Interspecific facilitation in a guild of benthic marine herbivores.

Interspecific relationships and trophic function within the urchin guild are considered in light of experiments and observations performed in situ. Two conclusions are reached: 1) interactions between members of the guild contribute to its persistence, and 2) the plant-herbivore interactions so important in structuring this community can best be evaluated when guild members are treated as a unit. As with other mixed species trophic units, the mechanisms of interspecies facilitation operate to reduce the effects of predation and increase foraging efficiency.