Does increasing the diversity of seeds broadcast for restoration alter post-dispersal seed predation and its community-determining effects?
Abstract
Native seeds broadcast for restoration are often consumed by predators before they can germinate. However, it is unclear how the composition of a seed mix affects seed predation. We excluded vertebrates from small plots seeded with native grassland plants to evaluate how seed diversity affects predation. There were two seeding treatments: a less diverse mix with a focal cohort of eight species on which we focused our analyses, and a more diverse mix that consisted of the focal cohort plus eight additional species. The focal cohort experienced greater predation when dispersed with the additional species, but this effect was unevenly distributed throughout the focal cohort. The species of the focal cohort that experienced the greatest increase in predation when in the high-diversity treatment were also the ones favoured by predators when in the treatment without additional species. This suggests that when more species of palatable seed are available in a dispersed seed patch, predators may exert a stronger community-filtering effect on such a seed patch. Increasing the number of species dispersed together for land stewardship efforts may increase predation of these seeds, which is a concern if their dispersal is intended to restore native plant diversity. We recommend strategies to minimize this potential detriment, such as staggering seed dispersal over time, for practitioners who seek to disperse a high diversity of seeds for native restoration.