THE FUNCTIONAL RESOURCE OF A GALL-FORMING ADELGID

Interactions among shoots within plant modules could allow gall-insect s to acquire resources from other plant parts near the feeding sites. As a result, nearby plant parts may act as a ''functional resource'', or extended resource base. We tested for functional interconnections b etween galls and adjacent ungalled shoots in Adelges cooleyi Gil. (Hom optera: Adelgidae) on Picea engelmanni, Engelmann spruce. Observations of gall and surrounding shoot weights showed that gall weights were t wice normal shoot weights, but that surrounding shoot weights were una ffected. Reducing photosynthate availability by covering galls or surr ounding shoots with opaque cloth suggested that functional interconnec tions exist among them; covering galls reduced surrounding current-yea r ungalled shoot weight, and covering surrounding shoots reduced their weight even further, but neither covering treatment affected gall or gall-insect weight. These patterns suggest that surrounding shoots con stitute an extended and flexibly utilized resource base for adelgid ga lls. Resources made available via functional interconnections appeared to be equally available throughout adelgid galls. No differences were found in gall-insect performance in parts of the gall closer to conne ctions with surrounding shoots compared to more distantly-located gall -insects. Further studies are required to examine patterns of resource movement among unmanipulated galls and shoots. Functional resources m ay be common features of plant/gall-insect interactions, potentially p laying an important role in gall-insect reproductive success and habit at selection.