Les papallones com a bioindicadores dels hàbitats a Catalunya: l'exemple dels prats de dall i le pastures del Parc Natural dels Aiguamolls de l'Empordà

Abstract

Aiguamolls de lEmpordà Natural Park is one of the most important protected wetland areas on the Mediterranean coast. In this article, butterfly assemblages were used to characterize and evaluate the conservation value of the main habitat types in this protected area. Butterfly data were obtained from a number of transects walked as part of the Catalan Butterfly Monitoring Scheme, which uses a standardized methodology for monitoring butterflies. Hay meadows flooded in winter (the so-called closes) appeared always as the highest ranked habitat in terms of conservation evaluation: they have more butterflies and a slight tendency to harbour more and generally rarer species. This conclusion coincides with that of previous investigations indicating that the most diverse and rare plant communities in the whole Natural Park are present in the closes, and highlights the importance of traditionally managed hay meadows for wildlife. However, these hay meadows are in alarming decline and have become one of the most threatened habitats in this area and the whole Mediterranean region. In a second part of the article, we analysed the responses of butterfly communities once the closes are abandonned or when they are recovered from former arable fields. Changes may be completely overlooked if the analyses are focussed on general patterns for the whole community (e.g. species richness and abundance). On the other hand, several individual species showed strong population trends and some of them may be considered as true bioindicators of the narrow environmental conditions associated with this kind of habitat. In particular, we suggest that Plebejus argus represents an excellent bioindicator of these traditionally managed hay meadows: its populations always showed dramatic decreases once the closes were abadonned, overgrazed or invaded by exotic weeds, and progressive increases once the quality of the meadows improved. Moreover, this highly sedentary species exists as metapopulations and, therefore, the wealth of local populations also reflects that of the surrounding landscape.