Chlorostroma vestlandicum sp. nov., a host-specific mycoparasite on Hypoxylon vogesiacum from western Norway

Abstract

The new species Chlorostroma vestlandicum is described from coarse dead wood of Ulmus glabra in western Norway. It was invariably found in close association with Hypoxylon vogesiacum and appears to be mycoparasitic on this species. With a strikingly orange entostroma, tiny perithecia and specialized habitat association it is a highly distinctive species. C. vestlandicum differs from the type species by the color of the entostroma (bright yellow orange as opposed to ochraceous), iodine reaction of the apical apparatus, ascospores (more or less ellipsoid as opposed to more or less cuboid). The surface is not green or bluegreen as in the previously described species, albeit dark greenish blackish in section. Its distribution seems to cover mainly the hemiboreal regions of western Norway, an area not yet affected but threatened by Dutch elm disease. It is probably a rare species restricted to the most dead wood rich sites with big populations of H. vogesiacum.