Biology, ecology and evolution of the family Gigasporaceae, arbuscular mycorrhizal fungi (Glomeromycota)

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Biology, ecology and evolution of the family Gigasporaceae, arbuscular mycorrhizal fungi (Glomeromycota)

Type: Doctoral Thesis
Title: Biology, ecology and evolution of the family Gigasporaceae, arbuscular mycorrhizal fungi (Glomeromycota)
Author: Souza, Francisco Adriano de
Publisher: Institute of Biology, Faculty of Mathematics & Natural Sciences, Leiden University
Issue Date: 2005-10-10
Keywords: Glomeromycota
Life History strategy
Parasexual recombination
Root organ culture
rDNA polymorphism
Plant ecology
Abstract: Research described in this thesis focused on biological, ecological and evolutionary aspects of Arbuscular Mycorrhizal Fungi (AMF), and in particular of the family Gigasporaceae (Gigaspora and Scutellospora, genera). This study had two major objectives. The first objective was to obtain better knowledge about the life history strategies (LHS) of Gigasporaceae, and the second objective was to study the intragenomic polymorphism of the ribosomal rDNA copies in order to understand its origin and to test the use of such polymorphism to discriminate between closely related species. The LHS patterns observed for the Gigasporaceae species studied suggests that they behave like K-strategists, i.e. organisms adapted to live at stable and predictable environments, as compared to Glomeraceae species that form single spores in the soil. Based on LHS patterns of Gigasporaceae an hypotheses that those species will be negatively selected in disturbed ecosystems have been formulated. Although intraspecific rDNA polymorphism in Gigasporaceae has been previously reported, this study, for the first time, systematically describes this heterogeneity and analyses this phenomenon with respect to Gigasporaceae phylogeny and evolution. It has been demonstrated that the intragenomic polymorphism of the rDNA copies can be used to differentiate species and in the case of Gigaspora even isolates. The phylogenetic analysis of inter and intragenomic rDNA polymorphism of closely related Gigaspora species strongly suggested that reticulated evolution, characterized by occasional hybridization or horizontal gene transfer between two species, played a significant role in evolution of this asexual group of fungi, via parasexual recombination. In addition, a molecular method was developed to assess Gigasporaceae diversity in environmental samples.
Description: Promotores: J.A. van Veen, G.A. Kowalchuk. Co-promotor: E. Smit.
With summaries in Dutch and Portuguese
Faculty: Faculteit der Wiskunde en Natuurwetenschappen
Citation: de Souza, F.A., 2005. Doctoral thesis, Leiden university
Sponsor: The study described in this thesis was performed at the section Plant Ecology of the Institute of Biology Leiden of Leiden University; the practical work was performed at the Netherlands Institute of Ecology (NIOO-KNAW), Centre for Terrestrial Ecology, Heteren. The financial support for this study was provided by the Brazilian Council for Scientific and Technological Development (CNPq), project 200850/98-9, Brazil.

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