The effect of the invasive Asclepias syriaca on the ground-dwelling arthropod fauna

The management of natural and seminatural systems often leads to disturbance associated with the appearance of non-native species. The spread of these species is increasing due to global environmental changes combined with local management interventions. These non-native species may establish self-sustaining populations influencing ecosystem functions, including the habitat use of native species. Here we explore the response of diplopods, spider and ant assemblages and the activity-density of individual species to the establishment of the non-native plant species, Asclepias syriaca in a disturbed poplar forest in Hungary. The relationship between the species richness of spiders and ants and the structural features of A. syriaca was weak. We found a significant relationship between the structural features of A. syriaca stands and the density and activity of the diplopod Megaphyllum unilineatum. We explain this relationship by the modified microclimate and litter quality of the habitats invaded by A. syriaca. The species composition of ant and spider assemblages was sensitive to A. syriaca. Asclepias syriaca had a negative local effect on the abundance of two spider species which were common in the studied forest. However, A. syriaca positively influenced the abundance of two ant species, most probably via indirect trophic relationships, as they feed on aphids living on A. syriaca. Our study shows that invasive plants can have mixed effects on local invertebrate assemblages. It is therefore crucial to understand how native assemblages respond to these changes in order to better manage these novel ecosystems and maximize their biodiversity benefits.