Chemical variation in the lichen genus Letrouitia (Ascomycota, Letrouitiaceae)

Abstract

he taxonomic position of the lichen genus Letrouitia Hafellner & Bellemere has been a matter of dispute. SANTESSON (1970b) included Letrouitia (as Brigantiaea p.p.) in Teloschistaceae, which he largely circumscribed by the presence of anthraquinones, even though he was well aware that anthraquinones could be found in totally different genera such as Arthonia, Biatorella, Pyrenula, Sphaerophorus and Stereocaulon. This position was unchanged (POELT 1973) until HAFELLNER & BELLEMERE (1981) described the genus Letrouitia based on ascus structure and the presence of anthraquinones. The new genus was placed in the new family Letrouitiaceae, which was affiliated with the Teloschistaceae in suborder Teloschistineae, a position it is still holding (ERIKSSON et al. 2001). The two families share the presence of anthraquinones and have rather similar, but distinct ascus types. The Letrouitia-type has a diffuse, I+ outer ascus wall, whereas the outer ascus wall of the Teloschistes-type is well-defined. The genus Letrouitia is characterised by a crustose, greenish, olive-grey to orange thallus and disciform apothecia with a mostly well-developed excipulum and a biatorine margin, which is often orange to dark brown due to crystals of anthra