A synopsis of the genus Arthothelium (Arthoniales) in Tasmania

Abstract The genus Arthothelium A. Massal. in Tasmania comprises ten species. Five of these are described as new: A. bacidinum Kantvilas, a saxicolous, littoral species with subglobose apothecia, non-macrocephalic ascospores, 25−40 × 11−19 μm, and containing the pigment Endoaurantiacum-gold which yields a K+ red reaction; A. insolitum Kantvilas, lichenicolous in rainforest and characterized by subglobose apothecia, very large, non-macrocephalic ascospores, 50−80 × 22−40 μm, and containing the pigment Interveniens-brown which reacts K+ olive green; A. macounioides Kantvilas, corticolous in wet forest and characterized by sessile, convex apothecia, macrocephalic ascospores, 29−42 × 11−18 μm, and containing the pigment Endoaurantiacum-gold; A. magenteum Kantvilas, a common wet forest epiphyte with applanate apothecia, non-macrocephalic ascospores, 25−55 × 11−22 μm, and containing a unique maroon-red, K+ pink pigment; and A. subtectum Kantvilas, a saxicolous species with convex apothecia, macrocephalic ascospores, 22−36 × 9−14 μm, and containing Endoaurantiacum-gold. The New Zealand species A. endoaurantiacum Makhija & Patw. and A. suffusum (C. Knight) Müll. Arg., and the Australian A. velatium Müll. Arg. are recorded for Tasmania for the first time. The names A. obtusulum (Nyl.) Müll. Arg., A. pellucidum (C. Knight) Müll. Arg. and A. polycarpum Müll. Arg. are considered synonyms of the widespread A. ampliatum (C. Knight & Mitten) Müll. Arg. Arthothelium ferax Müll. Arg. is a synonym of A. interveniens (Nyl.) Zahlbr. and A. subspectabile Vĕzda & Kantvilas is a synonym of A. suffusum. The sole record of A. macrothecum (Fée) A. Massal. from Tasmania is found to be based on a misidentification. A key to the species is provided. The importance of apothecial pigments, apothecial morphology and ascospore septation is discussed, and three pigments are characterized by their appearance in water and other standard media.