THE ECOLOGY OF FUNGI

The spores and hyphal fragments of fungi are carried long distances in the atmosphere, by wind, birds and other effects.

Water habitats often abound with chytrids (water moulds). Some ascomycetes and deutermycetes also frequent both fresh and salt water. In recent years many fungi have been discovered in polluted waterways. These fungi participate in the natural decomposition of sewage. Some of these species can cause disease in humans, if eaten.

Soil is the natural habitat for saprophytic fungi, which live on organic remains. They are also a reservoir for parasitic fungi, which infect living plants and animals.

The water moulds and downy mildews are common soil inhabitants.
Certain fungi live in symbiotic association with algae, thus forming characteristic structures such as lichen. Most lichen fungi are ascomycetes, by a few species are basidiomycetes.

Fungi that is intimately associated with roots of higher plants form mycorrhiza.

This is a specialised type of hyphal growth in which part of the mycelium either wraps itself around the tips of roots, forming a velvety white cover, or it penetrates into the outer layers of the plant.

Some fungi, which ordinarily grow on dead organic matter, can infect live plants when they are given the opportunity. Others cannot exist except as parasites of living plants. The diseases caused by fungi include:

• Club-root of cabbage
• Powdery scab of potatoes
• Potato wart
• White rusts
• Potato late blight
• Downy mildews
• Chestnut blights
• Dutch elm disease
• Oak wilt
  
  

Some fungi that inhabit the soil trap microscopic organisms such as amoeba and nematodes. Most of these predacious fungi may be deutermycetes, but some might be conidial stages of basidiomycetes.

The nematodes are trapped by networks of hyphae covered with an adhesive substance, by knob shaped outgrowths that contact the prey, or by hyphal rings that swell shut abruptly after the nematodes have entered. After an amoeba or a nematode is trapped, special hyphae grow into its body. These hyphae deplete the captured body of its protoplasm.

Many small animals, insects and millipedes eat fungi. They are thus instrumental in spore distribution. Some groups of insects cultivate fungi as a food. Notable among such insects are the ambrosia beetles, tropical leaf cutting ants and certain groups of termites. However, this is not one sided, because many fungi are parasitic to insects.