| 1990-1991 | Teaching Assistant, Institute of Theoretical Physics, University of Aachen
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| 1991-1992 | Consultant, Dynamics of Computation Group, Xerox Palo Alto Research Center, CA
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| 1992-1994 | Research Assistant, Theoretical Ecology Group, Research Center Jülich
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| 1994-1995 | Research Scholar, Neurodynamics Group, Research Center Jülich, Germany
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| 1995 | Research Scholar, Institute of Evolutionary and Ecological Sciences, Leiden University
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| 1996 | Research Fellow, Institute for Advanced Study, Wissenschaftskolleg zu Berlin, Germany
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| 1996-2001 | Project Coordinator, Adaptive Dynamics Network, International Institute for Applied Systems Analysis, Laxenburg
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| 2001-2004 | Project Leader, Adaptive Dynamics Network, International Institute for Applied Systems Analysis, Laxenburg
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| 2004-2005 | Program Leader, Adaptive Dynamics Network, International Institute for Applied Systems Analysis, Laxenburg
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| 2006-2013 | Program Leader, Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg
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| since 2014 | Program Director, Evolution and Ecology Program, International Institute for Applied Systems Analysis, Laxenburg |
