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Video abstract for the article 'Mesoscale symmetries explain dynamical equivalence of food webs' by Helge Aufderheide, Lars Rudolf and Thilo Gross (Helge Aufderheide et al 2012 New J. Phys. 14 105014). Read the full article in New Journal of Physics at http://iopscience.iop.org/1367-2630/14/10/105014/article. Part of Focus on Soft Mesoscopics: Physics for Biology at a Mesoscopic Scale GENERAL SCIENTIFIC SUMMARY Introduction and background. The dynamics of ecological systems can be incredibly complex. The sheer diversity of biological life leads to complex networks of interactions. The relevant time scales range from hours in the microscopic world to decades and even centuries for long-lived macroscopic animals. Even in simplified models describing a food web, the network of who-eats-who, one typically finds a multitude of different dynamics and dynamical transitions, so-called bifurcations. Main results. All the more surprising was a recent finding that the dynamics of different food webs can be characterized by identical bifurcation diagrams, when viewed from the right angle. In other words, they present an example of different dynamical systems exhibiting identical phase diagrams. The present paper provides an analytical explanation for this observation, showing that the symmetry between systems is caused by meso-scale symmetry in the system's structure. Under certain conditions, identifying such internal symmetries allows aggregating the system, such that a smaller system with identical dynamics is formed. Wider implications. Beyond the importance for ecosystems research, this work provides an example for the importance of meso-scale structures in complex networks.