InsectPlant Interactions

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Insect-Plant Interactions

• Guest Lecture by Karla Addesso
• March 22nd

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Insects and Plantsa history

• 50 insects eat plants
• Major diversification of many insect groups
  following Angiosperm diversification (160 mya)

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What an insect gets out of it

• Food
• Pollen
• Nectar
• Foliage/other tissue
• Shelter
• Domatia
• Refugia (Enemy-Free Space)
• Oviposition sites
• Chemical compounds

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What a plant gets out of it

• Pollination
• Protection from herbivores
• Seed transport
• Food?

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The Insect Point of View
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Plants Parts to Exploit

• Flowers (buds, ovaries, pollen, nectar)
• Fruits
• Leaves (old, young, meristem)
• Stem
• Roots
• Phloem, xylem (saps)
• Storage organs (tubers, seeds)

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How do insects locate their host plant?
Taste receptors on tarsi, mouthparts, antennae
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Timing is Everything

• Bud feeding insects hatching too long after bud
  break

Bud feeding insects hatching too long before bud
break
Bud feeding insects hatching just as buds begin
to break
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Sharing Resources Niche
differentiation
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Nutrition from Plants
Insects Need Amino acids Carbohydrates Lipids,
fatty acids Vitamins Trace elements Sterols!! W
ater
Plants filled with water and cellulose
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Digesting Plant Material Aphids, Guts Buchnera

• Aphid gut removes excess water and sugar from sap
  and concentrates nutrients
• Buchnera bacterial symbionts make amino acids and
  vitamins Aphids cant
• Aphids make nutrients Buchnera cant make

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Sisterson and Gould 1999 (Ecology 80 1071-1075)
Plants as ShelterA refuge from parasitism for
Heliothis subflexa
Intact Tip removed
Melanie Bateman
7 48
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Plants as Sources of Chemicals

• Defensive compounds Danus plexippus
  (monarch)
• Pheromones
• Nuptial Gifts- Cosmosoma myrodora (Arctiidae)

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The Plant Point of View
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Insects as Pollinators

• Floral parts evolved to attract insects
• Volatile attractants
• Nectar/food rewards
• Deceptive pollination
• Nectar robbing
• free food

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Where have the honeybees gone?
A 2000 Cornell University study concluded that
the direct value of honey bee pollination to U.S.
agriculture is more than 14.6 billion.
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Insects as Plant Defenders
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Insects as Seed Transporters

• Myrmecochory
• Eat elaiosome, discard seed in nutrient rich
  dump

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Plant Rewards to Helpers
Food Bodies
Domatia
Extra Floral Nectaries
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Plant Defense Against Insect Herbivores
Defense Mechanisms
Induced
Constitutive
Tolerance
Chemical
Structural
Affect the behaviour and physiology
Insects
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Structural Defense
Trichomes
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Chemical Defense

• Phototoxins
• Cardiac glycosides (heart poisons)
• Oxidative enzymes
• Protease Inhibitors
• Lots more

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Induced Defense Call for Help

• Spider mite damage in lima bean leaves releases
  plant volatiles that attract Phytoseialus
  persimilis, a predatory mite

Perdue
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Induced Defense Talking Plants
Wild tobacco and sagebrush
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Carnivorous Plants

• Attract
• Trap
• Digest
• Absorb

Develop in areas with low nutrient soil
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Coevolution Fig Wasps and Phyllobrotica

• Wasps lay eggs in male type flowers and
  pollinate female type flowers
• 1 species of wasp per fig species
• Congruent phylogenies suggest possible coevolution

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Summary

• Many plants and insects rely on each other for
  food, defense and reproduction
• Plants must defend themselves from insect
  herbivore attack
• Insects must overcome plant nutritional
  limitations and defenses to utilize plant
  resources