Acknowledgements
We gratefully acknowledge funding from the National Science Foundation (DEB1354224 to E.C. and DEB1354022 to N.M.W.) and the Swedish Research Council (grant 330-2014-6439 to M.R.). We thank Katie Burns, Arvid Lindh, Clara Stuligross, John Mola, Jessica Drost, Charley Nye, Kimiora Ward, and Staci Cibotti for their assistance in the field and laboratory. We are also grateful to the landowners and managers of Yolo, Colusa and Solano counties who permitted us to use their properties as field sites.