Linear scaling – negative effects of invasive Spiraea tomentosa (Rosaceae) on wetland plants and pollinator communities

Invasive plants directly and indirectly disrupt the ecosystem functioning, of which indirect effects, for example, through trophic cascades, are particularly difficult to predict. It is frequently assumed that impact an invading species on proportional (linearly related) its density or abundance in a habitat, but this assumption has rarely been tested. We hypothesised richness potentially pollinators wet meadows change as result invasion steeplebush Spiraea tomentosa these changes shrub. selected 27 sites amongst habitats invaded by S. with coverage ranging from 0% 100% examined diversity plants, well flower visitors (bees, butterflies moths flies). Our results showed number individuals visitors, decrease significantly linearly increase cover. This finding supports hypothesis invasive can be their population density, especially if limiting available resources without supplying others. study first show such unequivocal negative, linear effect shrub potential pollinators. proves negative wetland appears even minor invader, should taken into account when planning activities aimed at controlling transformer species. The simultaneously detected dependence allows us assume benefits secondary populations incurred effort.