The fungi may be grouped into various ecological groups. Some main ecological groups are as follows:
1. Soil Fungi:
Along with other microorganisms fungi are also associated with microbiological phenomena in the soil. When the plants grow in the soil their roots are added to the soil system. The greatest microbiological activity remains confined to the surface of the roots, called the rhizoplane soil nearer the roots, under the influence of the exudations of the roots, is called the rhizosphere.
The fungal flora of the rhizoplane and rhizosphere play an important role in the incidence of root- disease fungi. In many cases the roots of resistant varieties of plants have been found to produce hydrocyanic acid which is however, not produced in the susceptible varieties. It is presumed that this acid has an inverse effect on the pathogenic fungi by preventing them from flourishing near the roots.
2. Lignicolous Fungi:
Lignin is quite resistant to the attack of fungi and other microorganisms. However, certain specific fungi (mostly higher fungi) are responsible for bringing about its distribution. The wood of trees is decayed by such fungi. For example Polystictus sanguinens causes the wood decay of the logs of Shorea robusta (sal tree).
3. Entomogenous Fungi:
The fungi associated with insects are known as entomogenous fungi. The most important example of this type is Entomophthora muscae on house fly. Flies attached by this fungus are generally seen in moist weather attached to glass window panes surrounded by a white halo about 2 cm. in diameter formed by the discharged conidia.
4. Coprophilous Fungi:
A number of fungi are coprophilous (Gr. kopros = dung; philein = to love), which grow only on the dung of certain animals. Hesseltine and his associates (1952) found in dung a factor which was necessary for the growth of Pilobolus. They named this factor coprogen. The dung of herbivores (e.g., horses, pigs, camels, elephants, mice, rabbits, hare, etc.) harbours a large number of fungi out of which a few are exclusively coprophilous. Usually, on dung the fruiting bodies of lower fungi (mostly Mucorales) appear first, they are succeeded by the fructifications of the higher fungi (first of Ascomycetes and later on of Basidiomycetes).
5. Aquatic Fungi:
Several fungi are water inhabiting, and are called the aquatic fungi. Several members of Chytridiales are found on algae and water molds. The Blastocladiales are chiefly water molds. Most species of Monoblepharidales are aquatic. The Lagenidiales is a small group of aquatic fungi parasitic on algae, water molds, small animals and other forms of aquatic or semi-aquatic life. Though the members of aquatic fungi are found in all fungal groups yet most of them belong to lower fungi.