Schizophyllum commune - nasty and sexy
Schizophyllum commune is commonly called the "Split-Gill." It looks like a a bracket (polypore) but has uniquely splitting gills. It is very common in the Australian bush, preferring to grow on burnt and dead branches of wattles and other shrubs.These small bracket-like fungi are whitish, hairy, with tough leathery flesh. They may remain dry for 50 years and when moistened will unroll their gills and begin shedding spores. Some books say you should treat them with caution, they have been linked to such adverse health effects as brain abscess, fungus ball in the lungs, sinusitis, allergic bronchopulmonary mycosis, ulcerative lesions of the hard palate, chronic lung disease, meningitis, and onychomycosis. In one case, the fungus had grown through the soft palate of a child's mouth and was actually forming mushrooms in her sinuses.
It is probably the most widespread fungus in existence, being found on every continent except Antarctica, where there is no wood to be used as a substrate. There is a single common worldwide species, although there are a few less common species of Schizophyllum. It does not appear to be very closely related to the other gilled mushrooms, and most researchers place it in its own order the Schizophyllales. The gills function to produce basidiospores on their surface. They appear to be split because they can dry out and rehydrate (and thus open and close) many times over the course of a growing season.
Unlike other mushroom species, the mycelium only has to produce one set of fruiting bodies per year, which can then dry out and rehydrate and keep functioning. It's a great strategy for reproduction.
We know that there is a single widespread species because of the work of John Raper and his colleagues at Harvard University in the 1950s-1970s. They collected worldwide samples of this fungus. After collecting and germinating the spores into mycelium, they were able to get individuals from all over the world to mate with one another. During that time they were also able to divide the species in mating types (sexes) based on their mating reactions. As long as two strains are of different mating types they are able to mate and form fertile offspring.
One of the interesting things they found is that this particular fungi has more than 28,000 sexes. It's an evoloutionary adaption to minmise the risk of mating with siblings,a nd maximise the possibility of meting with new genitic stock. Each individual is compatible with 27,997 of the others in the worldwide population (99.98% outbreeding) compared with being compatible with only 1/4 of its siblings. Thus the enormous number of sexes in fungi is meant to encourage non-sibling mating and non-relative mating, which ensures genetic diversity in the population. This seems to have worked quite well in the widely distributed Schizophyllum.