PARENT SESSION
Oral Session #38: Herbivory: Herbivore Response to Plants. Presiding: P. Kleintjes.
Tuesday, August 7, 2001. 1:00 PM to 4:30 PM. Hall of Ideas J.
A strong relationship between preference and performance in a spittlebug.
Craig, Timothy1, Ohgushi, Takayuki2, 1 2
ABSTRACT- There was a positive correlation between oviposition and feeding preferences and offspring performance in the spittlebug, Aphrophora pectoralis Matsumura (Homoptera, Aphrophoridae) on four species of willows, Salix sp. (Salicaceae) growing near Sapporo, Japan. Spittlebugs preferred rapidly growing shoots where performance was highest on all host species. Egg densities on three of the four willow species corresponded with offspring performance, when the effects of shoot length were removed. The exception was Salix hultenii where nympal survival was high, but which had low egg densities. Adult movement pattern may explain this low egg density. Spittlebugs aggregated almost exclusively on Salix sachalinensis for feeding and mating, and subsequently females dispersed to other species to oviposit. S. hultennii was rare and frequently distant from S. sachalinensis and we hypothesize that this makes it costly to locate. Nymphs dispersed from the oviposition site to feed on nearby shoots within a host plant willows. Nymphs preferred rapidly growing shoots, thus refining the female choice by moving from the eggmass to nearby larger shoots. Such a strong preference-performance correlation is unusual for polyphagous species with a mobile immature stage and similar to that found in sedentary herbivores such as gall-inducers. We propose that the phylogenetic constraint of being adapted to oviposit into growing tissue has facilitated the evolution of a strong preference-performance relationship, and that the dispersal of offspring did not significantly weaken this relationship.
KEY WORDS: spittlebug, preference-performance, herbivory, Salix