Question

This chapter presented a variety of basic plant defenses. Using any plant of your choosing, explain how it uses defenses. At a minimum, explain:

• The plant you selected and its defense mechanism;
• What kind of defense mechanism it is;
• The organism that it is defending itself from;
• How this can be used as an example of coevolution.

Answer 1

1. The selected tree is Lodgepole pine (Pinus contorta). Spines on pinecones have the potential to act as an important defense against seed predators.

2. Spines act as mechanical defence mechanism. Spines act as an anti predator defense against different species which feed on the cones.

3. The spines act as a mechanical barrier for species like Red squirrels and crossbills which can extract seeds from pinecones.

4. Pine trees have coevolved to show geographic differences in response to their seed predators. In the region where the squirrels are predominant, trees exhibit stronger defenses against squirrel predation, and in the regions where birds are the main seed predator, trees have stronger defenses against bird predation. Lodgepole pinecones are denser, contain fewer seeds, and have thinner scales to prevent the squirrels from obtaining the seeds in their area whereas, in the regions where crossbills are more prevalent, the cones are lighter and contain thick scales.