Systematics, Morphology and Ecology of Lichenized Fungi

Abstract

The general problem in systematics is the selection and evaluation of characters. Lichen taxonomy still mosuy depends on anatomical, morphological, and chemical characteristics. For example, ascus structure, spore type, and chemistry show that some species of Pertusaria are better classified within the genus Ochrolechia (Brodo 1988). Ramification patterns are used as a distinguishing characteristic in reindeer lichens (Ruoss 1989). Parasitic species of Rhizocarpon are separated into several biological types which are connected by transitions (Poelt 1990). Usually morphological observations are regarded as very reliable, but it is not always easy to be sure of the range of their variation. A formalistic use of morphology can be misleading, as could be shown in Pannaria. This genus includes species whose thallus ranges from the almost homoiomerous to the fully differentiated heteromerous state (Swinscow and Krog 1986). The development of ascocarps is examined in only a few papers. Ontogeny and structure of the apothecia of Xanthoria parietina is described in great detail (Janex-Favre and Ghaleb 1986). In the tropical lichen Auriculora byssomorpha, the ontogeny of the apothecia is characterized by a repeated formation of new hymenia within the subhymenial layer (Henssen and Titze 1990). Many papers of Henssen and her co-workers use these characters, especially in the delimination of lichens with cyanobacteria as photobiont (e. g., Henssen 1989). In another publication, it could be shown that the development and structure of the perithecia of Endocarpon pusillum is related to the genus Verrucaria, but differs from the genus Dermatocarpon (Wagner 1987).