February 22, 2011 Select this article Biological Sciences- Evolution: Ulrich G. Mueller, Alexander S. Mikheyev, Eunki Hong, Ruchira Sen, Dan L. Warren, Scott E. Solomon, Heather D. Ishak, Mike Cooper, Jessica L. Miller, Kimberly A. Shaffer, and Thomas E. Juenger Evolution of cold-tolerant fungal symbionts permits winter fungiculture by leafcutter ants at the northern frontier of a tropical ant–f..