ecopredation2 by AYizsq



Great White Shark and Fur Seal

    Arctic Ground Squirrel –
Predator population is self-limited
    Red Grouse in Heather –
Predator population is self-limited
  Predator Switching Regulates Prey Population

                                  Bank vole

Tawny Owl
Cinnabar Moth and Caterpillar on
        Ragwort Tansy
Snowshoe hare and Lynx

Ruffed Grouse   Snowshoe hare
Sea Otter
Sea Urchin
Sea Otter eating Sea Urchin
      in Kelp Forest
Comparison of kelp and urchin biomass with and
              without sea otters
Kelp forest ecsystems with and without
               sea otters
Sea Urchin Barren
           Plant Resource Defense

• Qualitative defense - highly toxic substances,
  small doses of which can kill predators
• high nutrient environment/fast growth (high
  turnover in plants) - use toxins (plant
  secondary compounds) that often require N,
  expensive to make (must be replaced often),
  but can be made rapidly - cyanide compounds,
  cardiac glycosides, alkaloids - small molecules
          Plant Resource Defense
• Quantitative defense - substances that
  gradually build up inside an herbivore as it eats
  and prevent digestion of food
• low nutrient environment/slow growth (low
  turnover in plants) - primarily use carbon
  structures - wood, cellulose, lignin, tannins -
  large molecules - makes plant hard or
  unpleasant to eat (woodiness, silica), but plants
  are slow to make these defenses
Evolutionary “Arms” Races

      Monarch and milkweed
Evolutionary “Arms” Races
         Evolutionary “Arms” Races

California garter snake   Pacific newt
        Other Plant Defenses Include:
• mechanical defenses - plant thorns and spines deter
  many vertebrate herbivores, but may not help much
  against invertebrate herbivores
• failure to attract predators - plants somehow avoid
  making chemicals which attract predators
• reproductive inhibition - some plants such as firs
  (Abies) have insect hormone derivatives which if
  digested, prevent successful metamorphosis of insect
• masting - the synchronous production of very large
  numbers of progeny (seeds) by trees of one species in
  certain years
Eurasian Jay with Acorn
Fagus sylvaticus – European Beech
Dipterocarp distribution
Dipterocarp trees
Beech seeds and boring moth
Masting and Human Health
    - Lyme’s Disease
             Induced Defenses
• Another aspect of plant defenses is that plants
  do not always have tissues loaded with
  defensive chemicals - in many plants,
  defensive chemicals are only produced when
  they are needed, usually after the plant has
  experienced some herbivory - this is an
  induced defense
Impact of Herbivores Is Not
  Uniformly Experienced
Aphids attacking Alfalfa

                Spotted Alfalfa Aphid
Rubus prickles
Acacia depanolobium
 Plant defenses are developed at a cost
            to fitness when:
1. Organisms evolve more defenses if they are exposed
  to much damage and fewer defenses if cost of defense
  is high
2. More defenses are allocated within an organism to
  valuable tissues that are at risk
3. Defense mechanisms are reduced when enemies are
  absent and increased when plants are attacked -
  mostly true for chemicals not structures
4. Defense mechanisms are costly and cannot be
  maintained if plants are severely stressed by
  environmental factors
Serengeti Grazing System
Serengeti Grazing System
Opuntia stricta – prickly pear
Prickly Pear
Infestation in
Area infested with prickly pear before biocontrol
Same area infested with prickly pear after biocontrol
Biocontrol Agent – Cactoblastis cactorum

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