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oth as protective weapons and as potential signals. If this also holds for chemical defenses, neighbor effects might have a
_ndamental importance in shaping plant defenses. This may well be so as, because according to Provenza et al. (1992),
mmmalian herbivores learn to select food items through two interrelated systems. The affective system integrates the taste
f food and its post-ingestive consequences, while the cognitive system integrates the odor and sight of food and its taste.
tecause they have to sample plants in order to adjust food intake to avoid intoxication (Provenza et al. 1992), the expected
erbivory load of a plant is likely to depend both on its own defenses and on the defensive status of its neighbors.
SUMMARY
In order to be evolutionary stable, plant defenses should not benefit palatable neighbors too much. If they do,
_alatable plants can invade and eventually either out-compete unpalatable plants or establish polymorphic populations.
Therefore, we expect that plant defenses that can provide signals for herbivores could be superior to defenses that have no
,alue as signals. A game theoretical analysis is presented in order to explore the evolution of plant defenses when plant
]tness depends on the defensive status of the neighbor.
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