Flora of New Zealand Series

Type : * Biatoropsis usnearum Räsänen

Description : Basidiomata variable in form and colour, cartilaginous; context hyphae without clamp connections; haustorial branches tremelloid. Hymenium containing numerous basidia; probasidial initials clavate; hyphidia and cystidia absent. Basidia, when mature, clavate to subcylindrical, transversely septate; epibasidia subcylindrical. Basidiospores subglobose to ellipsoidal, with a distinct apiculus, germinating with a germ tube. Anamorph hyphomycetous : catenate conidia are common.

Biatoropsis is a widely distributed monospecific genus, forming pinkish galls on species of Usnea. Misunderstood for many years as an ascomycete and earlier referred to Abrothallus parmeliarum, the true nature of Biatoropsis as a heterobasidomycete with auriculoid, transversely septate basidia was shown by Diederich & Christiansen (1994), who give a detailed taxonomic history of this gall-forming fungus. The systematic position of the genus is unclear and at present it is included within the Basidiomycota in Tremellales incertae sedis (Lawrey & Diederich 2003; Pennycook & Galloway 2004). The sole species, B. usnearum, forms galls on at least 52 species of Usnea and also on Protousnea dusenii. An account of the structure and devlopment of the galls in B. usnearum is provided by Grube & de los Ríos (2001). B. usnearum does not occur on species of Neuropogon, and this argues for the recognition of Neuropogon as a separate genus and also for Protousnea to be regarded as a subgenus of Usnea (Diederich 1996: 186). The following species of Usnea occurring in New Zealand are known hosts for B. usnearum : Usnea angulata, U. inermis, U. molliuscula, U. nidifica, U. oncodes, U. rubicunda, U. torulosa and U. xanthopoga (Diederich & Christiansen 1994: 49–51). Galls of Biatoropsis have been found parasitised by * Abrothallus usneae and three species of * Lichenoconium viz., * L. erodens, * L. lecanorae and * L. usneae (Diederich & Christiansen 1994), and these should be looked for in New Zealand material. It is widespread but still very poorly collected in New Zealand.