Introduction

Abstract

Fungi are heterotrophs, and because of this, they play several distinctive roles in ecosystems: as saprotrophs, as parasites of plants and animals, as mutualistic symbionts of many phototrophic organisms, e.g. cyanobacteria and algae in the form of lichens, and as mycorrhizal partners of vascular plants. Indeed the earliest vascular plants had mycorrhizal associations, and it has been claimed that mycorrhizal infection was the key to successful colonization of the land (Pirozynski and Malloch, 1975; Pirozynski and Hawksworth, 1988; Pirozynski and Dalpé, 1989.