Presently, there are a handful of earthworms that have been recognized as invasive species in the Northeastern United States.  Given their role as ecosystem engineers, earthworms can have a profound effect on the physical environment of the forest floor.  What is no consistent is how this engineering effect influences plant species.  With the observation that Arisaema triphyllum (a rare native plant) increases abundance in the presence of earthworms, a study to examine the physiological effects on this plant was undertaken.  Compositional analysis of corms reveals significantly increased levels of nitrate and oxalic acid in plants grown in the presence of earthworms.  This suggests that earthworm presence may result in an advantage from a physiological standpoint, as well as a defensive one.