Effects of Climate Change in Plant-Herbivore Interactions of an Invasive Plant
There is considerable evidence that climate change increases plant stress; however, little is understood about how it may affect plant interactions with the biotic environment. One way plant interactions may be impacted is through dynamic resource allocation within plants, which may alter plant attractiveness to herbivores. Herbivores tend to consume plants investing more in growth than defense. In plants, resource allocation is plastic, so individual plants may regulate investment between growth and defense depending on environmental stress. Plants commonly produce terpenes, a type of secondary metabolite, that often confer resistance to herbivores. Previous studies indicate that various plant species experiencing heat stress may impact metabolite expression; therefore, plants undergoing climatic stress may allocate more resources to defense, thereby deterring herbivory. Common tansy is an invasive plant common in northern Minnesota (MN). Although populations of common tansy vary substantially in both their diversity and expression of terpenes, little is known about the causes of that variation. The Moeller lab performed a transplant experiment in four regions of MN using populations of common tansy collected across MN. Each site had ambient treatments as well as temperature and precipitation manipulations to simulate climate change and evaluate how these populations may respond to climate change; preliminary chemical analyses suggest that leaf terpenes vary among tansy populations and climate treatments. To evaluate herbivore preferences for leaves collected from different populations and climate treatments, we are conducting choice tests with aphids (a common insect generalist). We are examining both insect behavior and herbivory. While we predict that aphids will prefer plants from the ambient treatment, preliminary analyses suggest that aphids generally consume more tissue from plants with lower beta-thujone (one commonly produced terpene) concentrations. This work will provide new insights into how climate change may alter plant-herbivore interactions and the geographic distribution of common tansy.