Michel Loreau | Search bioRxiv

bioRxiv2016

Particularity of “Universal resilience patterns in complex networks”

In a recent Letter to Nature,Gao, Barzel and Barabasi 1 describe an elegant procedure to reduce the dimensionality of complex dynamical networks, which they claim reveals \"universal patterns of network resilience\", offering \"ways to prevent the collapse of ecological, biological or economic systems, and guiding the design of technological systems resilient to both internal failures and environmental changes\". However, Gao et al restrict their attention to systems for which all interactions between nodes are mutualistic. Since antagonism is ubiquitous in natural and social networks, we clarify why this stringent hypothesis is necessary and what happens when it is relaxed. By analyzing broad classes of competitive and predator-prey networks we provide novel insights into the underlying mechanisms at work in Gao et als theory, and novel predictions for dynamical systems that are not purely mutualistic.

Ecology↗

bioRxiv2016

Environmental responses, not species interactions, determine species synchrony in natural plant communities

Temporal asynchrony among species helps diversity to stabilize ecosystem functioning, but identifying the mechanisms that determine synchrony remains a challenge. Here, we refine and test theory showing that synchrony depends on three factors: species responses to environmental variation, interspecific interactions, and demographic stochasticity. We then conduct simulation experiments with empirical population models to quantify the relative influence of these factors on the synchrony of dominant species in five semiarid grasslands. We found that the average synchrony of per capita growth rates, which can range from 0 (perfect asynchrony) to 1 (perfect synchrony), was higher when environmental variation was present (0.62) rather than absent (0.43). Removing interspecific interactions and demographic stochasticity had small effects on synchrony. For the dominant species in these plant communities, where species interactions and demographic stochasticity have little influence, synchrony reflects the covariance in species responses to the environment.

Ecology↗