@ARTICLE{TreeBASE2Ref15862, author = {Kerstin Hoffmann and Sabrina Discher and Kerstin Voigt}, title = {Revision of the genus Absidia (Mucorales, Zygomycetes) based on physiological, phylogenetic and morphological characters: Thermotolerant Absidia spp. form a coherent group, the Mycocladiaceae fam. nov}, year = {2007}, keywords = {}, doi = {}, url = {}, pmid = {}, journal = {Mycological Research}, volume = {}, number = {}, pages = {}, abstract = {The genus Absidia comprise ubiquitously distributed soil fungi inhabiting different growth temperature optima ranging from 20 ?C to 42 ?C. While few of the mesophilic species imply biotechnological importance in biotransformation of steroids or as producers of rennin-like components, the species with higher growth temperature optima are of clinical relevance as opportunistic human pathogens. The aim of this study was to investigate the phylogenetic relationships between these species and to establish a revision of their systematics. For this purpose single and combined genealogies based on distance, maximum parsimony, maximum likelihood and Bayesian analyses of aligned nucleotide sequences of the nuclear-encoded genes for actin (act) and for the 5.8S ribosomal RNA flanked by the internal transcribed spacer (ITS) regions 1 and 2 (comprising 807 and 828 characters, respectively) of 16 Absidia species were reconstructed. The phylogenetic reconstructions suggest a trichotomy of the Absidia genus consisting of a mesophilic, a fast-growing thermotolerant and a slowly-growing mycoparasitic Absidia group. The trichotomous phylogenetic grouping is concordant with the morphology of the zygospores, which are zygotes resulting from sexual conjugation between two compatible mating partners. Whereas the mesophilic group comprises the majority of absidiaceaeous species forming sterile hairlike, mycelial appendages on the suspensors of their zygospores, the thermotolerant group is characterised by the formation of smooth-walled and the mycoparasitic group, namely Absidia parricida and A. zychae, by Mucor-like rough-walled zygospores. Based on the phylogenetic coherence of mesophilic and thermotolerant Absidia species, we propose to separate both groups into two distinct genera, Absidia for the mesophilic Absidia species resembling the Absidiaceae and Mycocladus for the thermotolerant species A. corymbifera, A. blakesleeana and A. hyalospora. Because Mycocladus is physiologically, phylogenetically and morphologically distinct from the Absidiaceae sensu stricto we suggest to classify them into a separate family, the Mycocladiaceae fam. nov. which comprises the three species Mycocladus corymbifer, M. blakesleeanus and M. hyalospora.} }

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