Postdispersal seed predation limits the abundance of a long‐lived perennial forb (Lithospermum ruderale)

Abstract

Loss 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 postdispersal seed predation by rodents, as most studies of rodent seed predation have focused on the sources of spatiotemporal variation in seed loss but not quantified the population consequences of this loss. In previous work we showed that seed predation by deer mice (Peromyscus maniculatus) substantially reduced seedling recruitment and establishment of Lithospermum ruderale (Boraginaceae), a long-lived perennial forb. To shed light on how rodent seed predation and the near-term effects on plant recruitment might influence longer-term patterns of L. ruderale population growth, we combined experimental results with demographic data in stage-based population models. Model outputs revealed that rodent seed predation had a significant impact on L. ruderale population growth rate (lambda). With the removal of postdispersal seed predation, the projected population growth rates increased between 0.06 and 0.12, depending on site (mean deltalambda across sites = 0.08). Seed predation shifted 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. Simulations varying the magnitude of seed predation pressure while holding other vital rates constant showed that seed predation could lower lambda even if only 40% of available seeds were consumed. These results demonstrate that rodent granivory can be a potent force limiting the abundance of a long-lived perennial forb.

A continent‐wide study reveals clear relationships between regional abiotic conditions and post‐dispersal seed predation

“…seeded species, such as the one used in our study, are often seed-limited (Clark et al, 2007;Maron et al, 2012), suggesting that the patterns of granivory we observed may yield large-scale differences in the degree to which seed predation, rather than dispersal limitation or microsite limitation, affects the recruitment of some plant species (Orrock et al, 2006;Hillyer & Silman, 2010;Bricker & Maron, 2012;Maron et al, 2012;Germain et al, 2013). An additional implication of our findings is that future changes in climatic conditions may change the strength of plant-granivore interactions.…”

“…Granivory is an important plant-consumer interaction because the distribution and abundance of plants often hinges on the survival of their seeds (Crawley, 2000;Orrock et al, 2006;Clark et al, 2007;MacDougall & Wilson, 2007;Pearson et al, 2011;Bricker & Maron, 2012;Maron et al, 2012) and granivory can exert a strong influence over the diversity and composition of plant communities (e.g. Crawley, 2000;Howe & Brown, 2001;Pearson et al, 2011;Maron et al, 2012).…”

Effects of nitrogen deposition on reproduction in a masting tree: benefits of higher seed production are trumped by negative biotic interactions

“…Seed traits largely determine rodent predation and dispersal that act as strong ecological filters in plant communities (Howe & Brown ; Pérez‐Ramos et al . ; Bricker & Maron ). Thus, nitrogen‐mediated changes in seeds quality might alter preferences of seed predators potentially leading to shifts in composition of plant communities.…”

Native insect herbivory overwhelms context dependence to limit complex invasion dynamics of exotic weeds

“…; Miller et al . ; Bricker & Maron ), we combined data from the two interannual transitions, thus assuming no temporal variability. We fit the vital rate functions using generalised linear mixed‐effects models in a hierarchical Bayesian framework.…”