Morphology and Phylogeny of Ascomycete Lichens

Abstract

A wide range of taxa in the higher ascomycetes (Pezizomycotina sensu Eriksson and Winka 1997) forms some sort of symbiosis with algae and cyanobacteria. These associations include fungal parasites on algae (Hawksworth 1987; Lewin 1995), mycophycobioses (Kohlmeyer 1967; Kohlmeyer and Kohlmeyer 1972), lichenicolous fungi (Hawksworth 1983, 1988a; Clauzade et al. 1989) and lichens (Nash 1996). Naturally, the delimitation of these associations is not clear and intermediate forms exist. However, an attempt to define these terms is made in Table 1, following Hawksworth (1988a). An exhaustive treatment on fungal-algal associations in the large order Lecanorales can be found in Rambold and Triebel (1992). This chapter concentrates on the morphology, phylogeny and classification of lichen-forming ascomycetes. Only a brief treatment can be given here and the reader is referred to other recent books for more information (e.g., Ahmadjian 1993; Nash 1996).