ECOLOGY/EVOLUTION

Leaf Signals

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Science  19 Sep 2003:
Vol. 301, Issue 5640, pp. 1631
DOI: 10.1126/science.301.5640.1631a

There are many potential explanations for the adaptive significance of autumn colors in the senescing leaves of temperate deciduous trees. One idea is that coloration is a signal to insects about the tree's investment in chemical defenses against herbivore attack. Hagen et al. investigated this possibility over three growing seasons in mountain birch trees in northern Norway. The degree of autumn coloration in September was negatively correlated with the amount of insect damage to the following season's leaf crop, and with physiological indices of stress and reproductive investment. The commonest leaf-chewing insects in the study area are geometrid moths that lay their eggs in the autumn. Though the causal link is yet to be established, the results are consistent with the hypothesis that the insects prefer less discolored leaves. — AMS

Ecol. Lett. 6, 807 (2003).

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