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Coevolution is the process by which two or more species evolve in tandem by exerting selection pressures on each other. Examples of coevolutionary systems include host and parasites, predators and prey, and mutualistic or symbiotic interactions.
Host-parasite coevolution can lead to arms races favouring novel immunogenetic alleles or the maintenance of diversity in a balanced polymorphism. Here, Lighten et al. combine data on MHC diversity across three guppy species and simulations to show that polymorphisms of immunogenetic supertypes may persist even as alleles within supertypes are involved in an arms race.
An approach to ecological interactions that integrates coevolutionary dynamics and network structure, showing that selection in mutualisms is shaped not only by the mutualistic partners but by all sorts of indirect effects from other species in the network.
In a remarkable example of convergent evolution, insect species spanning 300 million years of divergence have evolved identical single-amino-acid substitutions that confer resistance to plant cardenolide toxins.
Marine cyanobacteria can shrug off viral assault by inactivating the genes involved in virus attachment. But this strategy has a cost: it may affect cell fitness or even favour infection by other viruses. See Article p.604