Native granivores reduce the establishment of native grasses but not invasive Bromus tectorum
Seed predation can structure plant communities by imposing strong population controls on some species but not others. In this context, studies from various ecosystems report that native granivores selectively forage for seeds from native species over seeds from exotic invaders, which could disproportionately favor the establishment of invaders and facilitate their dominance in communities. However, few studies have connected selective foraging for native seeds to differential patterns of establishment among native and invasive species. Thus, the extent to which preferential foraging for native seeds favors the establishment of invasive plants is unclear. Here, we used experimental seed additions and exclosure treatments at five field sites distributed across ≈ 80,000 km2 of the Great Basin Desert, USA to compare the effects of rodent foraging on the establishment of less-preferred cheatgrass (Bromus tectorum—an annual species native to Eurasia that is exotic and highly invasive across the Great Basin) and four species of more-preferred native grasses that commonly co-occur with cheatgrass. Rodent foraging reduced the establishment of each native species by at least 80% but had no effect on the establishment of cheatgrass, and this finding was consistent across study sites. Our results suggest that selective foraging for native species may favor the establishment of cheatgrass over native grasses, potentially exacerbating one of the most extensive plant invasions in North America.
KeywordsBromus tectorum Enemy release hypothesis Great Basin Rodents Seed predation
The authors are grateful for funding from the Montana Institute on Ecosystems, the National Science Foundation Established Program to Stimulate Competitive Research Track-1 EPS-1101342 (INSTEP 3), the Organismal Biology and Ecology Program at The University of Montana, and the American Museum of Natural History. We also thank Dean Pearson and John Maron for insightful comments that improved our work.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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