Abstract
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.
Highlights
Human activities are continuously driving species extinction in many ecosystems, threatening their function and the provision of ecosystem services [1,2,3,4,5]
Whenever the rigid network was more fragile to species removal compared to the adaptive one at the beginning, it remained less robust till the end
In cases where the adaptive network was less robust at the beginning to species removal, after a certain threshold, it later always became more robust than the rigid one, suggesting that species adaptive behaviour enhances robustness it might initially enhance the fragility of networks
Summary
Human activities are continuously driving species extinction in many ecosystems, threatening their function and the provision of ecosystem services [1,2,3,4,5]. The stability of a complex dynamical system can be mathematically determined by analysing the local and asymptotic behaviours of its trajectories [11,12,13,14] Such Lyapunov stability analysis only reflects one facet of how systems respond to perturbations, and can become clumsy when the dimension and complexity of the system reaches certain levels, which is often the case for ecological networks [15]. Alternative methods have been designed that cater for other facets of network stability, especially for large and complex systems where the traditional methodology fails [16,17]. To this end, robustness has been proposed to capture how ecological networks respond to the loss of species (nodes in the network). There are a variety of definitions of robustness in literature, all have
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