Unique phylogenetic position of the African truffle-like fungus, Octaviania ivoryana (Boletaceae, Boletales), and the proposal of a new genus, Afrocastellanoa

ABSTRACT

The sequestrate (truffle-like) basidiomycete Octaviania ivoryana was originally described based on collections from Zimbabwe, Kenya, Guinea, and Senegal. This species has basidiomes that stain blue-green and basidiospores with crowded spines that are characteristic of the genus Octaviania. However, O. ivoryana is the only Octaviania species described from sub-Saharan Africa, and the phylogenetic relationship of the species to other species of Octaviania sensu stricto has not been previously investigated. We examined the phylogenetic position of the isotype and paratype specimens of O. ivoryana based on two nuc rDNA loci—ITS1-5.8S-ITS2 (internal transcribed spacer [ITS]) and partial 28S—and the translation elongation factor 1-α gene. The resultant phylogenies indicate that O. ivoryana does not belong to Octaviania s. s. but instead forms a clade with the epigeous bolete genus, Porphyrellus sensu stricto (i.e., P. porphyrosporus and allies). The internal transcribed spacer phylogeny also recovers a monophyletic clade that includes sequences from O. ivoryana basidiomes as well as sequences from ectomycorrhizal root tips of Uapaca, Anthonotha, and assorted ectomycorrhizal Fabaceae species, suggesting that there is likely additional undescribed diversity within the lineage. We accordingly propose a new genus, Afrocastellanoa M.E. Sm. & Orihara, to accommodate the species O. ivoryana. Afrocastellanoa is morphologically distinct from Octaviania in the combination of a solid gleba, multilayered peridium, and the lack of distinct hymenium within the gleba. Our data suggest that the genus Afrocastellanoa is a unique sequestrate lineage with one described species and several undescribed species, all of which likely form ectomycorrhizas with African trees.

KEYWORDS:

• Mycorrhiza
• sequestrate fungi
• systematics
• taxonomy

ACKNOWLEDGMENTS

The authors are grateful to James M. Trappe and Michael Castellano for facilitating access to the authentic herbarium specimens of Octaviania ivoryana and for their valuable suggestions on this study. We also thank Annemieke Verbeken for providing valuable information about the holotype of O. ivoryana. Teresa Lebel kindly sent us an herbarium specimen of Rossbeevera vittatispora. Akito Koyama and Kohei Yamamoto provided bolete specimens used for phylogenetic analyses. Mai Suyama-Watanabe helped to generate molecular data. The study was partly supported by the Grant-in-Aid from Institute for Fermentation, Osaka (IFO). Funding for M. E. Smith was provided in part by the US National Science Foundation grant DEB-1354802 and also by the University of Florida’s Institute for Food and Agricultural Sciences (IFAS).

Supplemental meterial

Supplemental data for this article can be accessed on the at www.tandfonline.com/umyc.