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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.
Studies of ancient DNA and endogenous viral elements have revealed extraordinary conservation of virus genome sequences over thousands or millions of years. In this Opinion article, Simmonds, Aiewsakun and Katzourakis describe a niche-filling model that describes how viruses can rapidly evolve to adapt to new host environments while their longer-term evolution is increasingly driven by their hosts.
Herbivorous insects could diversify through radiations after major host switches or through constant variability in new host use. With phylogenetic and network analyses, Braga et al. show that variability in host use supports most butterfly diversification, while rare radiations can further boost diversity.
Associations between corals and symbiotic microorganisms could be driven by the environment or shared evolutionary history. Here, the authors examine relationships between coral phylogenies and associated microbiomes, finding evidence of phylosymbiosis in microbes from coral skeleton and tissue, but not mucus.
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
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.