Our model allows us to show that emergence of mutualism is made possible by selective ingestion (association). Migration selectivity does not allow the establishment of mutualism but increases its stability once it is established. Different attractors of the population dynamics correspond to the emergence of mutualism, predominance of "selfish" species, or coexistence of many species.
 Weisbuch, G. and G. Duchateau. (1993) Emergence of mutualism. Bull. of Math. Biology, 55, 6, 1063-1090.
 G. Duchateau-Nguyen, Weisbuch, G. and L. Peliti (1994) A compartimental model of mutualism. Journal of biological systems