Grasshopper and butterfly local congruency in grassland remnants

Grasshoppers could be considered as appropriate ecological indicators for grasslands owing to their sensitive response to environmental features. However, if grasshoppers are a good ecological indicator, they must (i) also represent other taxa, and (ii) provide additional information over straight measurement of environmental variables. To assess this, we compared the congruence of species richness patterns of grasshoppers with butterflies and environmental variables in two areas with extensive ecological networks (ENs). ENs are landscape-scale remnants of corridors and nodes of natural habitat running throughout a transformed, usually agricultural, landscape. Species richness of grasshoppers and butterflies did not differ among reference and EN sites, but guild composition differed significantly. While ENs adequately conserved overall diversity of these two groups, they were utilized preferentially by small-sized grasshoppers and shrub and tree-feeding butterflies. Reference sites had significantly more graminivorous and intermediate-mobility grasshopper species, as well as more butterfly species with widespread distribution, herbaceous dicot feeders and those with no recorded association to forest edges. Nevertheless, grasshopper and butterfly species richness' were highly correlated. These results were similar across geographic areas, despite the fact that the areas differed significantly in their overall richness and species composition. Although there were some specific significant correlations between environmental variables and diversity, none of the variables could adequately replace use of the insect assemblage for bioindication. We conclude that grasshopper species and guild richness are representative of the butterfly assemblage, and provide information which is not sufficiently clear when utilizing only environmental variables.