A preliminary classification of running‐water sites in Great Britain based on macro‐invertebrate species and the prediction of community type using environmental data

SUMMARY. 1. Macro‐invertebrate species lists were obtained for 268 sites on forty‐one river systems throughout Great Britain by qualitative sampling in spring, summer and autumn. Information on twenty‐eight environmental variables was also collated for each site. The sites were ordinated on the basis of their species content using detrended correspondence analysis (DCA) and classified by two‐way indicator species analysis (TWINSPAN). Correlation coefficients between ordination scores and single environmental variables indicated that Axis 1 distinguished between types of rivers and Axis 2 reflected variation along the length of rivers. A preliminary classification of sites into sixteen groups has been proposed, together with a key which allows new sites to be classified. Information on the species and environmental features which characterize each group is also presented. 2. Multiple discriminant analysis (MDA) was employed to predict the group membership of the 268 sites using the twenty‐eight environmental variables. 76.1% of sites were classified correctly. An independent assessment of predictive ability using forty test sites yielded a 50% success rate. Predictive ability was higher for the classification presented in this paper than in fifteen additional classifications produced using data from single seasons and/or different taxonomic treatments. 3. TWINSPAN and MDA were found to be useful approaches to the classification of running‐water sites by their macro‐invertebrate fauna and the prediction of community type (as indicated by the occurrence of species in the sites comprising the group) using environmental variables. Extension of the scope of the classification, coupled with the use of additional environmental variables to increase predictive ability, is now in progress.