Taxonomy and Phylogeny of Ascomycota in Freshwater Plants

Abstract

Freshwater plants are ubiquitous in the earth and a large group of fungi are saprobic or parasitic in these plants, including submerged wood. Freshwater Dothideomycetes are a highly diverse group of fungi, which are mostly saprobic in freshwater habitats worldwide. They are important decomposers of submerged woody debris and leaves in water. In this thesis, the genera of freshwater Dothideomycetes with notes and keys on species are outlined. Based on multigene analyses and morphology, nine new genera are introduced, viz. Aquimassariosphaeria, Aquatospora, Aquihelicascus, Fusiformiseptata, Neohelicascus, Neojahnula, Pseudojahnula, Purpureofaciens, Submersispora; 33 new species, viz. Acrocalymma bipolare, Aquimassariosphaeria kunmingensis, Aquatospora cylindrica, Aquihelicascus songkhlaensis, A. yunnanensis, Ascagilis submersa, A. thailandensis, Bambusicola aquatica, Caryospora submersa, Dictyocheirospora thailandica, Fusiformiseptata crocea, Helicosporium thailandense, Hongkongmyces aquaticus, Lentistoma aquaticum, Lentithecium kunmingense, Lindgomyces aquaticus, Longipedicellata aquatica, Neohelicascus submersus, Neohelicomyces dehongensis, N. thailandicus, Neohelicosporium submersum, Nigrograna aquatica, Occultibambusa kunmingensis, Parabambusicola aquatica, Pseudoasteromassaria aquatica, Pseudoastrosphaeriella aquatica, Pseudoxylomyces aquaticus, Purpureofaciens aquatica, Roussoella aquatica, Shrungabeeja aquatica, Submersispora variabilis, Tetraploa puzheheiensis, T. yunnanensis; 16 new combinations, viz. Aquimassariosphaeria typhicola, Aquihelicascus thalassioideus, Ascagilis guttulaspora, A. queenslandica, A. seychellensis, A. sunyatsenii, Ernakulamia xishuangbannaensis, Neohelicascus aquaticus, N. chiangraiensis, N. egyptiacus, N. elaterascus, N. gallicus, N. unilocularis, N. uniseptatus, Neojahnula australiensis, Pseudojahnula potamophila; 17 new geographical and habitat records, viz. Aliquandostipite khaoyaiensis, Aquastroma magniostiolata, Caryospora aquatica, C. quercus, Dendryphiella vinosa, Ernakulamia cochinensis, Fissuroma neoaggregatum, Helicotruncatum palmigenum, Jahnula rostrata, Neoroussoella bambusae, N. leucaenae, Occultibambusa pustula, Paramonodictys solitarius, Pleopunctum pseudoellipsoideum, Pseudocapulatispora longiappendiculata, Seriascoma didymosporum, Shrungabeeja vadirajensis and ten new collections from China and Thailand, viz. Amniculicola guttulata, Aquaphila albicans, Berkleasmium latisporum, Clohesyomyces aquaticus, Dictyocheirospora rotunda, Flabellascoma fusiforme, Pseudoastrosphaeriella bambusae, Pseudoxylomyces elegans, Tubeufia aquatica and T. cylindrothecia. Six orders, 43 families and 145 genera which belong to freshwater Dothideomycetes are reviewed. Of these, 46 genera occur exclusively in freshwater habitats. A world map illustrates the distribution of freshwater Dothideomycetes. Annulatascaceae is an interesting and taxonomically confused family in Sordariomycetes as some family members are scattered in different orders/families in Diaporthomycetidae. Although taxonomic changes have been done for some genera, many are still questionable or their placements are unstable as lacking DNA sequence data. In this thesis, a survey of freshwater annulatascaceae-like species results in 23 new taxa, including five new genera (i.e. Aquidictyospora, Fusoidigranularius, Longivarius, Neodiluviicola and Obliquiminima) and 18 new species (i.e. Annulatascus chiangmaiensis, A. nakhonensis, A. songkhlaensis, Aquapteridospora aquatica, Aquidictyospora appendicula, Cancellidium thailandense, Conlarium subglobosum, Dictyosporella chiangmaiensis, D. ellipsoidea, Distoseptispora fasciculata, D. saprophytica, D. songkhlata, Fluminicola striata, Junewangia thailandica, Obliquiminima hyalina, Sporidesmiella obovoidia, Sporidesmium appendiculatum and S. chiangmaiense). Annulatascus aquatorba and A. nilensis are excluded from Annulatascus sensu stricto, and placed in two new genera Longivarius and Fusoidigranularius, respectively. Diluviicola capensis is a new geographical record in Thailand, and D. aquatica is transferred to a new genus Neodiluviicola as N. aquatica. Obliquiminima which is morphologically similar to Ayria is introduced as a new sexual genus in Cancellidiaceae. All taxa are identified based on multigene analyses of combined LSU, ITS, TEF and RPB2 sequence data and morphological comparison. An updated review for several orders, families and genera in Annulatascaceae and its sexual and asexual allies, is provided under each entry based on our new data. Two new species which are similar to Bactrodesmium longisporum in Eurotiomycetes were collected from submerged wood in the Greater Mekong Subregion. Pseudobactrodesmium gen. nov. is introduced to accommodate the new species P. aquaticum and P. chiangmaiensis, and B. longisporum is transferred to this genus. Pseudobactrodesmium aquaticum has longer conidia than P. chiangmaiensis. The placement of Pseudobactrodesmium in Dactylosporaceae (Eurotiomycetes) is a novel finding based on analyses of combined LSU, SSU, ITS and RPB2 sequence data. Our study reveals that Pseudobactrodesmium is likely to be a speciose genus with different species in streams around the world. Nelumbo is a genus of water plants and commonly known as lotus. Nelumbo nucifera is native to India and Vietnam, and N. lutea is native to North America and the Caribbean. Lotus is an important water plant worldwide, including in Thailand as a vegetable and an ornamental plant. It is also a popular traditional medicinal plant with great economic value in South-East Asia. Based on preliminary review of fungal diseases on lotus, N. nucifera is the most common host which is easily infected by fungi, while seldom report about fungal diseases on N. lutea. Little information is known about deseases on Lotus in Thailand with study on modern taxonomy and phylogeny. During a preliminary survey on fungal diseases on lotus, Ceratorhiza hydrophila is found on leaf spot of N. nucifera. Ceratorhiza hydrophila is described, illustrated and identified based on classical taxonomic and multigene (LSU and ITS) analysis.