Illosporium Mart.
Type : * Illosporium roseum Mart. [= * Illosporium carneum Fr.]
Description : Lichenicolous. Colonies usually discrete, sometimes becoming confluent and effuse; mycelium immersed, very irregular, hyaline. Stroma, setae and hyphopodia absent. Conidiophores mononematous, forming compact convex subgelatinous sporodochia, which are often brightly coloured, very irregularly branched, and difficult to distinguish from the vegetative hyphae. Conidiogenous cells monoblastic or polyblastic, integrated, terminal or intercalary, subcylindrical to subglobose or irregular, hyaline. Conidia catenate, adhering in compact, irregular masses, hyaline singly, but usually pale-pink or rose in mass, simple, subglobose but often angular through compression by adjacent cells, smooth or indistinctly verruculose, lacking any distinct scar.
A widespread genus formerly thought to comprise four lichenicolous taxa (Vouaux 1914b: 315–318; Keissler 1930: 629–635; Hawksworth 1979a; Alstrup and Hawksworth 1990), one of which occurs in New Zealand. It is included in the Anamorphic Ascomycota (Lawrey & Diederich 2003). Hawksworth (1979a) suggested that taxa of Illosporium may in fact be members of the genus Hobsonia (see also Lowen et al. 1986), and later the genus Marchandiomyces Dieder. & D.Hawksw., established for I. corallinum (Diederich 1990). Recent molecular work on the genera Hobsonia, Illosporium and Marchandiomyces (Sikaroodi et al. 2001) attempts to clarify the situation between these three genera that have in the past been taxonomically linked. It appears from this work that Illosporium carneum is hypocrealean and probably closely related to Illosporiopsis christiansenii (Sikaroodi et al. 2001: 457), though Paul Diederich believes it to be heterogeneous. A thorough investigation of I. carneum is therefore needed to ascertain whether there may be a need to recognise additional species. At present I. carneum s. lat. is accepted as a widespread lichenicolous fungus on populations of Peltigera didactyla in New Zealand.
