Environmental damage caused by human activity can reduce the number of plant and animal species dramatically. At the same time, very little is known about how biodiversity recovers after ecosystem pollution is curtailed and has been cleaned up. As was common in the mid-1900s, Lake Constance, one of the largest freshwater lakes in Europe, suffered from eutrophication, or nutrient contamination caused by agricultural and waste water run-off. A study by the universities in Konstanz and Glasgow has now revealed that one European whitefish species expanded its genetic variation through hybridization with other whitefish species during the period of eutrophication. The study, led by the Konstanz-based biologist Dr. Jasminca Behrmann Godel along with her colleague Dr. Kathryn R. Elmer from the University of Glasgow, was published in the journal Nature Ecology and Evolution. This genetic mixture contributed to an expansion in biodiversity once the ecosystem recovered.