of cooperation in the bacterium Pseudomonas aeruginosa." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/3134.

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In recent decades we have learned that cooperation is an important and pervasive feature of microbial life. This revelation raises exciting possibilities. On the one hand, we can now augment our understanding of how social phenomena evolve by using microbial model systems to test our theories. On the other hand, we can use concepts from social evolution to gain insight into the biology of the microbes we hope to control or kill. In this thesis I explore both possibilities. First, I consider the theoretical problem of how and when microbial cooperation might be subject to frequency- and density

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McNutt, David William. "Evolutionary constraints on plasticity in the anti-herbivore defenses of Solanum carolinense." Thesis, The Florida State University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3612462.

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<p> Many organisms live in temporally or spatially heterogeneous environments. One adaptive response to environmental heterogeneity is phenotypic plasticity, or the ability of an organism to change its phenotype in response to environmental variation. Plasticity is particularly important for plants, which cannot easily escape environmental stresses (e.g., competition, herbivory, or drought), and therefore is common in many morphological and physiological traits that allow plants to cope with stresses. Despite numerous examples of the adaptive value of plasticity in plant traits, the reaction n

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THOMAS, RICHARD HENSLEE. "EFFECTS OF SPATIAL DISTRIBUTIONS OF INDIVIDUALS ON MODELS OF ISOLATION-BY-DISTANCE." Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188017.

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Effective population size is one of the fundamental parameters in many population genetic models. It provides a common currency to compare populations by reference to an analytically tractable ideally behaving population. Different values of this parameter can have very significant effects on rates and modes of evolution. Sewall Wright's shifting balance theory stresses the importance of drift interacting with selection and dispersal in the process of evolution. For this process to work requires effective deme sizes of no more than a few hundred. Errors of only one order of magnitude can serio

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Sloat, Lindsey Leigh. "Causes and Consequences of Plant Responses to Environmental Change over Physiological, Ecological, and Evolutionary Time." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/594929.

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Assessing how environmental change affects plants is increasingly important as terrestrial ecologists attempt to predict future patterns from current processes. However, this challenge is complicated because plant communities can respond to environmental variation at different, but overlapping scales. Additionally, both patterns and the processes that drive them are sensitive to the methods that scientists use to study them. Consequently, a variety of experimental and theoretical approaches are necessary to improve our understanding of how organisms, communities, and ecosystems will respond to

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Ruboyianes, Ryan. "Foamy-like Endogenous Retroviruses Are Abundant and Extensive In Teleosts." Thesis, The University of Arizona, 2015. http://hdl.handle.net/10150/594955.

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Spumaretrovirus, among retrovirus clades, has an extensive accumulation of evidence for an ancient origin. Recent discoveries indicate that the Spumaretrovirus ancestor could have been the first retrovirus to appear during the evolution of vertebrates. If they indeed appeared in ancient marine environments hundreds of millions of years ago, we should expect significant undiscovered diversity of foamy-like endogenous retroviruses in fish genomes. I report the discovery of these elements in 23 novel teleost hosts. These viruses have very large genomes compared to all other retroviruses, possess

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Longmire, Katherine Sara. "Effects Of Acidification And Salinity On Callinectes Sapidus, Mercenaria Mercenaria, And Their Interactions." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1616444437.

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Ocean acidification (OA) coupled with other stressors, will be detrimental at the species and ecosystem levels. Decreased carbonate ion concentrations negatively impact calcifying species, yet the combined effects of OA and other stressors are less well known, and many studies disregard species interactions. Multi-species studies involving OA and other stressors are crucial to comprehend the full threat of OA. Understanding how OA interacts with other stressors to affect species responses is necessary for future management of exploited species in an altered ecosystem. The objectives of my stud

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Colden, Allison M. "Biophysical Control of Oyster Reef Performance in Chesapeake Bay." W&M ScholarWorks, 2014. https://scholarworks.wm.edu/etd/1593092090.

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Mitchell, Molly. "Impacts of Sea Level Rise on Tidal Wetland Extent and Distribution." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1530192833.

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Tidal marshes are a major ecological resource in Virginia and a driver of many estuarine functions. Therefore, the long term sustainability of tidal marsh ecosystems is a question of great interest in the research community. Sea level is rising at an unusually high rate in the Chesapeake Bay relative to most of the Atlantic coastline, putting Bay marshes at high risk from drowning and erosion. Sea level rise-driven salinity changes communities and alters ecosystem services. Understanding the patterns of change and the importance of different drivers of change is critical to tidal marsh sustain

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Parker, John Daniel. "Does Plant Diversity Control Animal Diversity?: An Experimental Approach." W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539617738.

