“Exploring how Landscape Simplification Influences Plant Defensive Strategies as Mediated by Shifts in Herbivore Populations”
As global populations continue to rise, agricultural demands have also increased. The expansion of agriculture has caused simplification of previously complex natural landscapes, which has been shown to alter the abundance and distribution of herbivorous insects. When looking at herbivorous insect damage inflicted on the wild cruciferous plant Barbarea vulgaris, the Poveda Lab found that plants from complex landscapes incurred significantly greater damage than those from simple landscapes. These differences in herbivory may play a role in selection for differing defensive strategies for wild plants in simple versus complex landscapes.
Our experiment explored how plant defensive strategies were affected by landscape mediated shifts in herbivore populations, investigating the inducibility of defensive secondary metabolites such as glucosinolates and saponins. We hypothesized that there would be greater inducibility of secondary metabolites in simple landscapes where less herbivore damage was observed and that only in more heavily affected complex landscapes, would constitutive, consistent expression of these secondary metabolites be evolutionarily beneficial.
Both a flea beetle choice bioassay and an HPLC-MS analysis were conducted for this experiment. Flea beetles showed a significant preference for plants originating from simple landscapes in the absence of induction, however, once induced, the flea beetles showed no preference. Contrary to our hypothesis, while elevated glucosinolate and saponins levels were observed upon induction, no difference in glucosinolates and saponin levels between landscape types was seen. Overall, flea beetle behavior could not be explained by differences in plant chemistry, indicating that variable glucosinolate and saponin abundance was not the main factor influencing flea beetle decisions. Next steps include investigating what else could be influencing flea beetle choice, such as physical defenses or other chemical defenses not considered here.
Participating in the Plant Genome Research Program REU through Boyce Thompson Institute and Cornell University gave me the opportunity to explore plant biology through the unique lense of agroecology and entomology. Coming from a small liberal arts undergraduate experience, the PGRP exposed me to facets of academia and research I would have otherwise not had the opportunity to explore, greatly influencing the future academic pursuits I would like to pursue in graduate school. The Poveda Lab was amazingly welcoming and provided me with an enriching environment to learn new research techniques and skills while also experiencing what high level academic research is like in an incredibly supportive environment. My summer experience was incredibly enriching and I am so very grateful to have been given the opportunity to participate!