Patagonian Tree Gall (image) University of Wisconsin-Madison Share Print E-Mail Caption Tree galls on Patagonian beech trees were the first places researchers found the yeast Saccharomyces eubayanus in nature. Five hundred years ago, the yeast fused with the well-known bread and wine yeast Saccharomyces cerevisiae to form an interspecies hybrid that lets people cold brew lager beer. Credit Diego Libkind, Institute for Biodiversity and Environment Research, Bariloche, Argentina Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.