Interactions between chemical and mechanical defenses in the plant genus bursera and their implications for herbivores

It is apparent that an interaction exists between the chemical and the mechanical components of the squirt gun defense in Bursera, which has resulted in some species having powerful squirts but simple chemistry. Squirting burseras tend to have more volatile chemical mixtures dominated by one or two monoterpenes while non-squirting burseras have mixtures involving sesquiterpenes and diterpenes. This interaction has had important consequences for the tactics that Blepharida beetles employ for their own defense. Blepharida feeding on squirting plants have responded evolutionarily by cutting the resin canals, which often makes them more susceptible to prédation. These beetles also compensate for their higher risk of prédation by utilizing the defensive compounds present in the plant against their own predators. Blepharida species that feed on non-squirting, chemically more complex plants do not obtain the indirect benefit of protection from their hosts and have developed an alternative behavioral defense.