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Hawkins, Carly Elizabeth. "Effects of Anthropogenic Noise on Songbird Social Networks." W&M ScholarWorks, 2018. https://scholarworks.wm.edu/etd/1550153791.

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Anthropogenic noise, which is increasing globally, affects birds from gene expression up through alteration of community composition. as urbanization pushes further into undisturbed habitat, noise often disperses birds away from the point source. The impacts of this dispersal on surrounding quieter areas is not well understood. Therefore, in the first chapter, we sought to understand how noise-related dispersal affected the sociality of groups of songbirds as they moved away from the source of noise. as the displaced birds would likely be forced to occupy a smaller area that may already have r

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DAVIS, RACHEL Leigh. "Effects Of Dietary Methylmercury Exposure On Tissue-Specific Telomere Dynamics In The Zebra Finch (Taeniopygia Guttata)." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091499.

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The organic, methylated form of mercury (Hg), methylmercury (MeHg), is a highly toxic global pollutant that affects humans, wildlife, and ecosystem health. While exposure to high dosages of MeHg is often fatal, much less is known about the physiological effects of exposure to lower, sub-lethal dosages. Further understanding of how MeHg exposure alters organ performance at a cellular level is critical to understanding the health effects on both humans and wildlife impacted by environmental contamination. To assess the impact of MeHg on eukaryotic organisms, we tested how lifetime, dietary expos

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Mason, Sam. "Within-Flight-Period Dynamics Driven By Phenology And Transect Quality, Not Patch Size Or Isolation, In A Specialist Butterfly, Panoquina Panoquin." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091614.

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As sea levels rise, coastal salt marshes, and the organisms for which they provision, face existential threats. A first step in understanding how projected marsh loss and reconfiguration may impact obligate species is to define their contemporary distribution and temporal shifts in structure using dynamic occupancy models. While occupancy models have commonly been applied to multi-annual butterfly studies, few have investigated population dynamics within a single-season. Here, we used Bayesian dynamic use models to define within-flight-period trends in adult salt-marsh skipper (Panoquina panoq

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Braff, Pamela. "Evaluating The Impacts Of Land Use And Climate Change On The Hydrology Of Headwater Wetlands In The Coastal Plain Of Virginia." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091561.

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Located at the interface between uplands and surface water networks, headwater wetlands act as a natural filter to improve downstream water quality and play a critical role in maintaining the ecological integrity of downstream aquatic ecosystems. Vulnerable to development pressure, as well as indirect impacts from land use and climate change, the loss and alteration of headwater wetlands has been linked to the loss of biodiversity and regional water quality declines worldwide. The overall goal of this dissertation is to address some of the challenges associated with the management and conserva

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Galvin, Robert Michael. "A Comparison Of Shorebird Habitat Use Between Living Shorelines And Natural Fringing Marshes." W&M ScholarWorks, 2020. https://scholarworks.wm.edu/etd/1593091811.

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We examined the use of fringing marshes by herons and shorebirds in the southern portion of Chesapeake Bay. From 13 pairs of natural fringing marshes and nearby, constructed living shoreline marshes, we completed analysis of videos recorded at discrete, 30-minute intervals (dawn, dusk, high tide, low tide) throughout the 2018 and 2019 field seasons (May through August). A total of 684 hours of recording yielded 91 individual observations of birds comprising six species. Spotted Sandpipers (Actitis macularius) were observed most frequently (25), but only at living shoreline marshes. Likewise, 1

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Bartholomew, Aaron. "New dimensionless indices of structural habitat complexity." W&M ScholarWorks, 2001. https://scholarworks.wm.edu/etd/1539616561.

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Ecologists have long known that complex habitats often provide prey with refugia from predation in a wide variety of habitat types and for a wide variety of prey species. Despite the recognized importance of structural habitat complexity, ecologists have measured complexity in many different ways. I propose four new indices of structural habitat complexity that are dimensionless, that can be applied across various habitat types and scales, and that directly measure how structural complexity interferes with a predator's foraging ability. These indices are: (1) Ct/At, the total area of cover wit

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Helm, Bryan Robert. "An Ontogenetic Perspective on the Timing of Maturation in Insects with Special Consideration of Physical and Resource Thresholds." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/301531.

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All animals progress through a series of functionally discrete life stages from fertilization through adulthood and often into senescence. Reproduction in the adult stage can only occur after maturation--the final life history transition during ontogeny--from juvenile to adult. Despite a robust literature that predicts the optimal body size and development time at which this transition should occur, the ontogenetic factors that are responsible for determining metamorphosis and the manner in which they are translated into the hormonal mechanisms regulating maturation remain unresolved in most

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Shelton, Deborah. "The Shifting Role of Cell Division During an Evolutionary Transition to Multicellular-Level Individuality." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/311564.

