The presented examples illustrate that defense and coun-terdefense strategies of organisms are not static but all organisms are forced to adjust to changing threats from their environment. While in higher organisms these coevolutionary adaptations happen only on a large


Attack Counterdefense Altered counterdefense


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Altered defense Prey

Altered defense

Figure 9 Coevolution of defense and counterdefense strategies between predator and prey.

timescale, evolutive adaptations can be followed in case of microorganisms with their short generation cycles within a few years. A great diversity and flexibility of counter-measures against toxins or antifeedants is realized. These may range from simple solutions, for example excretion, to advanced detoxification mechanisms and finally sequestration and the use of the foreign toxins for the own defense (see Animal Defense Strategies).

The interactions between predator and prey provoke an arms race in a competition for living space and nutrition. For a specialist predator, it is advantageous to exclusively feed a specific prey that is toxic to most other organisms as this behavior releases them from competition on food and living space by others. However, extreme adaptation also bears the risk of a high dependency on a certain prey. Thus, in a fast changing environment highly specialized organisms are less flexible in switching to alternative food sources.

In conclusion, all defense mechanisms challenge a coevolutive counterdefense (see Figure 9) with both the predator and the prey having to face costs for defense and counterdefense that result in suboptimal development for both organisms but guarantee their coexistence.

See also: Animal Defense Strategies; Defense Strategies of Marine and Aquatic Organisms; Plant Defense.

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