Effects of larval age and prolonged simulated acid rain on the susceptibility of European pine sawfly to virus infection

Effects of pollutants on bottom-up and top-down processes in insect-plant interactions

Bottom-up (host plant quality) and top-down (natural enemies) forces both influence the fitness and population dynamics of herbivores. However, the impact of pollutants acting on these forces has not been examined, which prompted us to review the literature to test hypotheses regarding this area of research. A comprehensive literature search found 126 references which examined fitness components and population dynamics of 203 insect herbivores. One hundred and fifty-three of the 203 herbivores (75.4%) had fitness impacted due to bottom-up factors in polluted environments. In contrast, only 20 of the 203 (9.9%) had fitness significantly impacted due to top-down factors in polluted environments. The paucity of results for top-down factors impacting fitness does not necessarily mean that top-down factors are less important, but rather that fewer studies include natural enemies. We provide a synthesis of available data by pollution type and herbivore guild, and suggest future research to address this issue.

Direct effects of heavy metal pollution on the immune function of a geometrid moth, Epirrita autumnata

Previously, we found that Epirrita autumnata larvae, which were fed with leaves that came from a metal polluted area, had an enhanced immune function. To investigate further the cause of the enhanced immunity we examined experimentally the direct influence of the heavy metals, copper and nickel, on the immune function of the geometrid moth we artificially added the metals to the surface of birch leaves to examine their direct effects. As a measurement of the strength of immune function, we used encapsulation rate against a nylon monofilament. A moderate amount of Ni and Cu in the diet of moth larvae increased their encapsulation rate, but a large amount of Cu caused the immune function to decrease. The results indicate that Ni and Cu have direct effects on immunity. Moderate amounts of those metals increase immune function, but large amounts lead to inhibition of immune function.