Indirect effects of earthworms (Aporrectodea caliginosa) on an above-ground tritrophic interaction

Effects of earthworms in soils of contrasting nitrogen content on a plant-aphid-parasitoid interaction were investigated in a greenhouse experiment. Presence of earthworms (Aporrectodea caliginosa) increased root biomass and carbon content of shoots of Cardamine hirsuta. The nitrogen content of shoots and roots was increased by earthworms, but only in the more enriched nutrient soil. Aphid reproduction (Myzus persicae) was enhanced by the presence of earthworms. Soil type, but not earthworm presence, affected the dynamics of the parasitoid wasp Aphidius colemani, the number of parasitised aphids was increased on plants growing in the enriched soil. Larger parasitoids also emerged from mummies of plants growing in this soil.