In the last two decades, the interest of mycologists in multi-biont systems has increased significantly, with a large number of papers concentrating on the symbiotic relationships between algae and fungi or fungi and lichens (i.e. AHMADJIAN 8: PARACER 1987, HAWKSWORTH 1988b, POELT 1977, 1990 a, SANTESSON 1967). In addition to this, the general knowledge of fungi and lichens has grown rapidly, and many novel taxa have been described (HAWKSWORTH 1991).
Some 1000—1500 lichenized and nonlichenized ascomycetes may live on lichens. More than 250 taxa of this group are known to belong to the Lecanorales, an order in which profoUnd systematic changes are occurring. Consequently many lecanoralean lichenicolous taxa as well as their host lichens are now placed in genera, families or even suborders, different from those, where they were located previously.
For example, within the genus Lecidea in the former broad sense, there are Cases known where the systematic position of both the lichenicolous taxon and the host taxon changed, like ‘'Lecidea’ superjecta growing on 'Lecidea’ disjungenda. Both taxa hitherto regarded as members of the family Lecideaceae are now placed in the Lecanora- ceae as Carbonea superjecta and Lecanora disjungenda.
The intention of this paper is to reassess some biological aspects of multi-biont fungal-algal associations in view of the more recent results in systematics. We have concentrated our intereSt on associations between algae and two ascomycetes with special emphasis on systems where lichens are involved and where the two fungal partners are members of the order Lecanorales, the ‘inter-lecanoralean associations’, as they will be called. Some 600 constellations of this type are known.
In general it seems useful to consider multi-biont associations as multiple two-biont associations as this results a more precisely circumscribed treatment. Therefore the current usage of terminology in this field is critically reviewed. The partial associations of multiple two-biont associations are considered with particular emphasis on their biont associations are considered With particular emphasis on their efficacy. The whole range of fungal-algal associations With ascomycetes involved is elucidated and the orders involved are discussed.
As a central aspect of this paper, the multi-biont Lecanorales-Lecanorales associations are analyzed statistically. Growth form, thallus organization, biological behaviour and host specifity of the taxa involved are documentated. Data concerning the participating photobionts or substrate ecology are presented.
A revised suborder concept is used for the statistical documentation of aspects concerning the systematic of the mycobionts in inter-lecanoralean associations. The variation of several characters in the suborders under consideration is documented, e.g. some ascus characters, the types of photobionts, the sociological behaviour and some chemical aspects. The Widely distributed phenomenon of adelpho-symbiotic relationships in inter-lecanoralean associations is discussed in detail. Beside a checklist of the inter-lecanoralean associations, three supplementary checklists of several types of multi-biont associations with Lecanorales are given.