Gynonectria intraspora gen. et sp. nov. (Hypocreales), a perianthicolous phyllosphere fungus with a novel ascospore type

Abstract

Gynonectria intraspora is described as a new monotypic genus of the Hypocreales (Ascomycetes). Relatively large perithecia form individually within the perianths of the hepatic Odontolejeunea sp. (Lejeuneaceae, Porellales), which grow in the phyllosphere of living vascular plants in the rainforests of Costa Rica and Panama. As in other hyperepiphyllous perianthicolous species, hyphae concentrate in the region of the sporophyte–gametophyte junction. They prevent sporophyte maturation, but do not visibly affect the leafy gametophyte. The most intriguing character of G. intraspora is exhibited by the ascospores. While they are still in the asci, each of them cleaves two new spores within its lumina leaving residual primary spore plasma around them. This novel spore type is comparable to the endoconidia of black meristematic fungi and is called an "intraspore". The formation of intraspores together with other features seem to indicate that the obligate hyperepiphyllous Hypocreales are undergoing an active evolutionary process of diversification, as are their epiphyllous lejeuneaceous hosts.