Ecological and evolutionary consequences of spatial and temporal variation in pre-dispersal seed predation

Pre-dispersal seed predation may have important effects on population dynamics and trait evolution in plants. In this review, we first present a conceptual framework of the strength of pre-dispersal seed predation and its variation in space and time. We consider the interaction between plants and their seed predators to be “strong” when it affects plant population dynamics or causes changes in plant trait–fitness relationships, and “weak” when it has no such effects, and propose ways of how to adequately assess these effects. Second, we review the ecological literature between 1991 and 2005 to evaluate documented effects of pre-dispersal seed predation on plants and draw five major conclusions. (1) Pre-dispersal seed predation rates are usually low but sometimes high, and show a considerable variation in space and time. (2) Direct evidence suggests that pre-dispersal seed predation can have a significant effect on recruitment and plant population growth rate. Accumulating evidence of seed-limited recruitment suggests that such effects are common. (3) Pre-dispersal seed predation affects selection on several plant traits, such as flowering phenology and flower number, which are usually interpreted mainly in the context of plant–pollinator interactions. (4) The patterns of variation in the interactions between plants and pre-dispersal seed predators suggest that geographic selection mosaics may be common. (5) Although there are numerous studies estimating seed predation, there are still rather few studies that have aimed at examining the interaction explicitly in terms of effects on plant population dynamics and trait selection. From these we know that seed predators can have important, and often variable, effects on plant population dynamics and trait evolution. However, it still remains to assess how important they are across study systems and relative to other aspects of the plant's biotic and abiotic environment.