Low nutritive quality as defense against herbivores

Contrary to a widespread assumption in the literature on plant-herbivore interactions, individual plants do not necessarily benefit by possessing traits which lower herbivore fitness. In particular, genes conferring lowered nutritive quality could even increase herbivore damage under certain circumstances. Three special sets of conditions are outlined in which low nutritive quality would lower herbivore-induced damage to an individual plant. These sets are far from exhaustive. It is concluded that the adaptive-ness of lowered nutritive quality in herbivore defense is widely possible but in no case demonstrated. Discussions of plant-herbivore interactions often assume that plant traits are favored by natural selection to the extent that they lower herbivore fitness (e.g. Rhoades, 1979; Feeny, 1976; Rhoades & Cates, 1976). Thus, Feeny (1975, p. 4) claims that:... plants... may use for protection substances of relatively subtle effect; these may not even be immediately toxic to an invading insect individual but neverthe-less can reduce its fitness. This serves the function both of minimizing a populatio