LECTURE 14 CHAPTER 17 PREDATION AND HERBIVORY
Types of consumers
Herbivory
Effects on plant productivity, population size, and species composition
How demonstrates herbivory effects?
Exclosure experiments
Natural enemies hypothesis
Introduced plants escape from natural enemies population explodes
Biological control
Introduce natural enemy to control introduced plant
Herbivore selectivity
Plant deterrents to herbivory
Structural (e.g. spines; leaf toughness)
Low nutrient content in vulnerable parts
Mutualism with a predator of herbivores (e.g. ants-Acacia
Secondary chemical compounds
Herbivore growth regulators
Toxins against generalist herbivores
Digestive inhibitors against specialist herbivores
Constitutive vs. induced defense
“World is green” hypothesis
Herbivores consume low amount of plant productivity
What limits herbivory?
Top-down control from predators; tri-trophic interactions
Bottom-up control from plant defense or nutrient limitation
Abiotic factors
Intraspecific competition
Predation
Adaptations of predators
Size of prey relative to predator size
Field studies of predation: Do predators determine prey abundance?
Removal experiments
Prey deterrents to predation
Group living and early detection of predator
Induced structural defense
Chemical defense (active warfare)
Cryptic coloration (crypsis)
Aposematism (warning coloration)
Batesian mimicry: palatable species mimics unpalatable model
Mullerian mimicry: unpalatable species resemble each other