Predicted vs. observed network architecture.

<p>For each network, simulations were run to equilibrium and its architecture (modularity, nestedness, and connectance) recorded. Predictions are the averages of the last 200 time units after the dynamics stabilize.</p

Robustness of rigid and adaptive networks to species loss

<div><p>Controversies in the complexity-stability debate have been attributed to the methodologies used such as topological vs. dynamical approaches or rigid vs. adaptive foraging behaviour of species. Here, we use a bipartite network model that incorporates both topological and population dynamics to investigate the robustness of 60 real ecological networks to the loss of generalist and specialist species. We compare the response in both adaptive and rigid networks. Our results show that the removal of generalists leads to the most secondary extinctions, implying that conservation strategies should aim to protect generalist species in the ecosystem. We also show that adaptive behaviour renders networks vulnerable to species loss at initial stages but enhances long term stability of the system. However, whether adaptive networks are more robust to species loss than rigid ones depends on the structure of the network. Specifically, adaptive networks with modularity < 0.3 are more robust than rigid networks of the same modularity. Interestingly, the more modular a network is, the less robust it is to external perturbations.</p></div

Robustness vs. network structure.

<p>For each simulation, the model was ran up t = 150, after which its structure was recorded. The generalist species were sequentially removed and the level of robustness recorded. Panels show the relationship between robustness and connectance, link density, nestedness, resource-consumer ratio, skewness of the degree distribution and modularity in both adaptive and rigid networks. R50 was used as the measure of robustness. Cyan lines indicate regressions for adaptive networks (cyan dots) while red lines for rigid networks (red dots). Spearman’s rank correlation coefficients are summarised in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189086#pone.0189086.t001" target="_blank">Table 1</a>.</p

Spearman’s rank correlations between network structure and robustness (R50, is the percentage of generalist resources that need to be removed before at least 50% of consumer species go extinct).

<p>Spearman’s rank correlations between network structure and robustness (R50, is the percentage of generalist resources that need to be removed before at least 50% of consumer species go extinct).</p

Robustness to the removal of generalists and specialists in two networks (N41 and N43 in S1 Table).

<p>Points show the percentage of consumer extinctions that result from the removal of a certain percentage of resource generalists and specialists. Panels (a) and (b) correspond to adaptive networks while (c) and (d) correspond to rigid networks.</p