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The assembly rules and how stable food webs can evolve


Dr. Jan Haerter

Professor/a organitzador/a

lex Arenas


Universitat de Barcelona


19-10-2015 12:30


Debate continues as to whether large food webs can be dynamically stable and feasible. Further, it is unclear under which circumstances they can emerge, maintaining stability upon every evolutionary step. Using generalized Lotka-Volterra equations, we first show how food webs can be assembled from a single species. Invaders are given a single resource and our theory predicts which additions allow for stable coexistence. Perturbing the resulting network backbone by additional weak interactions demonstrates that large food webs of arbitrary connectivity can exist. Such bimodal link-strength distributions are supported by field measurements. Based on the dynamical equations, we further devise a recursive procedure for calculating extinction cascades after each species addition. The evolved tree-like food webs display self-similar fitness hierarchies and species life times in accordance with the fossil record. The invasion dynamics finally suggests a parameter-free invasion extinction model (IEM) involving random coefficients that each represent fitness parameters in the Lotka-Volterra equations. Our model thereby serves as a coherent starting point for the study of biodiversity loss in more complex food webs.


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