Feeding preferences of gammarid amphipods among four species ofFucus

Each of fourFucus species occurring on the Atlantic coast of Canada was presented to two species of gammarid amphipods in no-choice and multiple-choice laboratory experiments. We also measured concentrations of anti-herbivore phlorotannins in each of theFucus species. The study site was Cranberry Cove in Nova Scotia, Canada, and experiments were conducted in 1988. In a multiple-choice experiment,F. vesiculosus was very heavily grazed. Other species were much less affected. In a no-choice experiment,F. evanescens, F. spiralis andF. vesiculosus were eaten at similar rates, whileF. distichus was barely grazed. These results correlate with measurements of phorotannin concentrations in each of the species.F. distichus had much higher concentrations than did the other species (which were not significantly different among themselves). There is no general clear-cut relationship between grazer deterrence and competitive capability within the fucoid guild studied.