“Network structure and selection asymmetry drive coevolution in species-rich antagonistic interactions”

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Cecilia S. Andreazzi, John N. Thompson, and Paulo R. Guimarães Jr.

The selective pressures imposed by ecological interactions are one of the forces shaping adaptation in populations. Coevolution, which is the reciprocal evolutionary change occurring in populations of species that interact, is one of the possible outcomes of the selective pressures imposed by interactions. A major challenge for evolutionary ecology is to understand if and how the coevolutionary process occurs when species interact with individuals of multiple species forming networks of interactions.

In a study appearing in The American Naturalist, researchers from Brazil and the United States have used mathematical modeling and numerical simulations to explore how network organization affects and is affected by selection in antagonistic ecological interactions such as parasitism, predation, and herbivory. They find that the joint effects of selection imposed by interaction partners and network organization shape species evolutionary and coevolutionary dynamics in predictable ways, favoring arms races, coevolutionary alternation, or both. Arms races tend to occur when the intensity of selection is stronger on victims than on exploiters. If selection on exploiters is stronger than on victims, coevolutionary alternation is favored by nested network organization, creating asymmetry in specialization between exploiters and victims and generating a hierarchy of preferred victims among exploiters.

Finally, their results highlight that coevolution not only is affected by network organization but also reshapes network organization: Higher modularity arises in antagonistic networks as an outcome of the coevolutionary process, emerging as a by-product of stronger selective pressures acting on exploiters. Read the Article