Butterflies in Portuguese 'montados': relationships between climate, land use and life-history traits

摘要

Butterfly life-history features are expected to co-vary along environmental gradients related to changes in the vegetation structure or composition; however the direction and intensity should vary across regions at the large scale. This study focuses on the butterfly communities of Portuguese 'montados'. Sixteen sites (mostly cork oak fields) were selected, reflecting a succession gradient in the vegetation of the understorey after human intervention. While controlling for vegetation and broader geographical and climate effects, we looked for trends in butterfly species richness and abundance (using generalised linear models) and for trends in species composition (using redundancy analyses). Moreover, we tried to uncover the co-variation between the butterfly life-history characteristics and succession. The results revealed that butterfly species richness was not significantly influenced by any of the considered variables. In contrast, abundance depended on geographic and oceanity-continentality gradients as it increased towards the East and with more marked temperature annual ranges and less dry summer conditions. Species composition was influenced by temperature ranges and by shrub coverage. There was no strong evidence in favour of fast-slow or generalist-specialist syndromes co-varying along human imposed environmental gradients. However, after controlling for the broad scale variables (geography and climate) shrub cover emerged as a relevant factor. This reinforces the idea that late successional stages are not optimal for butterfly communities. It implies the importance of the extensive methods of traditional management and the negative effects of long-term abandonment.