Transfer of two Helicoma species to Troposporella based on molecular and morphological data

Abstract

Previous molecular data demonstrated that, although Helicoma is polyphyletic, most species in the genus, including the type Helicoma muelleri, are in the Tubeufiaceae. Here, we use analysis of the small subunit and internal transcribed spacers (ITS) rDNA regions to show that two species, H. monilipes and H. olivaceum, are phylogenetically distant from the type, branching outside of the Tubeufiaceae near Troposporella fumosa in a basal clade of the Dothideomycetes. The phylogeny does not support the recent transfer of T. fumosa to Helicoma. Instead, based on the molecular evidence as well as the examination of cultures and type specimens, Troposporella is reinstated at the generic level, and Helicoma monilipes and Helicoma olivaceum are transferred to Troposporella. All three Troposporella species share the production of helicoid conidia borne on sporodochial conidiomata from blastic conidiogenous cells. A key to accepted species is provided.