Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 31 for “"Divergent selection"”.
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Divergent Selection for Water Conversion Ratio in Broiler Populations
… low flow water monitoring system, it was used to divergently select for water efficiency in broilers. This was done too not only to help determine heritability of water efficiency but to assess the direct response to selection and impact on correlated traits. From a modern random bred population, …
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Local adaptation to parasites and selection on major histocompatibility genes in ecologically divergent populations of three-spine stickleback (Gasterosteus aculeatus)
… is little direct empirical support for spatially divergent selection driving local adaptation on MHC loci in the wild. In chapter two I tested for the action of parasite mediated balancing and divergent selection on on MHC loci using naturally infected stickleback in three replicate lake-stream …
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A Geographic Mosaic of Speciation in Eurosta solidaginis
Ecological speciation occurs when divergent selection in different habitats creates strong selection for reproductive isolation which counteracts the homogenizing effects of gene flow between populations using those different habitats. Multiple divergent selection pressures can affect isolation and …
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Selection for Body Weight in Chickens: Resource Allocations and Scaling
… were correlated responses to 54-generations of divergent selection for 8-week body weight (BW) and of BW at other ages and reproductive traits. Evaluated first was the influence of scaling on phenotypic responses to selection, phenotypic correlations of means and standard deviations, and …
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Diet, adaptation and the evolution of assortative mating in Ceratitis capitata
Abstract The action of natural selection in establishing barriers to gene flow between populations, or reproductive isolation, is increasingly understood to be a primary driver of speciation and thus biodiversity. ‘Ecological speciation’ is now supported by evidence from numerous studies in a range …
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Correlated physiological responses in a bidirectional selection experiment for body weight in chickens
… in two lines of chickens that had undergone divergent selection for body weight at eight weeks of age. The latter three traits were studied in two light environments, continuous illumination and a ratio of 8 hours light to 16 hours darkness. The dissertation involved two experiments and …
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Regulation of floury2-mRFP expression in response to long term selection for grain protein concentration in maize
The Illinois Long-term Selection Experiment is the longest running continuous genetics experiment in higher plants in the world. Seven hundred and twenty-one cycles of divergent selection for grain protein and oil concentration have produced populations with the known phenotypic extremes for this …
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Noise and signal transmission properties as agents of selection in the vibrational communication environment
… in plant transmission properties can promote divergent selection on vibrational mating signals. When presented with vibrational noise derived from wind males and females reduce their signaling behavior. However, individuals use strategies such as gap detection, which allow communication to …
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Index, Individual Trait, and Tandem Selection to Improve a Maize Synthetic for Yield, Corn Borer, and Disease Traits
… between pairs of traits, to construct two selection indexes designed to improve the synthetic for yield and resistance to CB and common Illinois maize diseases simultaneously, to predict gain from selection, and to determine adequate numbers of replicates and plants per plot for half-sib …
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The Effect of Isolation by Waterfalls and Dams on Stream Fish Morphology
<p>Large dams with upstream reservoirs can cause divergent selection in fish morphology; however, the effect of isolation from small dams without upstream reservoirs is largely unknown. This study investigated the effects of isolation on stream fish body morphology and the related effect of …
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Characterizing Compensatory Effects of Silymarin on Gossypol Toxicosis in Lines of Chickens Divergently Selected for Humoral Immune Response
… The second objective was to determine if divergent selection for humoral immune response would have an impact on the ability of the chicken to cope with gossypol toxicosis. Two preliminary studies were conducted. One determined basal activities of liver detoxification enzymes at various …
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Development of Genomic Resources for the Evaluation of Red Snapper, an Emerging Species Candidate for Marine Aquaculture and Stock Enhancement
… taxa. These results, coupled with the finding of divergent selection impacting several genomic regions during sliding window analysis, suggests that northern and southern red snapper should, at minimum, be managed as distinct population segments. Little evidence of population subdivision was found …
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Genomics of Climatic Adaptation in Populus Trichocarapa
… climate, and geography, which suggested climatic selection driving adaptation of these populations to local environments. We subsequently combined genotype-phenotype association tests with sliding window analysis and identified regions strongly associated with these adaptive traits. We also …
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Genetic variation in fast-evolving East African cichlid fishes: an evolutionary perspective
… evolution of microRNA regulation, and found that divergent selection on miRNA target sites may have led to differential gene expression, which contributed to the diversification of cichlid species. Overall, the patterns of cichlid genetic variation seem to be dominated by the phenomena of …
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The genomic basis of species barriers in Heliconius butterflies
… duplication and identify loci putatively under divergent selection that may play a role in species divergence and speciation. Secondly, I quantify sexually dimorphic expression in H. melpomene, and calculate rates of molecular evolution between H. melpomene and H. erato. Thirdly, I identify …
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Adaptive radiation, speciation, and reproductive isolation in African weakly electric fish : (Genus Campylomormyrus, Mormyridae, Teleostei)
… of weakly electric fish triggered by sexual selection via assortative mating due to differences in EOD characteristics, but caused by a divergent selection of morphological traits correlated with the feeding ecology.
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The effects of habitat on phenotype, growth and fitness in New Zealand triplefin fishes (Family: Tripterygiidae)
… The main factors associated with driving selection pressures were wave exposure and microhabitat type, and the former was consistently evident across all traits measured. Additionally, plasticity was shown to be the mechanism responsible for the observed morphological variation in F. …
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Genotype by feeding regimen interactions in growth selected chickens
… lines of which 2 had undergone 32 generations of divergent selection for 56-day body weight and 2 were their sublines in which selection has been relaxed for 5 generations. Mild feed restriction of the broiler line from 7 to 27 days of age reduced carcass fat and heterophil:lymphocyte ratios, and …
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Genetic analyses of reproductive behavior in the domestic fowl and the Japanese quail
… lines that had undergone over 20 generations of divergent selection for high and low mating frequency and the random bred control population from which the selected lines originated. In the first experiment, fertility comparisons under natural and artificial mating situations were made over time …
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Genomics-Based Analysis of Antibody Response to Sheep Red Blood Cells in Chickens
… from parental lines in the 28th generation of divergent selection for low (L) and high (H) anti-SRBC. The mean anti-SRBC titers of the parental lines were significantly different, with 11.5 for H and 2.6 for L (P<0.05). That for the 4 groups of F2 progeny ranged from 6.3 to 7.5, while those of …
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