Original paper

Rare and common macroinvertebrates: definition of distribution classes and their boundaries

Nijboer, Rebi C.; Verdonschot, Piet F.M.


Rarity of macroinvertebrates can be used in assessing the ecological quality or conservation value of freshwaters. To select target species for nature conservation and to compare rarity or commonness between regions a classification of species distributions is needed. A distribution classification for Dutch macroinvertebrate taxa is presented. Frequencies of occurrence in surface waters of aquatic macroinvertebrate taxa were extracted from databases of water district managers and included data from 7608 sites from 1980 to 1998. Six classes were defined: very rare, rare, uncommon, common, very common, and abundant. The boundaries for these classes were established using the number of occurrences of the taxa and the expert opinion of a committee of water district managers and taxonomic experts. A distribution class was assigned to each of 1544 taxa, including 1514 species and 30 taxa on higher taxonomic level (groups, aggregates, genera). There were still many taxa for which the distribution was unknown due to their small size, their special habitat requirements, or identification difficulties due to immature animals and incomplete taxonomic information. The number of rare species differed between the 24 water management districts and depended on characteristics of the area, sampling strategy, and sampling intensity. The percentage of rare species differed between taxonomic groups. The definition of distribution classes and their boundaries can be applied at different scales, (e. g., water management district or national scale), which makes results comparable between scales and provides a broad application in bioassessment and conservation.


distribution classificationraritymacroinvertebratesspecies conservationred data book