Acknowledgments
We thank Hossein Moradi, Melanie Aardalsbakke, Eva Vojtech and Daniel Trujillo for field assistance and Forest Isbell and Adam Clark for useful discussions on the relationship between RGR andR */I *. Pengfei Zhang was funded by the azi.cn site by the Key Program of the National Natural Science Foundation of China (No. 41430749) and supported by Chinese Scholarship Council (CSC) joint PhD scholarship. Yann Hautier was funded by Swiss National Foundation grant 3100A0-107572 to Andy Hector.