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During the transitions from unicellularity to multicellularity, cells transitioned from functioning as wholes to functioning as parts of wholes. In the colonial freshwater green flagellates known as volvocine algae, living "intermediate form" species give ample evidence concerning how cells gradually lost autonomy and began functioning as dedicated parts. This dissertation concerns how and why the role of cell division changed in unicellular to colonial volvocine algae. We review a recent book on levels of selection and apply a proposed three-stage transition to the example of volvocine algae.

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Blonder, Benjamin. "Leaf Venation Networks Link Climate to Plant Form and Function." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/316935.

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Within each leaf is an intricate network of veins. The geometry of this network shows large variation across species and environments, paralleling variation in species' functioning and geographic distributions. Here I develop theory that links leaf venation networks to 1) the worldwide leaf economics spectrum, enabling better understandings of the resource tradeoffs that are central to the terrestrial carbon and water cycles, and 2) atmospheric temperature and carbon dioxide concentrations, enabling better use of leaf fossils for paleoclimate reconstruction. I successfully test these theories

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Yuan, Chi. "Perennial Plant Models to Study Species Coexistence in a Variable Environment." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338881.

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Living organisms face a changing physical environment. A major challenge in ecology is understanding the ecological and evolutionary role that this changing physical environment has in shaping a community. One fundamental question is how environmental variation affects species coexistence. Modern understanding of environmental variation emphasized the hypothesis that possible adaptations to a fluctuating environment allow species to use different environments in different ways. Species can partition temporally their use of resources. Persistent stages in the life cycle such as prolonged longev

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McCarthy, Megan Campbell. "Plant Biomass Allocation: Understanding the Variability within Size Constraints." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194007.

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The majority of studies on plant biomass partitioning have focused on the effects of environment. Optimal Partitioning Theory (OPT) suggests that plants should allocate biomass to the organ that acquires the most limiting resource. Though, it has recently been disputed as to how much of this variation is due to variation in size and not environment. Additionally, while a few studies have examined differences between growth forms, the effects of evolutionary history have been largely ignored. Leaf morphology and physiology may also contribute to patterns of biomass partitioning.The role of p

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Swenson, Nathan Garrick. "The Influence of Phylogenetic and Functional Similarity on Species Coexistence Through Space and Time." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194918.

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The problem of species diversity and co-existence in hyper-diverse communities remains. Traditionally ecologists have approached this problem from examining patterns of co-occurrence, interaction matrices and abundance distributions. This work, while productive, generally has rarely explored the role of shared ancestry and species-specific quantitative function in promoting species diversity and co-existence. This has been a critical oversight as simply analyzing the list of Latin binomials in an assemblage ignores the relatedness between taxa as well as the diversity in organismal form and f

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Wood, Elizabeth T. "Genetic Variation in African Populations: A Multi-Locus Approach to Understanding Selection and Demography in Humans." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/195188.

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Mutation, recombination, selection, and demographic processes (such as gene flow and genetic drift) have shaped genetic variation, but the relative impact of these evolutionary forces remains poorly understood. This problem motivates this study which examines three regions of the genome -beta-globin, the Y-chromosome, and mtDNA- in a two part approach to assess the relative impact of evolutionary forces on human genetic variation in Africa. The first approach characterizes levels of nucleotide variability and linkage disequilibrium across thebeta-globin gene and recombinational hotspot in a

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Eilts, J. Alexander. "The Physiology of Exploitation Competition." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/195710.

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Water is a critical resource for which plants compete in many terrestrial communities. In arid communities where water most limits plant growth, rainfall events occur in discrete, pulsed events. These pulses of water create highly variable soil moisture availabilities. Plant species respond differently to variation in soil water availabilities throughout a season and between years. How species vary in their responses to a range of water availabilities is thought to influence community and ecosystem properties. Many previously proposed hypotheses are not suitable to explain rapidly fluctua

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Humphreys, Abbey. "Predicting the Impact of Sea Level Rise on the Distribution of Phragmites Australis and Spartina Alterniflora and Changes in Community Compositions in Tidal Freshwater Marshes of James City County, Va." W&M ScholarWorks, 2017. https://scholarworks.wm.edu/etd/1516639677.

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With ongoing sea level rise (SLR), tidal freshwater marshes (TFMs) eventually will be flooded with more brackish water. The impact of more water and salt on the plant community of TFMs, however, is unknown. With SLR, both the invasive reed Phragmites australis and the native salt marsh grass Spartina alterniflora could become dominant species in TFMs. I am looking at determining how increases in salinity and inundation caused by sea level rise will impact the relative distribution of Phragmites and Spartina in tidal freshwater marshes in Southeastern Virginia. Using GIS, I summarized past ex

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