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University of Nebraska - Lincoln
School of Biological Sciences: Dissertations, Theses, and Student Research
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Articles 1 - 6 of 6
Full-Text Articles in Population Biology
Prey Selection By Birds Of Prey, Anisha Pokharel
Prey Selection By Birds Of Prey, Anisha Pokharel
School of Biological Sciences: Dissertations, Theses, and Student Research
Prey selection is key to determine predator prey interaction and understanding the complexity of food web structure. In this thesis, we used two different approaches to understanding prey selection by North American birds of prey. Using a conventional method, in Chapter 1 we compared pellet analysis and trapping data to assess patterns of prey selection of barn owls in western Nebraska. Microtus spp. comprised 55.8% of the prey items in the barn owl’s diet. The proportion of several prey types in the diet were significantly different from the expected proportion based on trapping. This pattern may indicate barn owls actively …
The Joint Effect Of Phenotypic Variation And Temperature On Predator-Prey Interactions, Jean P. Gibert
The Joint Effect Of Phenotypic Variation And Temperature On Predator-Prey Interactions, Jean P. Gibert
School of Biological Sciences: Dissertations, Theses, and Student Research
Understanding the factors underpinning to food web structure and stability is a long-standing issue in ecology. This is particularly important in a context of global climate change, where rising environmental temperatures may impact the way species interact, potentially leading to changes in food web structure and to secondary extinctions resulting from cascading effects. In order to understand and predict these changes, we need to hone our comprehension on the way predators and their prey interact. Recent studies suggest that, in order to do so, we need to focus on the traits controlling those interactions, such as body size. Mean body …
Population And Morphological Changes In American Kestrels Through Space And Time, Teresa E. Ely
Population And Morphological Changes In American Kestrels Through Space And Time, Teresa E. Ely
School of Biological Sciences: Dissertations, Theses, and Student Research
A once common raptor, the American kestrel (Falco sparverius) has experienced population declines in the last two decades throughout North America. Many hypotheses exist about the decline, including mortality from West Nile virus, rodenticide poisoning, climate change, an increase in predators, and core habitat loss or degradation, which could influence food availability. Food availability is key to raptor survival and reproduction, and changes in food availability throughout the year can have lifelong effects on size and body condition. Here we examine how morphology, specifically mass and wing chord, has changed at seven migration sites throughout North America as …
Multilocus And Parametric Analyses Of The Evolutionary History Of The Amazonian Peacock Cichlids, The Genus Cichla (Teleostei: Cichlidae), Stuart Willis
School of Biological Sciences: Dissertations, Theses, and Student Research
Accurate knowledge of species boundaries and species phylogeny are fundamental to testing hypotheses of recent evolutionary processes, but the estimation of these partitions is challenging due both to inherent confusion about what is being estimated as well as the data available to estimate them. Using multilocus data from mtDNA, microsatellites, and nuclear locus sequences of over 1100 individuals, we delimited eight separately evolving species of Cichla rather than the 15 described. Among species we found evidence of rare but widespread introgressive hybridization, while within these species we observed evidence of long-term gene exchange and constrained evolutionary trajectories. In most cases …
Ecological Effects Of Virus-Resistant Transgenic Squash, Holly R. Prendeville
Ecological Effects Of Virus-Resistant Transgenic Squash, Holly R. Prendeville
School of Biological Sciences: Dissertations, Theses, and Student Research
Two ecological risks associated with the use of transgenic crops include the effects of transgene products on non-target organisms and the effects of a transgene after it moves from crops into a wild plant population. In work presented here, we specifically investigate the ecological risks of virus-resistant transgenic squash. We observed pollinator behavior to determine if pollinators are affected by nontarget effects of the virus-resistant transgene. We found that pollinator behavior did differ between conventional and virus-resistant transgenic squash due to pleiotropic effects of the transgene. This difference in pollinator behavior can affect plant mating patterns, thereby affecting crop-wild hybridization …
Time, Temperature And Species Interactions In A Duckweed-Herbivore Mesocosm, Ian Waterman
Time, Temperature And Species Interactions In A Duckweed-Herbivore Mesocosm, Ian Waterman
School of Biological Sciences: Dissertations, Theses, and Student Research
Species interactions within a community are impacted by a variety of abiotic factors. Temperature is known to alter population dynamics such that direct and indirect interactions between populations within a community are affected. Here I investigate the effect of temperature change on species interactions within a duckweed-herbivore mesocosm. Multiple communities were constructed, from a single population of duckweed, to two populations of duckweed consumed by aphids. In the one-predator two-prey web we predicted mutually positive indirect effects between duckweed populations during the first generation of growth. As aphid populations respond numerically to more abundant prey, mutually negative and asymmetric indirect …