The indication weight is usually given by a range of values from 1 to 5 representing the niche width and expressing the increasing stenoeciousness (i.e., increasingly narrow habitat range) of the taxon. The indication weight is derived from the way the ten points of the ten-point scale are distributed within the individual classes of saprobity. For instance, if all the ten points belong to only one class, or if nine points belong to one class and one point to another class, the taxon is classified as a very good indicator and its indication weight is 5. If the distribution of points is, say, 5:5, 6:4, or 2:6:2, the indication weight is 3, meaning that the taxon is a moderate or transitory indicator. The worst indicators with point distribution, such as 1:3:3:3, 1:2:3:2:2, and so on, have an indication weight equal to 1. Such a low value of this parameter decreases the importance of the taxon in the final calculation of the saprobic index.
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