The relationship between butterflies and environmental indicator values: a tool for conservation in a changing landscape

Abstract

We examined relationships between Dutch butterfly species and the Ellenberg indicator values for nutrients, acidity and moisture. Presence/absence data on butterflies were obtained from monitoring transects of the Dutch Butterfly Monitoring Scheme. Mean indicator values were calculated from vegetation samples of a selection of transect sections. Single and multiple logistic regression models were used to analyse the relationships. Except for the moisture value, the vegetation samples covered the Ellenberg scales quite well. Significant correlations between moisture and acidity (−) and nutrients and acidity (+) were observed. Sites that were both acid and nutrient-rich were not observed. Most of the observed significant relationships were unimodal (Gaussian), in which species show a clear optimum indicator value. Other species showed a sigmoidal (linear) response to one or more of the ecological indicator values. Several species were significantly correlated with all three indicator values. For a small group this was also the case in the multiple regression model. This was probably caused by multicollinearity of the indicator values, leading to some spurious significant single regression models. We discuss methodical problems and possibilities for refinements of the models. The observed relationships between butterflies and indicator values agreed well with available ecological information.The observed regression models can be used to (a) predict the effects of environmental factors on the butterfly fauna, (b) use changes in the abundances of certain species as indicators of ecological processes and (c) determine the sensitivity of butterflies for eutrophication, acidification and ground-water draining. In conclusion, the models provide a powerful aid in the conservation of butterflies in a changing environment.