PARENT SESSION
Poster Session #2: Plant-Animal Interactions.
Monday, August 6, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

Good things (and death) come to those who wait: Host phenology & a gall-forming aphid.

Schultz, Jack¹, Rehill, Brian ¹, ¹

ABSTRACT- We studied the synchronization and roles of host and insect phenology for fundatrices of the gall-forming aphid, Hormaphis hamamelidis. We found wide variation in host and insect phenologies among years and individual host trees. Most winter eggs (ca. 85%) hatched before bud break and galls could be initiated, but in two studies there was no inherent risk for earlier hatching fundatrices in terms of greater mortality. Egg hatch was not tightly synchronized with host trees, but instead seemed to occur well in advance of bud break as a conservative, bet-hedging strategy to insure the opportunity to form galls. Galls cannot be initiated until leaf buds begin to open, therefore aphids depend on tree phenology. Consequently, fundatrices that initiated galls later had both 1.9 times the mortality rate and 20% higher fecundity than those that initiated galls earlier, and trees that had later bud break had greater densities of galls.

KEY WORDS: gall, aphid, phenology, trade-off