Quantity, quality and the effectiveness of seed dispersal by animals

Abstract

Disperser effectiveness is the contribution a disperser makes to the future reproduction of a plant. Al- though 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 review the available information and construct a hierarchical framework for viewing the components of disperser effectiveness. Effectiveness has both quantitative and qualitative components. The quantity of seed dispersal de- pends on (A) the number of visits made to the plant by a disperser and (B) the number of seeds dis- persed per visit. The quality of 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 become an adult. In this paper I review the ways disperser behavior, morphology and physiology can influence these major components of disperser effectiveness, and when data permit present preliminary analyses of relationships among components.