Covariation of fluctuating asymmetry, herbivory and chemistry during birch leaf expansion |
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Authors: | K Lempa J Martel J Koricheva E Haukioja V Ossipov S Ossipova K Pihlaja |
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Institution: | (1) Section of Ecology, Department of Biology, and Kevo Subarctic Research Institute, University of Turku, FIN-20014 Turku, Finland e-mail: kyolem@utu.fi Tel.: +358-2-3335722 Fax: +358-2-3336550, FI;(2) Department of Chemistry, Laboratory of Physical Chemistry, University of Turku, FIN-20014, Turku, Finland, FI |
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Abstract: | Fluctuating asymmetry (FA) is used to describe developmental instability in bilateral structures. In trees, high FA of leaves
has been assumed to indicate the level of environmental or genetic stress, and for herbivores leaves from such trees have
been shown to be in some cases (though not invariably) of higher quality compared to trees with symmetrical leaves. We demonstrated
that FA of birch leaves correlated positively with growth rate of leaves, and with the amount of leaf biomass consumed by
larvae of the geometrid Epirrita autumnata. Since asymmetry per se cannot define leaf quality for a herbivore, we determined the biochemical compounds which covary with the degree of foliage
FA, in order to elucidate relationships between leaf FA, chemistry and herbivory. High foliar FA was characteristic of birches
with high initial concentrations, and rapid seasonal decline in the concentrations of gallic acid and hydrolysable tannins,
and with rapid seasonal changes in the concentrations of flavonoid-glycosides and sugars. In contrast, leaf FA was not related
to concentrations of proanthocyanidins, protein-bound amino acids or soluble phenylalanine, the precursor of proanthocyanidins
and proteins with aromatic amino acids. The positive correlation between leaf FA and consumption by E. autumnata was presumably related to the previously demonstrated compensatory consumption of E. autumnata to high concentrations of foliar gallotannins. Furthermore, sugars are well-known feeding stimulants. We propose that the
variable results in studies correlating leaf FA and herbivory may stem from variable chemical associations of FA in different
plants and of species-specific effects of compounds on insects.
Received: 15 July 1999 / Accepted: 24 September 1999 |
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Keywords: | Fluctuating asymmetry Mountain birch Leaf growth Herbivory Foliar chemistry |
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