In a hypothetical study - researchers studied insect herbivory in oak forests in the Santa Monica Mountains. The researchers were interested in whether an invasive tree species, which is becoming common in the oak forests, increased herbivory on oaks. The oak trees and the invasive tree compete with one another for resources. Further, the increase in herbivory is a negative interaction for the oak. The researchers found that the invasive tree species provides cover for the herbivorous insects, which in turn are able to feed heavily on oak trees (high herbivory). This is an example of a. Apparent competition
b. Competitive exclusion
c. Mutalistic keystones
d. Indirect commentalis