Occurrence patterns of butterflies (Rhopalocera) in semi-natural pastures in southeastern Sweden

Occurrence patterns of butterflies (Rhopalocera) were analysed in relation to locality characteristics, and nested patterns were evaluated, based on a survey of 100 semi-natural pastures in the county of Östergötland, southeastern Sweden. Species richness of butterflies was positively related with locality-size, but not with the density of pastures in the surroundings. Species richness was lower in heavily grazed pastures compared with localities with a low or intermediate grazing pressure. This suggests that a uniformed, heavy grazing pressure should be avoided if butterflies are to be protected, even though such a management is favourable for many vascular plants. Out of 45 analysed species, 73% exhibited a significantly nested pattern, and species regarded to be sedentary had generally a more nested pattern. Several butterflies (such as Erynnis tages, Mellicta athalia and Pyrgus malvae) are possible to use as indicators of a relatively intact butterfly community. In a short-term perspective, the great bulk of butterflies confined to semi-natural pastures would be saved if management were adapted to the requirements of butterflies only at the localities richest in species. However, for conservation strategies to be successful over a longer time, whole landscapes harbouring the majority of the species and with a high density of semi-natural pastures should be selected and be given priority for conservation.