Use of holomorph characters to delimit Microascus nidicola and M. soppii sp. nov., with notes on the genus Pithoascus

Abstract

Several isolates of a perithecial microascaceous ascomycete having falcate ascospores and a Scopulariopsis anamorph were obtained from rotting wood in the boreal forest of Alberta, Canada. Additional isolates appeared conspecific based on anamorphic characters, but failed to produce a teleomorph. These isolates showed similarities to Microascus nidicola (type species of the genus Pithoascus) and Scopulariopsis flava. Sexual compatibility systems were investigated to establish holomorph concepts for these taxa. The teleomorph obtained in mating trials among anamorphic isolates was identical to that of self-fertile isolates. The new heterothallic species M. soppii is described. The anamorph is S. soppii. Single ascospore isolates derived from M. nidicola demonstrated homothallism and lacked an anamorph. Scopulariopsis flava (basionym Acaulium flavum) is considered a nomen dubium. Generic concepts of Pithoascus are evaluated and the genus is treated as a synonym of Microascus. Pithoascus stoveri is transferred as M. stoveri comb. nov.

• anamorph-teleomorph connections
• Ascomycota
• hyphomycetes
• Microascaceae
• Scopulariopsis

Curators and staff of the various culture collections that provided material for this study are sincerely thanked. Appreciation is expressed to Ming Chen for SEM, M. Hertwig-Jaksch for correcting the Latin, and to Linda Abbott and Arlene Flis for assistance with various technical aspects of this work. This work was part of a Ph.D. dissertation by S. P. Abbott who was supported by scholarships from Izaac Walton Killam Memorial Fund and Natural Sciences and Engineering Research Council of Canada (NSERC). Field and laboratory work was supported by awards from the Challenge Grants in Biodiversity Program, jointly sponsored by the Alberta Conservation Association and the University of Alberta Dept. of Biological Sciences to SA and TL. Research grants from NSERC to LS and the Myron Backus Award from the Mycological Society of America to SA are gratefully acknowledged.