This rule introduces random, small changes into the network. If the th species goes extinct, then all the connections that define it are set to zero, that is . This updating introduces extinction and selection of species. Those sets of connections which make a species stable will remain. But in removing a given species, some positive connections, with a stabilizing effect on other species can also disappear, and the system can become more unstable.
Diversification then is introduced.
The new species are basically identical to the one randomly choosen, except for a small random change in all their connections. Specifically, let the copied species. In this way, the new species are the result of the diversification of one of the survivors. The previous rules can be sumarized in figure 3, where a small ecosystem is shown. All of them are generated by the same dynamical process, and no particular extinction size is privileged.