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Experimental evolution of Pseudomonas fluorescens in simple and complex environments

Determining the factors responsible for the origin and maintenance of diversity remains a difficult problem in evolutionary biology. There is extensive theoretical work which suggests that environmental heterogeneity plays a major role. This theory argues that diversification is ultimately due to divergent natural selection for alternative resources. In this thesis I investigate adaptation and the evolution of diversity in experimental populations of the asexual bacterium Pseudomonas fluorescens. In all experiments I introduce clonal isolates of Pseudomonas to a novel environment and allow evolution to occur through the substitution of random mutations. Adaptation can then be quantified by comparing evolved genotypes to the ancestor. These experiments show that when Pseudomonas is selected in a complex environment containing several resources, sympatric genotypes adapt to use different resources, leading to the evolution of genetically diverse populations. In environments containing just a single resource, most genotypes adapt to use the same resource and no such diversity is observed. Adaptation in the experimental populations is caused by the fixation of beneficial mutations of intermediate fitness effect. My results highlight the value of microbial model systems for answering evolutionary questions and provide strong evidence for the role of ecological factors in the origin of diversity.

Identiferoai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.97902
Date January 2005
CreatorsBarrett, Rowan Douglas Hilton.
PublisherMcGill University
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
LanguageEnglish
Detected LanguageEnglish
TypeElectronic Thesis or Dissertation
Formatapplication/pdf
CoverageMaster of Science (Department of Biology.)
Rights© Rowan Douglas Hilton Barrett, 2005
Relationalephsysno: 002335800, proquestno: AAIMR24612, Theses scanned by UMI/ProQuest.

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