Print PageLoss of seeds to consumers is common in plant communities, but the degree to which these losses influence plant abundance or population growth is often unclear. This is particularly the case for post-dispersal seed predation by rodents, as most studies of rodent seed predation have simply quantified spatio-temporal variation in the magnitude of seed loss. In previous work, we showed that seed predation by deer mice (Peromyscus maniculatus) substantially reduced the seedling recruitment of Lithospermum ruderale (Boraginaceae), a long-lived perennial forb. To shed light on how relatively short-term rodent-driven reductions in seed abundance and plant recruitment might influence longer-term patterns of Lithospermum population growth, we combined experimental results with demographic data in stage-based population models.
Results/Conclusions
Model outputs revealed that rodent seed predation had a significant impact on Lithospermum population growth rate (Λ). With the removal of post-dispersal seed predation, projected population growth rates increased between 0.02 and 0.10, depending on site. Simulations varying the magnitude of seed predation pressure while holding other vital rates constant showed that seed predation caused significant declines in l after 40% of seeds were consumed. Seed predation shifts the projected stable stage distribution of populations from one with a high proportion of young plants to one in which larger adult size classes dominate. Elasticities of vital rates also changed, with germination and growth of seedlings and young plants becoming more important with the removal of seed predation. These results demonstrate that rodent granivory can be a potent force limiting the abundance of a perennial forb.
