Arctic Life/Arctic Fungi/Theres No Place Like Dung
Most major groups of fungi include some species which specialize in exploiting dung. These dung specialists, including those in the Arctic, exhibit a true ecological succession in which various fungi tend to produce spores in sequence. The zygomycetes appear first, followed by the ascomycetes, and finally the basidiomycetes. At first it was hypothesized that this succession was a nutritional one. The zygomycetes, first to appear, germinate quickly and utilize the simple sugars and hemicellulose that are readily available in dung. Once the simple sugar sources are metabolized, the zygomycetes disappear and the ascomycetes appear, feeding on the cellulose found in dung. The ascomycetes are then replaced by the basidiomycetes, which utilize cellulose and lignin. This theory seemed to fit with the observations made, but it ignored two important factors: variation in the growth and sporulation rates of different groups of fungi, and competition between dung lovers.
A second hypothesis was advanced, this time based on the time it takes for each fungus to fruit. The simple sporangiophores of the zygomycetes develop quickly and require less nutritional requirements than the fruiting bodies of the ascomycetes. Basidiomycetes require the largest amount of energy and nutrients to produce their fruiting bodies and thus they take the longest time to appear. This alternate hypothesis still neglects interspecific competition on the dung and the fact that some species of fungi act antagonistically towards others.
The succession of coprophilous fungi on dung is easy to observe. Just place some fresh or weathered dung in a sealed container with distilled water, leave it at room temperature, and watch it grow. The succession from zygomycetes through basidiomycetes should occur over three to four weeks.