Do mutualisms matter? Assessing the impact of pollinator and disperser disruption on plant extinction

Abstract

There is a voluminous literature on pollination and dispersal, very little of which deals with the consequences of reproductive failure and its most extreme consequence: extinction. The risk of plant extinctions can be assessed by considering the probability of dispersal or pollinator failure, reproductive dependence on the mutualism and demographic dependence on seeds. Traits for ranking species rapidly according to these three criteria are indicated. Analysis of case studies suggests that plants often compensate for high risk in one of the three categories by low risk in another. For example, selfincompatible plants with rare specialist pollinators often propagate vegetatively. Some systems, including elements of the Cape flora and lowland tropical rain forest, lack compensatory traits and the risk of plant extinction from failed mutualism is high. ‘What escapes the eye, however, is a much more insidious kind of extinction: the extinction of ecological interactions’ Janzen (1974).