© 2005 British
Blackwell Publishing, Ltd.
Factors affecting the expression of inducible defences
in Euplotes: genotype, predator density and experience
S. L. DUQUETTE, R. ALTWEGG* and B. R. ANHOLT
Department of Biology, University of Victoria, Box 3020, Victoria, British Columbia, Canada V8W 3N5
1. Inducible defences alter the strength of interaction in food webs. Their effectiveness
depends both on the maximum level of induction and the speed at which induction
happens. Maximum level and speed of induction should therefore evolve in concert.
2. We examined the effect of genotype, number of predators and previous exposure to
predators on speed and maximum level of induction in a morphological defence
expressed by eight clones in three species of the ciliate Euplotes.
3. Bothspeedandmaximumlevelof induction,andthereactiontopredatordensityvaried
among genotypes. These results show that there is genetic variance for all aspects of this