Typification of Sphaeria sinensis to precisely fix the application of the name of the economically important Chinese caterpillar fungus, Ophiocordyceps sinensis

Abstract

AbstractThere is a long‐standing need to fix the application of the name Sphaeria sinensis, basionym of the economically important Chinese caterpillar fungus Ophiocordyceps sinensis, at the molecular level. The fungus was described by Berkeley in 1843, and is now harvested in the Tibetan Plateau (including the Himalayas). This need arises because of the existence of putative later synonyms in need of confirmation, existence of multiple haplotypes, occurrence of diverged ITS paralogs, and need to be confident of the identity of commercially grown cultures of the asexual morph. Here we report the rediscovery of original material in a spirit collection originally held in the Natural History Museum London but now at the Royal Botanic Gardens Kew. There are also three undated collections under this name in the Kew Fungarium from Berkeley's herbarium, and another with the name of Reeves, who sent the material to the U.K., but which originated from Hooker's herbarium. There is no proof that any of these four dried collections were used by Berkeley when describing the species. The collection in the spirit jar and the published illustration are the only original materials, and that in the spirit jar is designated as lectotype here; the collection from Hooker's herbarium may be an isolectotype but it was not studied by Berkeley. As no DNA would have been recoverable from the spirit collection, we endeavoured to extract DNA from two of the dried collections. Routine DNA amplification did not yield any ITS fragments, so a metagenomic approach was used and the collection from Hooker's herbarium yielded an entire 3189 bp ITS sequence most similar to those of the haplotype that predominates in the major distributional area of the fungus. A rich modern collection from the core region of the fungus in China, with ample stromata of the fungus on the host, and the ITS sequence matching that obtained from the dried specimen from Hooker's herbarium, is designated as epitype to unequivocally fix the application of the name. Ex‐type living cultures from the epitype were obtained and are also being maintained.