L'importanza della tassonomia nel monitoraggio biologico.

Relationships between the Indice Biotico Esteso (IBE) and environmental variables are analysed and the importance of taxonomy at different levels of detail in biological monitoring is underlined. It is often observed that biotic indexes are more correlated with an upstream-downstream gradient and morphometry than with water quality. The reason may be bound to the fact that pooling taxa into larger groups both tolerant and intolerant species are included and the indicator value is lowered. It is known that species belonging to the same genus may have different ecological needs. For example considering the Diptera Chironomidae, species within the genus Eukiefferiella have different tolerance and species groups within the genus Chironomus show different response. On the contrary, taxa within the genus Microtendipes have similar tolerance and the aggregation does not alter the indicator value of the group. Thanks also to studies about different groups (Plecoptera, Ephemeroptera, Trichoptera) it can be concluded that the use of different taxonomical levels is needed to develop a good biotic index. Different indicator taxa should also be proposed for different water types. The use of larger taxonomic units such as families is discouraged, except for very preliminary surveys