Abstract

Ecological trophic networks may involve complex interactions where the loss of a single species could trigger a cascade of secondary extinctions. However, such effects are not easily analyzed or interpreted due to low resolution and different characteristics of the available networks. In this regard, prior studies of empirical, high-resolution marine food webs (see below) found that these networks are characterized by few persistent trophic interactions and a large number of transient trophic interactions. Such pattern suggests that weak, transient interactions should be redundant to maintain the stability of the whole network, and therefore we hypothesized that, if coastal marine network are dominated by redundant trophic interactions, network's robustness should maintain over time even in the face of species losses. We thus analyzed and compared the network topological properties and robustness of four rocky intertidal assemblages along the coast of northern Chile, each one evaluated ten times through time, in correspondence with seasonal samples from summer 2005 and autumn 2007 (i.e. a total of 40 networks). For the robustness analysis of each network, we simulated a sequential extinction of species from the most to the least connected, based on a topological approach. The results showed that robustness was invariable over time, supporting the hypothesis and highlighting the importance of weak trophic interactions in natural communities. We review the criteria for selecting and analyzing species' deletion sequences, and discuss ecological and evolutionary mechanisms that may maintain network stability.