NUTRITIONAL QUALITY AS A DEFENSE AGAINST HERBIVORES

The generally low nutritional quality of plants may result from its being a defense against herbivores, an adaptation to abiotic factors, or an incidental by-product. To demonstrate the defensive nature, we should be able to show that there is variation, fitness differences and a hereditary basis. We demonstrate that, in the mountain birch (Betula pubescens ssp. tortuosa), the low nutritional quality is a potential active defense against herbivorous insects, especially if it correlates with repellency caused by allelochemicals. However, it is almost impossible to show this conclusively.