Systematics Of Freshwater Sordariomycetes And Anamorphic Fungi & Biodiversity Of Freshwater Fungi Referring To Human Disturbance

Freshwater fungi were defined as"fungi that the whole or part of their life cycle rely on freshwater". Freshwater fungi are an ecological group, with high diversity. Freshwater fungi play an important role in ecosystem. They can decompose organic substrata in freshwater, and their mycelium are involved into the food web when grazed by animals. As a rarely exploited bio-resource, freshwater fungi have great potential in producing various and useful metabolites. Resource investigation and systematic research are essential to the research and application of freshwater fungi. Numerous species new to science are supposed to be encountered in the future study. The most poorly reported areas are Africa, Australia, China, South America and the tropic areas all over the world. Freshwater fungi have been classified according to morphological characters for a long time; and few taxa have been studied by molecular method. In this study, we aim to investigate freshwater fungi, construct more natural systems of freshwater Sordariomycetes and anamorphic fungi and study on fungal diversity referring to human disturbance.The freshwater fungi were investigated in Thailand and Jiangxi, Yunnan and Guizhou provinces of China to study their systematics and diversity. The submerged woody samples were collected from various freshwater habitats including streams, lakes, ponds and ditches. The fungi on submerged wood were identified and isolated, and 18S, 28S and ITS sequences were analyzed to study the systematics of freshwater fungi. The main results in this study are listed below.1. In this study, 875 samples were collected, 148 dry specimens and 186 slides were deposited, and 174 fungal strains were isolated; 165 fungal species belonging to 63 genera were identified. The collecting sites were mainly in the tropic areas (e.g. Thailand, Mengla) and poorly reported areas in China (e.g. Guizhou province, Jiangxi province).2. Some taxa of freshwater Sordariomycetes were relocated according to the molecular and morphological studies in this paper. The more natural classification system of freshwater Sordariomycetes was achieved through multilocus phylogenetic study, and the morphological characters of all the genera of freshwater Sordariomycetes were listed. Keys to every subphylum, orders, families and genera were provided in this thesis. Annulatascaceae is the most representative family as most species of this family were reported from freshwater habitats. However, the systematics placement of Annulatascaceae has not been resolved for a long time. We suggest that Annulatascaceae should be one family in Ophiostomatales according to results of combined morphological and molecular studies in this study. The phylogenetic trees of Nectriaceae and Halosphaeriaceae based on 28S and 18S sequences were constructed to analyze the systematics placement of the families and the relationships among the genera in the families. The genera Ophioceras and Pseudohalonectria are similar in morphology. However, the results of phylogenetic study based on 28S and ITS sequences present prominent phylogenetic distance between the two genera. The systematics placement of Ascolacicola, Ascotaiwania and Clohiesia have been long discussed, and the results of phylogenetic study based on 18S and 28S sequences in this study show that they are Sordariomycetidae incertae sedis. The classification system constructed in this study is essential for future study on freshwater Sordariomycetes.3. The morphological characters and keys to species of twenty common freshwater anamorphic genera were listed and constructed in this paper, and some of the genera were integrated into the teleomorphic system. The phylogenetic trees of Acrodictys, Bactrodesmium, Canalisporium, Dactylaria, Dictyochaeta, Dictyosporium, Ellisembia and Exserticlava were generated, and these genera were integrated into the teleomorphic system. The phylogenetic relationships among species in these 8 genera were discussed according to the results of combined molecular and morphological studies.4. One new freshwater genus Aquanectria was collected and described in this study. The results of combined molecular and morphological studies show that Aquanectria belongs to Nectriaceae. Eight new species belonging to Sordariomycetes, i.e Aquanectria mengla,Lignincola curvispora,Ophioceras menglensis,Pseudohalonectria fusiformia,P. mengla,Annulatascus menglensis , Aqualignicola vagina and Ascitendus lacicolus and 7 new anamorphic species i.e. Acrogenospora ellipsoidea, Dactylaria ellipsoidea, D. fossa, D. ramose, D. ellipsoidea, Vanakripa menglensis and Xylomyces ramosis were collected and described in this study. The systematics placement and differences among similar species were discussed according to the results of molecular and morphological studies.5. Human disturbance can affect the communities and diversity of freshwater fungi. The fungal diversity and communities in the stream and artificial lake in Mushroom Research Center in Thailand were studies in this paper. Seventeen teleomorphic ascomycetes and 51 anamorphic fungi were identified in the two studied sites. Analysis of ecological data shows that damming decreases the diversity of freshwater fungi and changes the fungal communities. We also compared the fungal diversity between lentic and lotic freshwater habitats in this paper; the results show that the fungal diversity is lower in the lentic freshwater habitats than in the lotic freshwater habitats. The still waters with low oxygen may have reduced the number of fungi present.It is an initial study on systematics of freshwater Sordariomycetes by the methods combined with molecular and morphologic studies, wihich results in a more natural system of freshwater Sordariomycetes. The characters of 20 common freshwater hyphomycetes are listed in this thesis; and the genera are inetegrated into the teleomorphic systems according to the results of molecular studies and anamorph-teleomorph connection studies. The results of this study are imorptant references for future studies on freshwater fungi.The results of this study show that there are numerous undescribed species in freshwater habitats, more studies on investigation, systematics and ecology of freshwater fungi should be conducted to increase our knowledge about this highly diverse group of fungi.