Michele Bellingeri - Università degli Studi di Parma #
Robustness of complex ecological networks #
Food webs are ecological complex networks describing trophic relationships
among species in ecosystems.Notions of system robustness to node loss, and
of error and attack sensitivity were first introduced in the physical
literature and then successfully applied to the study of food webs. We use
simulations to test the robustness of 14 empirical food webs to species loss
by varying a parameter I (intentionality) that defines the removal
probability (extinction risk) of species with high number of trophic
connections. The removal probability of highly connected species (nodes)
increases with I. We found that food web robustness decreases slowly when
the extinction risk of highly connected species increases (we call this
region random removal regime), until a threshold value of I is reached. For
greater values of the threshold, we found a dramatic reduction in robustness
with increasing intentionality in almost all the food webs (intentional
attack regime).The existence of a clear transition in system behaviour has
relevant consequences for the interpretation of extinction patterns in
ecosystems and prioritizing species for conservation planning.