The sequestrate genus Rosbeeva T.Lebel & Orihara gen. nov. (Boletaceae) from Australasia and Japan: new species and new combinations

Abstract

The sequestrate genus Chamonixia has been shown to have affinities to the Boletales, in particular the genus Leccinum. Australasian and Japanese species of Chamonixia were examined using morphological and molecular (ITS and nLSU rDNA) data and found to also have affinities with Leccinum and Leccinellum, however they form a distinct clade separate from the European type species C. caespitosa Rolland and North American species. A new genus, Rosbeeva T.Lebel & Orihara gen. nov., is proposed for the Australasian, Japanese and Chinese taxa. The species R. mucosa (Petri) T.Lebel comb. nov. is restricted in distribution to Singapore and Borneo, and R. pachyderma (Zeller & C.W. Dodge) T.Lebel comb. nov. to New Zealand, with Australian collections considered to belong to a revised R. vittatispora (G.W.Beaton, Pegler & T.W.K.Young) T.Lebel comb. nov. or a new species R. westraliensis T. Lebel sp. nov. The Chinese species R. bispora (B.C.Zhang & Y.N.Yu) T.Lebel & Orihara comb. nov is transferred to the new genus based upon morphological data. Two new species from Japan, Rosbeeva eucyanea Orihara and R. griseovelutina Orihara, are also described and illustrated. A key to all species of Rosbeeva is provided. Due to the highly modified gastroid sporocarp forms of both Chamonixia and Rosbeeva, many macroscopic characters of use in agaricoid taxonomy are difficult to interpret. However, color change and texture of sporocarps are of some use to distinguish genera and species. Microscopic characters such as spore shape, dimensions, and ornamentation, and pileipellis and hymenophoral trama structure, are essential for determining genera and species.