Herbivory & Glucosinolates
Given the central role of spatial and temporal variation in theories of host-enemy coevolution, we established 14 long-term census populations across our study area. Naturally-occurring herbivore damage on individual plants has been censused during the growing season over a five year period. These results show ecologically and evolutionarily important levels of herbivory on Boechera, with extensive variation among sites and years. Boechera genotypes show heritable variation for insect resistance in lab and field experiments, and we have identified one of these resistance genes and quantified its effects on fitness in the field.
Arabidopsis and other Brassicaceae contain genetically polymorphic secondary compounds called glucosinolates. Generalist insects are sensitive toward glucosinolate-based plant defenses, whereas specialists can cope with these compounds, which often serve as oviposition cues and feeding stimulants. These contrasting biological effects of glucosinolates on different herbivores cause ecological tradeoffs, resulting in balancing natural selection which maintains functionally important genetic variation.