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

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.