Interspecific competition in ant species and change in C:N of plants following the transfer of aphids to common milkweed.

Abstract

Ant-aphid mutualism is seen among many species of plants and throughout the world however only two species of aphids specialize on the common milkweed (Asclepias syriaca). For the purpose of this study we focused on the relationship between green aphids (Aphis asclepiadis), several ant species, and milkweed at The University of Michigan Biological Station. We observed the ants and aphids on 20 different milkweeds for four days and recorded any interspecific competition between ants over novel aphids. Additionally we analyzed plant chemistry before the transfer of aphids on the original and novel plants, also, after the transfer and tending of aphids on the novel plant. In order to find the effect of ant-aphid mutualism on the plant’s C:N and to find an underlying difference for the presence or absence of aphids we ran plant chemistry. This experiment found no significant differences in interspecific competition or plant chemistry. Although we found no significant differences in plant chemistry we did find that plants with aphids and plants with the mutualism had a smaller increase in Nitrogen than the plants with no aphids present. Our experiment could be applied to an agricultural setting to measure the effects of pests, such as aphids, on the change in C:N of plants; in other words monitor the effect of aphids on plant growth.