Predator-Prey Interactions. We wish to know: how predators affect prey populations, and vice-versa what stabilizes predator-prey interactions and prevents their collapse how predation can result in complex interactions in natural communities. Consumer-Resource Interactions. Predation
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In simple environments, Paramecium either is eliminated by a protozoan predator, or the predator fails to find enough prey and dies out.
In more complex environments, with refugia for the prey or when prey are allowed to “immigrate” into the system, predator-prey cycles persist for some time.
Lynx and Snowshoe Hare
Annual fur trapping records demonstrate a 10-year cycle in prey and predator abundance.
Densities per area of orange for the prey mite Eotetranychus and the predator mite Typhlodromus, provided with 20 small areas of food for the prey alternating with 20 foodless positions.
One predator-prey cycle is completed before predators eliminate the prey.
Four cycles are obtained over ~ 60 weeks in a complex laboratory environment consisting of 252 oranges, with 1/20th of each orange exposed, and barriers to dispersal.
Fluctuations in abundance of the azuki bean weavil and its larval parasite (a wasp) in a laboratory setting.
Note the similarity to a predator-prey cycle.
In simple lab systems, predators often extinguish their prey and then starve. Why doesn’t this occur in nature?
Plant Defenses Environment
Cactus- Sharp spines may pierce and cause allergic reactions
Tobacco- Production of toxic secondary compound (nicotine)
Pitcher Plant- Leaves secrete nectar to attract insects to eat
Magnolia Leaves- Tough, waxy covering
Logically, the lynx cycle should lag behind the hare cycle, especially if the predator controls the prey. On occasion, the lynx appears to be “ahead” of the hare.