Chemical determinants of resistance in winter-dormant seedlings of European white birch (Betula pendula) to browsing by the mountain hare |
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Authors: | Jorma Tahvanainen Riitta Julkunen-Tiitto Matti Rousi Paul B Reichardt |
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Institution: | (1) Department of Biology, University of Joensuu, P. O. Box 111, SF-80101 Joensuu, Finland;(2) Punkaharju Forest Research Station, The Finnish Forest Research Institute, SF-58450 Punkaharju, Finland;(3) Department of Chemistry, University of Alaska, 99775-0520 Fairbanks, Alaska, USA |
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Abstract: | Summary A sample of one-year-old seedlings of European white birch (Betula pendula) was analyzed to determine the content of sugars, phenolics and terpenoid compounds. Two vertical segments of each seedling were analyzed separately. The number of resin droplets, which correlates strongly and negatively with feeding by the mountain hare, was also counted on the bark of experimental seedlings. The variation in the palatability of birch seedlings to mountain hare was determined primarily by the most abundant terpenoid, papyriferic acid. On the other hand, the resistance to hare feeding at the seedling bases, which are frequently attacked by voles, appeared to be dependent on other components, apparently phenolic substances. Sugars did not affect the resistance of the tested seedlings. The variation among experimental seedlings was much greater for secondary substances, especially terpenoid compounds, than for sugars. It is suggested that this high variation in protective compounds may be an adaptive trait selected for by the feeding of generalist herbivores. |
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Keywords: | chemical resistance hare browsing sugars terpenoids papyriferic acid phenolics platyphylloside Betula pendula Lepus timidus |
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