Connecting the dots: How microbiomes can help understand plant-insect interactions

How plants respond to herbivory is shaped by several factors, such as plant genetic composition, herbivore species, and associations with microorganisms. Plants are generally thought to have evolved means to perceive and withstand attack from generalists and specialist herbivores, while also developing mutualistic relationships with microorganisms to acquire nutrients and other growth promoting factors. When plants are fed upon by herbivores, mutualistic relationships with microorganisms can change due to shift in resource allocation patterns. In invasive plant systems, plants establish in new locations and form associations with local microbiomes that are distinct from native ranges. When biological control agents are introduced to the new range, they interact with plants that have distinct associations and can have different responses to herbivory. Microbiome composition between native and introduced ranges have been widely studied and generally have proved to be distinct. However, how such differences impact plant response to herbivory is still understudied. Using the invasive plant Russian knapweed (Rhaponticum repens) as a study system, I sampled rhizosphere, root, and aboveground microbiomes across sites that experienced different levels of herbivory. Bacterial (16S) and fungal (ITS) amplicon regions were sequenced to study microbial diversity and composition in six sites across Colorado. Bacterial and fungal compositions changed according to site and insect establishment within each sample type. Results of these studies will help enlighten effects of microbiomes on plant-insect interactions and how such interactions impact the success of biological control programs.