I tested the slow-growth-high-mortality hypothesis, which states that plants, as a defense, slow the growth of herbivores to increase their exposure to the third trophic level. To test the hypothesis, I manipulated exposure of two common leaf-tying microlepidopterans (Psilocorsis quercicella and Pseudotelphusa quercinigracella) to the third trophic level on four species of oaks (Quercus alba, Q. velutina, Q. rubra, and Q. stellata). I found that plant traits differed among oak species and changed across the two generations of leaf-tiers. The two leaf-tier species experienced the first trophic level differently but were similarly affected by the third trophic level. Overall, mortality differed between generations, and leaf-tiers experienced much stronger bottom-up effects than top-down effects. Tree species identity resulted in differences in development time and pupal mass, however measured plant traits were not correlated with mortality, development time, or mass in P. quercinigracella and were inconsistent in P. quercicella. Additionally, the abundance of both leaf-tiers and predators, and pupal mass were highest on Q. alba, however this tree species had neither the highest or lowest leaf quality in terms of nitrogen availability. Overall the results from this study do not follow the predictions of the slow-growth-high-mortality hypothesis.
Often invasive plant species alter vegetative cover and modify a rodent’s sense of predation risk. Thus invasive plants have the potential to change a rodent's foraging behavior. Lonicera maackii is an aggressive and highly invasive plant that is the dominant shrub in many U.S. forested areas; in some cases the invasion changes the natural patchy understory into a massive and very dense, nearly continuous vegetation. In this study I tested the hypothesis that the invasive plant L. maackii affects the activity of Peromyscus leucopus (the white-footed mouse) by providing cover from predators and food (in the form of seeds). L. maackii cover and fruit availability were manipulated in a factorial design. The removal of L. maackii cover reduced rodent activity by 28% while fruit and seed availability had no effect on activity. This result agrees with the prediction that this invasive species alters rodent activity by providing cover, but not by providing food. Check out the final article in Oecologia