Systematics of thePhialophora verrucosacomplex: new insights from analyses of β-tubulin, large subunit nuclear rDNA and ITS sequencesThis paper is one of a selection of papers published in the Special Issue on Systematics Research.

Abstract

Phialophora Medlar, as defined currently, is a genus encompassing melanized, anamorphic Ascomycota that produce one-celled conidia from phialides with distinct, darkened collarettes. The type species, Phialophora verrucosa Medlar, is closely related to Phialophora americana (Nannf.) S. Hughes, the anamorph of Capronia semiimmersa (Candoussau & Sulmont) Untereiner & Naveau (Herpotrichiellaceae, Chaetothyriales). To confirm that P. americana and P. verrucosa are distinct taxa, and to examine their phylogenetic relationships to species of Capronia and other representatives of the Chaetothyriales, we sequenced portions of the β-tubulin gene and nuclear ribosomal RNA cistron (ITS and LSU rDNA). We also compared isolates of P. americana grown on a number of media. Isolates of C. semiimmersa, Capronia svrcekiana Réblová, and P. americana produced phialides bearing deep, vase-shaped collarettes and formed a strongly supported clade that did not include P. verrucosa in a phylogeny inferred from the combined β-tubulin–ITS–LSU dataset. Capronia svrcekiana was found to be conspecific with C. semiimmersa based on the comparison of cultural, micromorphological, and molecular characters. In the LSU phylogeny, three recently described species of Phialophora ( Phialophora europaea de Hoog et al., Phialophora reptans de Hoog, and Phialophora sessilis de Hoog) were grouped outside of the clade containing sampled members of the Herpotrichiellaceae. While the position of these species in the Chaetothyriales remained unresolved, it was evident that P. europaea, P. reptans, and P. sessilis are not members of the P. verrucosa complex.