Fungi move mainly by growing. The cells in fungal hyphae divide and grow and this stretches the hyphal threads out into the soil or whatever substrates the fungi are using. This is a good strategy for reaching nearby food sources but for long distance dispersal, other methods are needed.
The mushrooms we see popping their heads up out of the soil are the sexual organs of the fungi. For months or years, the fungus has been growing and feeding unnoticed under the ground. At last, the fungal hyphae join together to form the mushroom. The purpose is two-fold: sexual recombination of genes to promote diversity and dispersal of those sexual spores to new habitats.
There are two major groups of mushroom-producing fungi: the ascomycetes and the basidiomycetes. Ascomycetes produce their round spores in microscopic cells called asci. The asci hold the spores and protect them from the air. One ascus typically holds eight spores but this can vary between species from one to a hundred spores. Cup fungi are ascomycetes as are flask fungi. Typically ascomycetes depend on passive wind dispersal or dispersal of their spores by animal vectors that either eat them and then defecate them out in new habitats or carry them on their legs. There are more species of ascomycetes in the world but the greatest diversity of forms is found in the basidiomycetes.
Basidiomycetes have projections from cells called basidia where the spores are attached. Typical field mushrooms are basidiomycetes. These mushrooms have v-shaped gills formed by fungal hyphae with the basidia attached to them. The spores attached to the basidia are exposed to the air.
Boletes, with spongy undersurfaces instead of gills, are also basidiomycetes. So are bracket fungi, whose hyphae live in woody tissues of trees and then come together to form brackets on the surfaces of their hosts. The soft-bodied and often colourful coral and jelly fungi are also basidiomycetes as are the stinkhorms and puffballs.
Some fungi make more of an effort to spread their spores. Puffballs or gasteromycetes squirt them up in the air where the wind can catch them and move them about.
Truffle-like fungi, which form their fruiting bodies underground, can be either ascomycetes or basidiomycetes. They seem to have given up on dispersal and concentrated on sexual reproduction. Or perhaps they are simply depending on animals to find them, eat them and then defecate the spores in new habitats.
Many basidiomycetes have a unique discharge mechanism that utilises first sugar and then water to create a force to throw the spore away from the parent body. The spore is attached to the tip of the basidium by a little tail called an apiculus. When the spore is mature, it secretes a drop of sugar onto the apiculus, which gradually swells with water from the surrounding atmosphere. The drop of sugar-water swells until it touches the film of water surrounding the spore. When it breaks the energy shoots the spore out into the world with a force greater than a rocket ship, estimated at 25,000 times the force of gravity. From there, air currents waft the tiny spore away from its parent mushroom and hopefully to greener pastures. It appears that the shape of the mushroom cap is designed to cause air turbulence to help move the spores even further. Spores shot out like this are called ballistospores. Boletes, jelly and coral fungi all use ballistospore technology, while stinkhorns and truffle like fungi rely on more passive spore release methods.
Ink cap mushrooms have a slightly different solution to the spore dispersal problem. Their gills are parallel rather than V-shaped which makes it more difficult to get rid of the spores. The spores at the bottom mature first and are shot away by sugar water solution. Then the ink cap begins to dissolve and drip away. As the ink cap dissolves, the higher spores in turn mature and can be shot away as they are exposed to the air.
Insects and other arthropods such as mites are also important as vectors of fungal dispersal. Mites, crawling about over the ground and over mushrooms, pick up spores and carry them away. Insects too can land on fungi, pick up spores and carry them to new habitats. This is passive dispersal as far as the fungus is concerned. No effort is needed on the part of the mushroom to attach the spore to the vector.
A few fungal spores are actually mobile, with the use of a tail-like flagellum. These are found in water and use the flagellum to move themselves through the water to a new host or habitat.
Many parasitic fungi are spread by air currents. Asperigillosis in birds is caused by spores in the air that are taken up into the lungs of the unfortunate birds as they breathe.
Fungi are a highly successful group of organisms. They have colonised many habitats and their strategies for dispersal assist them to do this.
References: http://www.anbg.gov.au/fungi
