Population dynamics in compressible flows R. Benzi, M.H. Jensen, D.R. Nelson, P. Perlekar, S. Pigolotti and F. Toschi Eur. Phys. J. Special Topics, 204 (2012) 57-73 Published online: 17 April 2012 DOI: 10.1140/epjst/e2012-01552-0