INTERSPECIFIC HERBIVORE INTERACTIONS IN A HIGH CO2 ENVIRONMENT - ROOTAND SHOOT APHIDS FEEDING ON CARDAMINE

This study investigated the effects of elevated CO2 on populations of root and/or shoot aphids and their effects on partitioning in Cardamin e pratensis. Total plant biomass in elevated (approximate to 600 ppm) CO2 of uninfested Cardamine plants was 52% higher than in ambient (app roximate to 350 ppm) concentrations but CO2 effects were not statistic ally significant. In elevated CO2, feeding by shoot aphids (Aphis faba e fabae) alone and in combination with root aphids (Pemphigus populitr ansversus), and root aphids alone had no significant effect on plant b iomass. No significant effects of elevated CO2 were detected on popula tion size of the shoot or root-feeding species. Interspecific effects were detected between the root and shoot species. Root aphid populatio ns were significantly smaller in the presence of shoot aphids on the s ame plants. In this system plant growth was unaffected by an elevated CO2 environment. Plant species which are more sensitive to elevated CO 2 may show a modified response to herbivore pressure in a future atmos pheric environment.