Additive genetic variation of secondary and primary metabolites in mountain birch

Evolutionary adaptations require genetic variation in the traits concerned. Mountain birch populations suffer from regular autumnal moth defoliations that affect tree survival and growth. Earlier studies have found that birch individuals show clear differences in their leaf chemistry, which may be relevant to herbivore performance. A large part of this variation is assumed to be genetic, since quantitative differences between trees remain the same in different years. We estimated the genetic parameters of several herbivory-related chemical compounds. The material consisted of 30 mature wild trees and their progenies. We treated the data both as half-sib and full-sib families, and calculated parent-offspring comparisons as well. The compounds included 12 individual phenolics, 5 carbohydrates and 16 protein-bound amino acids. For comparison, we also analysed the weight and germination percent of seeds and the height of seedlings. Two of the most abundant phenylpropanoids (chlorogenic acid and kaempferol-3-O-α-L-rhamnopyranoside) showed significant genetic variation, but this was not true of all individual phenolic compounds. Amino acids had less genetic variation than phenolic compounds. The high genetic variation of the phenolic compounds indicates that the mountain birch is able to evolve its phenol-based resistance.