Author : Vijaykrishna Dhanasekaran
Release : 2017-01-26
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Kind : eBook
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Book Synopsis Freshwater Fungi by : Vijaykrishna Dhanasekaran

Download or read book Freshwater Fungi written by Vijaykrishna Dhanasekaran. This book was released on 2017-01-26. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Freshwater Fungi: Biodiversity, Origins and Molecular Taxonomy" by Vijaykrishna, Dhanasekaran, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled FRESHWATER FUNGI: BIODIVERSITY, ORIGINS AND MOLECULAR TAXONOMY Submitted by Vijaykrishna Dhanasekaran for the degree of Doctor of Philosophy at The University of Hong Kong in October 2005 Freshwater ecosystems are in a constant interaction with the riparian environment surrounding them. Riparian vegetation is a major source of organic carbon to stream ecosystems. To determine the impact of riparian vegetation on the biodiversity of lignicolous freshwater fungi, fungi were sampled from five tropical streams of the Barron River catchment area in Atherton Tablelands, Queensland, Australia at sites identified as pristine, re-growth forest or agricultural. Fifty wood samples collected from each of 12 stream sites yielded 162 fungal taxa. The dominant ascomycetes were species of Annulatascus, Aquaticola (Annulatascaceae), Anthostomella (Xylariaceae), Massarina (Lophiostomataceae) and Savoryella (Sordariales incertae sedis). Species diversity was greatest in the pristine forest sites, followed by agricultural sites, while re-growth sites were least diverse. Species overlap was seen between all streams, and between the three types of riparian vegetation. Fungal species showed little habitat recurrence, although major changes were observed in species richness and abundance, with varying degrees of human disturbance. Phylogenetic studies suggest that freshwater ascomycetes have originated from terrestrial fungi. In this study, sequence analysis of the 18S rDNA coupled with Bayesian relaxed-clock methods are used to date the origin of freshwater fungi and also test their relationships with their terrestrial counterparts. Molecular analyses confirmed the phylogenetic evidence that they have originated from terrestrial fungi. The earliest possible date for fungi to adapt to freshwater conditions is estimated at 390 MYA. The adaptation to inhabit freshwater substrates appears to have occurred in several lineages through the course of time. Diversity studies have also resulted in some fungal taxa, that are new to science. Based on morphological characterisation and phylogenetic analyses of rDNA sequences, two new ascomycete genera and one new anamorphic genus have been established. These include Fusoidispora aquatica, Murisporium aquaticus and Pleurostomaphora ootheca. Molecular data were also used to resolve the taxonomic position of two genera, Phomatospora and Savoryella. Phylogenetic analyses based on 18S rDNA show that Phomatospora is closely related to the Magnaporthaceae and Savoryella belongs to the order Hypocreales. The phylogenetic relationships of several families within the Pleosporales (bitunicate ascomycetes) have also been determined. Combined sequence analyses of the 18S rDNA and 28S rDNA genes are used to assess the putative monophyly of families. The taxonomic concepts of three families, Lophiostomataceae, Massarinaceae and Melannomataceae were redefined and the phylogenetic significance of specific morphological characters in their classification was elucidated. DOI: 10.5353/th_b3201758 Subjects: Freshwater fungi - Australia - Queensland - Classification - Molecular aspects Biodiversity - Australia - Queensland