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Date of Award

6-2006

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Supervisor

Jianping Xu

Language

English

Abstract

Recent population genetic studies have revealed that there are multiple natural hybridizations among divergent lineages in the human pathogenic fungus Cryptococcus neoformans. However, the biological and phenotypic effects of such hybridization are little understood. In this study, we constructed a laboratory cross between two genetically diverged strains; chosen because they differed in growth at different temperature and medium conditions and in their susceptibilities to the common antifungal drug Fluconazole. Our analyses indicated evidence of environment-specific outbreeding depression and intermediate phenotypes in the hybrid population of C. neoformans. A variable number of progeny displayed evidence of transgressive segregation. With increasing drug concentration, the relative fitness of transgressive hybrids also increased. The analyses showed that the progeny population had a greater phenotypic plasticity than the parental strains. Our study suggested that hybridization can playa significant role in the evolution of this important human pathogenic fungus.

McMaster University Library

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