The Spandrels of Ecological Networks

2018 edition

Jordi Piñero

Networks pervade natural systems. Interaction webs play a big role in ecology. The term ‘mutualist’ refers to pairs of species that interact in a cooperative manner. For example, plant-animal interactions of the type: flower-bee, etc. Networks of mutualistic species are of special interest in ecology, as they manifest universal statistical patterns, i.e., global structural regularities present in different webs of mutualistic species. These have been suggested to emerge from potential selection processes favouring the observed web organization. However, here (1) we show that these structural quantitative patterns can be properly explained by means of a very simple dynamical model of speciation and divergence with no selection-driven coevolution of traits.The agreement between observed and modelled networks suggests that the patterns displayed by the studied mutualistic webs might actually represent evolutionary byproducts of the network generative process, which are defined as evolutionary spandrels (2).

(1) Sergi Valverde, Jordi Piñero, Bernat Corominas-Murtra, Jose Montoya, Lucas Joppa & Ricard Solé “The architecture of mutualistic networks as an evolutionary spandrel“. Nature Eco. & Evo. (2017).

(2) Stephen J. Gould  & Richard C. Lewontin, “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme”. Proc. R. Soc. Lond. B 205, 581–598 (1979)