Coevolution: Plant–Insect

Coevolution between plants and insects is a relatively frequent phenomenon, in part because of the enormous species diversity of both groups. It is often diffuse, resulting in variability and radiation, and is presumed to result in unstable relationships. Coevolutionary relationships mainly occur between plants and herbivorous insects and between plants and pollinating insects. The mechanisms by which plants and insects interact and perceive each are very diverse, but can be broadly split into two categories: chemical and physical. Insects use a combination of chemical and physical cues to detect and discriminate plants, whereas plants manipulate both of these to either deter or attract insect visitors. These cues can be used either honestly (as warning of potential defences or to advertise offered rewards) or deceptively. Key Concepts: Plants and insects have coexisted and interacted for more than 350 million years. There is a huge diversity of plant–insect interactions; the equally vast diversity of plant and animal species is thought to be due in part to the selective pressures arising from these interactions. Mechanisms by which plant–insect interactions occur include both physical and chemical. Multiple physical and chemical mechanisms may be involved in an individual interaction. Selection has therefore occurred on multiple aspects of both plants and insects, including their morphology, biochemistry, development, sensory systems and life cycles. Plant–insect relationships are not stable; mutualisms can shift to the detriment of either of the partners. Keywords: angiosperm; arms race; coevolution; defence; herbivore; insect; mimicry; pollination