Lepidoptera Larvae Responses to Induced Chemical Defenses in Bilberry (Vaccinium Myrtillus) Grown in Two Climatic Conditions

Abstract

Host plant and herbivorous insect relationships are complex and intricate as they involve interactions influenced by many biotic and abiotic factors, leading to varying and often unpredictive patterns of insect populations and plant defoliation. The climate is changing and is predicted to bring higher mean temperatures globally, in addition to more frequent extreme weather, potentially affecting interactions between species and communities depending on each species unique response to the changes. If the climate affects the nutritional and chemical variations within the host plant and insect relationships, maybe this can be used to our advantage within agricultural practices, or maybe there are potential hazards. This thesis aims to gain a better understanding of this relationship by examining herbivorous lepidoptera larvae preference and performance on wild bilberry plants (Vaccinium Myrtillus) exposed to methyl jasmonate induced chemical defences and elevated temperature. Methyl jasmonate (MeJa) is a phytohormone used in signalling the defensive genetic expression in many plants. The preference and performance experiments demonstrated that the collective larvae and separated morphotypes did not react significantly to the MeJa induced defences, but rather had a significant increase in Relative Growth Rate (RGR) when eating the warmed bilberry plants compared to the larvae that were fed ambiently grown bilberry plants. This effect from warming on RGR was present from both MeJa treated and water treated plants. The slight elevation in temperature may have altered the chemical composition of the bilberry plant to become a more nutritious food for the larvae. This can alter herbivorous insect population dynamics and plant defoliation with potential economic consequences for crops and natural habitats.