1. Margulis, L., Matthews, C. & Haselton, A. (eds) Environmental Evolution 2nd edn (MIT Press, Cambridge, MA, 2000).
2. Dawkins, R. The Extended Phenotype (Oxford Univ. Press, Oxford, 1982).
3. Raven, J. A. Limnol. Oceanogr. 42, 198–205 (1997).
4. Verity, P. G. & Smetacek, V. Mar. Ecol. Prog. Ser. 130, 277–293 (1996).