Phialophora and related dematiaceous genera: A molecular phylogenetic and taxonomic study.

摘要

Members of many anamorphic genera of fungi appear to be closely related based on a limited number of morphological characters. Identification can be difficult. Compounding this problem is the fact that many genera are pleomorphic and produce synanamorphs. In this study, the phylogenetic relationships among human pathogenic and saprobic species in the genera Cladophialophora, Cladosporium, Exophiala, Fonsecaea, Hortaea, Leptodontidium, Phialophora, Ramichloridium, Rhinocladiella and Wangiella were determined using nucleotide sequences of the ribosomal DNA 5.8S gene and the surrounding internal transcribed spacers. Sequence data were analyzed using parsimony and distance methods. Phylogenetic analysis showed that: (1) Morphological characters (specifically mode of conidiogenesis, conidium size and shape, etc.), while useful for delineation of genera and species taxonomically, are not necessarily good phylogenetic characters. (2) The genus Phialophora as presently conceived is a heterogeneous assemblage of morphologically similar, yet phylogenetically divergent taxa. (3) Isolates in the genera Fonsecaea and Cladophialophora are closely related. (4) Cladophialophora brevicatenata is not closely phylogenetically related to any of the other species in Cladophialophora. (5) Isolates of Wangiella dermatitidis group together forming a clade separate from isolates of Exophiala. (6) The taxon Phialophora heteromorpha is found to be phylogenetically related to Wangiella, therefore the combination Wangiella heteromorpha is proposed. (7) The separation of Hortaea away from Exophiala is confirmed. (8) Leptodontidium is shown to be neither closely related to Ramichloridium nor Rhinocladiella, but is instead interspersed among several isolates of Phialophora. (9) The name Rhinocladiella anceps is preferable to Ramichloridium anceps since it grouped with Rhinocladiella atrovirens. Isolates of Phialophora were found in each of the three main clades in the analyses. Therefore, a proposal is presented for a reorganization of members of Phialophora along phylogenetically related lines. Overall, the rDNA sequence data have provided a better understanding of the phylogenetics of these fungi. The present study demonstrates the utility of molecular characters to examine the validity of taxonomic and phylogenetic results obtained from other data sets.