Associational resistance

This type of commensalism involves one species produces a compound that another species used to help fend off predation or herbivory. This is commonly found in plants.

For example, the chrysomelid beetle is an herbivore to the purple loosestrife plant. When this plant is growing in an area by itself, the beetle causes quite a bit of damage. However, when the purple loosestrife finds itself living amongst Myrica gale, an aromatic shrub, the beetle does less damage. This observation is due to the shrub produces volatile chemicals from its roots and leaves that deter insects from eating it. Because of this shrub reducing beetle numbers, the loosestrife plant benefits greatly and no extra cost to the shrub.

Answer question 33 on your handout.