Invertebrate diversity found on common milkweed (Asclepias syriaca) during Wisconsin growing season

Abstract

Common milkweed (Asclepias syriaca) is studied for its defense mechanisms and species interactions. It is a host to a variety of species throughout the growing season, with distinct species attracted to various parts of the plant. I observed both established and first year plants from May through September 2017, to determine the diversity of the invertebrate community found on the milkweed throughout the growing season. The information was broken into months, then analyzed to determine species richness and any overall trends. I identified 22 species from ten taxonomic groups. The highest species richness occurred in July and August. The most common groups of insects were aphids and weevils, which were observed in 11 out of 12 time periods. I observed that the invertebrates stayed mainly on the established milkweed until the first-year plants had grown larger. A positive correlation of r = 0.78 between height and species richness supports this. I also found a positive correlation between average species richness and percentage of leaves with chewing damage (0.27). This information could help with further research on how insect populations interact with and affect milkweed and when protection, such as insecticide, should be applied.