Coevolution

Chapter Summary

1. Coevolution occurs when evolutionary changes to traits in one species cause selection to act in new ways on traits in another species, which in turn feed back to alter the nature of selection on traits in the first species, and so forth.
2. Mutualisms may evolve from initially neutral interactions between species or from interactions in which one species initially benefits and the other is initially unaffected in any way. A mutualism can even evolve from an initially parasitic relationship when the costs and benefits of that parasitic relationship change over time to favor the mutualism.
3. Under certain conditions, natural selection may favor communication between individuals of different species involved in a mutualistic relationship.
4. If the benefits of mutualism to both species are high and the mutualistic relationship has been in place over a long period of evolutionary time, the link between mutualists may lead to cospeciation, in which speciation in one species is associated with speciation in the other.
5. The two most common forms of antagonistic coevolution are that between predator and prey, and that between parasite and host.
6. The dynamics of antagonistic coevolution can take the form of an evolutionary arms race.
7. Cospeciation may occur in parasite–host systems. Speciation in hosts can drive speciation in their parasites.
8. Natural selection can result in mutualism between a pair of species in some communities but antagonistic interactions between the same species in other communities. This leads to geographic variation in coevolutionary outcomes, or mosaic coevolution.
9. Evolutionary biologists and anthropologists have begun examining gene–culture coevolution and its consequences, both within and between species.