Lab 4: Plant Insect Interactions: Herbivory

What are monophagous insects?

Insects that only feed on one or few closely related plant species

EG monarch butterflies and milkweed

What are oligophagous insects?

Insects that feed on several plant species belonging to the same plant family

EG Colorado Potatoes beetle with solanaceae and brassicaceae

What is a polyphagous insect?

Insects that feed on plants from multiple plant families

EG Green Peach Aphid

What is the difference between specialist and generslists for insect herbivores?

Specialists = monophagous and oligophagous

Generalists = polyphagous

What do biting-chewing mouthparts do?

Cause great mechanical damage for chewing or tearing leaf tissue

What do piercing-sucking mouthparts do?

Cause minimal damage by inserting specialized stylet in the leaf tissue to establish a feeding site

Can create specialization in the area of the plant fed on

What do rasping-sucking mouthparts do?

They cause damage by inserting a tube like stylet to lacerate cells from the leaf epidermis and suck their content

What are leaf miners?

Lepidopteran species where the caterpillar develop between the upper and lower epidermis of the leaf and feed from the parenchymal tissue

What are gall makers?

Larvae induce the formation of galls to provide protection and nourishment

How do plants recognize feeding damage?

Through cues perceived from the insect oral secretion

What is the first line of defense against insect herbivores?

Physical barriers

What is the difference between physical defenses against larger herbivores vs small?

Large = spines, thorns or urtictaing hairs

Small = chemical defenses

What is the difference between direct and indirect defenses?

Direct = directly combat herbivory; chemical secretions and physical defenses

Indirect = indirectly combat herbivory; enhance attraction of predators or parasitoids

What are some tradeoffs of plant defense?

• energy cost of producing defenses; divert energy away from reproduction and growth

• reduced competative ability

What are some examples of the secondary arms race between plants and thier insect herbivores?

• Cabbage white butterfly uses glucosinolates as feeding and oviposition clues

• Tobacco hornworms have evolves resistance mechanisms to nicotine

What is JA?

Jasmonic acid; a plant defense hormone produced in response to insect wound damage

It elicits a cascade on the activation of chemcia defnese response

What are some examples of direct defenses?

Anti-nutritive → reduce growth rate

• Nitrogen sequestration

• Protease inhibitor

Toxin → increase mortality rate

• Disease resistance protein (R)

• Polyphenol oxidase

Repellent → alters behaviour

• Glucosinolates

How do generalists tolerate plant defenses?

They use general mechanism to tolerate on array of plants defenses which means they do not master any defense and just suppress induced plant response

How do specialists tolerate plant defenses?

They gain the ability to tolerate plant defenses which means they manipulate host to their benefit and minimize the induction of high levels of secondary metabolites