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

John L. Orrock, Elizabeth T. Borer, Lars A. Brudvig, Jennifer Firn, Andrew S. MacDougall, Brett A. Melbourne, Louie H. Yang, Dirk V. Baker, Avi Bar-Massada, Michael J. Crawley, Ellen I. Damschen, Kendi F. Davies, Daniel S. Gruner, Adam D. Kay, Eric Lind, Rebecca L. McCulley, Eric W. Seabloom
Large-scale patterns linking energy availability, biological productivity and diversity form a central focus of ecology. Despite evidence that the activity and abundance of animals may be limited by climatic variables associated with regional biological productivity (e.g. mean annual precipitation and annual actual evapotranspiration), it is unclear whether plant–granivore interactions are themselves influenced by these climatic factors across broad spatial extents. We evaluated whether climatic conditions that are known to alter the abundance and activity of granivorous animals also affect rates of seed removal.

Eleven sites across temperate North America.

We used a common protocol to assess the removal of the same seed species (Avena sativa) over a 2-day period. Model selection via the Akaike information criterion was used to determine a set of candidate binomial generalized linear mixed models that evaluated the relationship between local climatic data and post-dispersal seed predation.

Annual actual evapotranspiration was the single best predictor of the proportion of seeds removed. Annual actual evapotranspiration and mean annual precipitation were both positively related to mean seed removal and were included in four and three of the top five models, respectively. Annual temperature range was also positively related to seed removal and was an explanatory variable in three of the top four models.

Main conclusions
Our work provides the first evidence that energy and precipitation, which are known to affect consumer abundance and activity, also translate to strong, predictable patterns of seed predation across a continent. More generally, these findings suggest that future changes in temperature and precipitation could have widespread consequences for plant species composition in grasslands, through impacts on plant recruitment.