Phylogenetic analysis of the non-pathogenic genus Spiromastix (Onygenaceae) and related onygenalean taxa based on large subunit ribosomal DNA sequences

Abstract

The phylogenetic positioning of the non-pathogenic genus Spiromastix in the Onygenales was studied based on large subunit rDNA (LSU rDNA) partial sequences (ca. 570 bp.). Four Spiromastix species and 28 representative taxa of the Onygenales were newly sequenced. Phylogenetic trees were constructed by the neighbor-joining (NJ) method and evaluated by the maximum parsimony (MP) method with the data of 13 taxa retrieved from DNA databases. Spiromastix and dimorphic systemic pathogens, Ajellomyces and Paracoccidioides, appear to be a monophyletic group with 74% bootstrap probability (BP) in the NJ tree constructed with the representative taxa of the Onygenales. The tree topology was concordant with the NJ tree based on SSU rDNA sequences of our previous work and corresponded to the classification system of the Onygenales by Currah (1985) and its minor modification by Udagawa (1997) with the exception of the classification of the Onygenaceae. The Onygeneceae sensu Udagawa may still be polyphyletic, since three independent lineages were recognized. The taxa forming helicoid peridial appendages were localized to two clades on the tree. The topology of the NJ tree constructed with Spiromastix and its close relatives suggested that the helicoid peridial appendages were apomorphic and acquired independently in the two clades of the Onygenales.