QUANTITY, QUALITY AND THE EFFECTIVENESS OF SEED DISPERSAL BY ANIMALS

Disperser effectiveness is the contribution a disperser makes to the f uture reproduction of a plant. Although it is a key notion in studies of seed dispersal by animals, we know little about what determines the effectiveness of a disperser. The role of the present paper is to rev iew the available information and construct a hierarchical framework f or viewing the components of disperser effectiveness. Effectiveness ha s both quantitative and qualitative components. The quantity of seed d ispersal depends on (A) the number of visits made to the plant by a di sperser and (B) the number of seeds dispersed per visit. The quality o f seed dispersal depends on (A) the quality of treatment given a seed in the mouth and in the gut and (B) the quality of seed deposition as determined by the probability that a deposited seed will survive and b ecome an adult. In this paper I review the ways disperser behavior, mo rphology and physiology can influence these major components of disper ser effectiveness, and when data permit present preliminary analyses o f relationships among components.