## Estimation of Population Size

Databases often show how many localities a species is known from, but give no clues on the number of localities which host the species. To estimate the actual number of individuals in a region, it is necessary to have an idea of the magnitude of yet unknown localities of each species in question and of the number of mycelia in each locality. A possible way of estimating this is to multiply the known number of localities by a factor representing the likely proportion of undiscovered localities for the species (locality factor) and by a factor representing the likely number of mycelia per locality (mycelium factor). When a species is very conspicuous, fruits every year, has very exact ecological demands and occurs in a well-investigated biotope, these factors may be very low, and the estimated total number may be close to the actual number of mycelia. An example of such a species could be the conspicuous orange polypore Hapalopilus croceus, which is restricted to very old oaks. Inconspicuous species that are not well investigated may, on the other hand, be assumed to have large locality and mycelium factors giving a high estimated total number of mycelia, even when the known number of localities is small.

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