Rare and undersampled dimorphic basidiomycetes

The diversity of yeasts has grown rapidly as the discovery of new species has benefited from intensified sampling and largely improved identification techniques. An environmental study typically reports the isolation of yeast species, some of which are new to science. Rare species represented by a few isolates often do not result in a taxonomic description. Nucleic acid sequences from these undescribed yeasts remain in public sequence databases, often without a proper taxonomic placement. This study presents a constrained phylogenetic analysis for many rare yeasts from unpublished but publicly available DNA sequences and from studies previously conducted by the authors of this work. We demonstrate that single isolates are an important source of taxonomic findings such as including new genera and species. Independent surveys performed during the last 20 years on a large geographic scale yielded a number of single strains, which were proved to be conspecific in the phylogenetic analyses presented here. The following new species were resolved and described: Vustinia terrea Kachalkin, Turchetti & Yurkov gen. nov. et sp. nov.; Udeniomyces caspiensis Kachalkin sp. nov.; Udeniomyces orazovii Kachalkin sp. nov.; Tausonia rosea Kachalkin sp. nov.; Itersonilia diksonensis Kachalkin sp. nov.; Krasilnikovozyma fibulata Glushakova & Kachalkin, Kwoniella fici Turchetti sp. nov.; Heterocephalacria fruticeti f.a. Carvalho, Roehl, Yurkov & Sampaio sp. nov.; Heterocephalacria gelida f.a. Turchetti & Kachalkin sp. nov.; Heterocephalacria hypogea f.a. Carvalho, Roehl, Yurkov & Sampaio sp. nov.; Heterocephalacria lusitanica f.a. Inacio, Carvalho, Roehl, Yurkov & Sampaio sp. nov.; Piskurozyma arborea Yurkov, Kachalkin, Mašínová & Baldrian sp. nov.; Piskurozyma silvicultrix Turchetti, Mašínová, Baldrian & Yurkov sp. nov.; Piskurozyma stramentorum Yurkov, Mašínová & Baldrian sp. nov.; Naganishia nivalis Turchetti sp. nov.; and Yurkovia nerthusi Yurkov & Begerow, sp. nov. In addition, two new combinations were proposed Krasilnikovozyma curviuscula (Babeva, Lisichkina, Reshetova & Danilevich) Yurkov, Kachalkin & Sampaio comb. nov. and Hannaella taiwanensis (F.L. Lee & C.H. Huang) Yurkov comb. nov. The order Cyphobasidiales T. Spribille & H. Mayrhofer is rejected in favor of the older name Erythrobasidiales R. Bauer, Begerow, J.P. Sampaio, M. Weiss & Oberwinkler. Other potential novel species identified in this paper await future description. Phylogenetic placement of yet unpublished sequences is believed to facilitate species descriptions and improve classification of yeasts from environmental sequence libraries.