ECOLOGY/EVOLUTION

Tasty Galls

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Science  01 Dec 2000:
Vol. 290, Issue 5497, pp. 1653-1655
DOI: 10.1126/science.290.5497.1653e

Many herbivorous insects are able to induce the formation of galls on their host plants. Although this ability has arisen independently in diverse insect orders during the course of evolution, its adaptive significance has remained unclear. One hypothesis is that gall-inducing insects interfere with the production of defensive chemicals by the gall tissues, rendering the gall tissues more palatable than other plant parts. Nyman and Julkunen-Tiitto investigated this possibility by studying six species of nematine sawfly gallers on their willow hosts in Lapland. In all of the interactions, they found that the sawflies reduced significantly the levels of defensive low-molecular-weight phenolic compounds in the galls. Thus, it appears that the gallers are able to redirect the biosynthetic pathways leading to these compounds; the gall and its biochemistry represent an extended phenotype of the insect. — AMS

Proc. Natl. Acad. Sci. U.S.A.97, 13184 (2000).

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