Systematics and evolution of bark-inhabiting species of the Gnomoniaceae (Diaporthales, Ascomycota) with emphasis on the genera Cryptosporella and Plagiostoma.

摘要

The Gnomoniaceae (Diaporthales, Ascomycota) comprise microfungi that grow on leaves and woody tissues of a range of plant families, mostly hardwood trees from temperate zones of the northern hemisphere. Many dominant endophytes of trees in North America and Europe are species of Gnomoniaceae. Several emerging and devastating diseases of forest trees are caused by pathogenic species of Gnomoniaceae. Despite their abundance and impact in forest ecosystems, the Gnomoniaceae have not received modern taxonomic review and phylogenetic study. Most morphologically defined genera in this family are polyphyletic when analyzed with molecular data, therefore new circumscription of genera is needed.;The objectives of this work are to: (1) define monophyletic genera and determine species limits for bark-inhabiting fungi in the Gnomoniaceae; and (2) infer the phylogeny of bark-inhabiting genera of Gnomoniaceae (e.g. Cryptosporella, and Plagiostoma). To achieve these objectives fresh specimens were collected in locations in Europe, North, Central and South America, and China. Specimens from herbaria and living collections from culture repositories were included in the study. The methods integrate a comparison of morphological characters of specimens in natural substrates such as the arrangement, shape, and size of perithecia and the shape and size of asci and ascospores with molecular characters, i.e. DNA sequences from multiple loci (beta-tubulin, ITS, LSU, rpb2, and tef1-alpha) analyzed by Bayesian inference, Maximum Likelihood, Neighbor Joining, and Parsimony.;This research resulted in the recircumscription of the genera Cryptosporella and Plagiostoma and the definition of a new genus Occultocarpon gen. nov. A total of 32 taxonomic novelties were defined. More specifically, 17 new species, a new genus of bark-inhabiting Gnomoniaceae, and 14 new name combinations were described. This project has shown that host identity is a better predictor than geographic location for finding species of Gnomoniaceae. By documenting species of Gnomoniaceae from the Neotropics, South America, and subtropical China, results from this project have changed the previous assumption that the Gnomoniaceae only occur in temperate zones of the Northern Hemisphere. Finally, the phylogenies obtained suggest a long evolutionary relationship between Cryptosporella and Betulaceae and a subclade of Plagiostoma with the Salicaceae.