Just when I thought that I was getting a handle on this. I’ve decided to begin exploring topological extinction with a simple 3 guild metanetwork.This example shows three guilds, a producer, primary consumer and secondary consumer. The guild diversities (species richnesses and producer nodes) are 250, 25 and 5 respectively. I then proceeded to do four things.
FIrst, I conducted 100 CEG simulations of bottom-up, primary producer disruption of the system. The results are shown in the second figure, and illustrate the typical CEG response. Note, however, that past the threshold point that there is a subset of networks which continue to exhibit high levels of resistance to secondary extinction.
Next, I conducted simulations of topological extinction only. The results are shown in the third figure. The differences are quite dramatic. There are definitely two different types of networks here. One set seems to show the typical CEG result, and another set exhibits high secondary extinction at low levels of perturbation. It seems that the removal of top-down cascades and compensatory effects removes some sort of control or enhancement of resistance! And finally, superimposed on these results are results of estimating topological extinction as outlined in the previous posts. The two curves show two different ways of doing it. The lower curve (green) is a continuous interpretation of the link distributions, while the upper curve simply rounds results to integers, so that links (and lost links) come in integers only. BUT, the good news is that the analytical estimates of topological extinction provide a very nice match to the lower subset of the topological simulation results.
Why, however, are the simulation results divided into two subsets?