A molecular phylogenetic reappraisal of theGraphiumcomplex based on 18S rDNA sequences

Abstract

Based on nuclear encoded small subunit (18S) rDNA sequences, a taxonomic reappraisal of Graphium (anamorphic fungi) was undertaken using neighbour-joining (NJ) and fast DNA maximum likelihood (fastDNAml) methods and compared with traditional classifications. In common with Graphium putredinis, Graphium penicillioides (the lectotype species) was found to be related to the Microascales, not the Ophiostomatales as previously believed. Both species might be heterogenous and should be treated as species aggregates. The representative mode of conidiogenesis for these two species was nodular-annellidic, rather than the dense-annellidic mode characteristic of the synnematous ophiostomatalean anamorphs. Graphium is emended to be restricted to G. penicillioides, G. putredinis, and related synnematous anamorphs of Petriella and Pseudallescheria, and a nomenclator for the nine species presently accepted in Graphium is presented. Pesotum, originally characterized mainly by sympodial conidiogenesis, is emended to include synnematous anamorphs of Ophiostoma species formerly included in a variety of genera with sympodial to dense-annellidic conidiogenesis. Eight new combinations in Pesotum are included in a nomenclator for the 26 species currently known. Three new combinations from Ceratocystis to Ophiostoma are proposed for species with Pesotum anamorphs. The holomorph of Graphium calicioides has affinities to the black yeasts and should be classified in the Chaetothyriales. However, the critical morphological, loculoascomycetous characters of the teleomorph are not completely documented. Interpreted from the molecular context, the morphological similarities between these three groups of anamorphs are homoplasies and examples of convergent evolution.Key words: Chaetothyriales, Graphium, Microascales, Ophiostomatales, Pesotum, 18S (SSU) rDNA sequences.