University of Michigan Biological Station

Biology 442 - Biology of Insects

Lecture Notes - Pollination

1. Coevolution Theory - main organizing theory.
   1. Definition - reciprocal changes caused by each other.1st popularized by Ehrlich and Raven 1964 with butterflies and plant families.
   2. Usually talked about in reference to herbivory but also for mutualisms - will mention later.
2. Pollination.
   1. Mutualism - rewards both participants; usually flowers get outcrossing and set seed, insects get food reward; much more efficient than wind pollination as in gymnosperms.
   2. Orders usually involved are Diptera, Hymenoptera, Lepidoptera, Coleoptera.
3. Plant adaptations
   1. Attractants.
      1. Color - UV prominent, nectar guides.
      2. Shape - radial vs. bilateral specialization associated with insects; cutting of margin.
      3. Odors - associated with appropriate pollinator; e.g. sweet for bees and butterflies, putrid for flesh flies.
   2. Deterrents.
      1. Color - red prevents many from seeing flower.
      2. Lack of reward - e.g. in wind pollinated flowers that don't want pollen eaten; flowers that fool insects with no reward.
      3. Nutrient composition - sugar for high energy insects, others need higher amino acid composition; secondary chemicals can be placed in nectar.
      4. Shape - just like above.
      5. Mechanics - some have nectar tucked away where only some insects can reach it, e.g. at end of long spur; others have way of working flower, e.g lady's slippers or iris. Some insects beat the system by nectar robbing or thieving.
   3. Orientation - similar to attractants - shape, margin cutting, nectar guides, odor source.
   4. Rewards - pollen, nectar, oils, food bodies, fragrances, brood sites, warmth.
   5. Plants getting upper hand - no reward, but fooling
4. Insect adaptations
   1. Anatomical structures
      1. Pollen carrying structures - hairs, expanded areas
      2. Nectar gathering - tongues
   2. UV abilities
   3. Learning
      1. Foraging strategies - traplining, movement patterns, pollinator constancy - bumblebees and Heinrich, pollinators influence plant population structure due to pollen flow.
      2. Energetics - study things like amount of reward, handling time, plant spacing, type of vector; competing wants of insects and plants.
   4. Insect getting upper hand - nectar robbers
   5. Pollination syndromes.
      1. Bees - sweet odor, high sugar, bilateral symmetry, UV and nectar guides, sometimes with complex mechanisms. Much slop.
      2. Flies - Open flowers that they can hover in front of, sweet, often radial symmetry, sometimes with tubes (flies with long tongues).
      3. Carrion flies - putrid odor, color of decaying flesh, often with trap mechanisms.
      4. Butterflies - open platform flowers, often with long tubes, sweet, may vary from red to UV.
      5. Moths - night fragrant, often white turning red on pollination, sweet, often with long tubes.
      6. Beetles - open flowers with lots of pollen, usually yellows to UV.
5. Other mutualisms.
   1. Seed dispersal - primarily seen in ants - myrmechory, eliasomes.
   2. Protection from herbivory in return for something - also usually with ants; extrafloral nectaries;
6. Best systems to illustrate coevolution are very specific.
   1. Yucca moth and Yucca.
   2. Fig wasps and Ficus.
   3. Ants and Acacias - system with ants living on trees, in thorns, feeding on extrafloral nectaries and food bodies; they provide protection from herbivory by other insects and mammals, fire.

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