Coevolution in mutualisms

While coevolution may have dramatically shaped our world, it has been extremely difficult to demonstrate because the signatures of coevolution are exceptionally diverse and they are seldom exclusive to coevolutionary processes. This chapter gives a brief history of how coevolution has been studied in mutualistic and antagonistic relationships and then suggests methods which can be used to demonstrate coevolution. There are several different potential mechanisms behind the coevolutionary process and these mechanisms are likely to differ between antagonisms and mutualisms as well as from one mutualism to another. Consequently it may be expected that the signatures of coevolution may differ depending on the exact mechanisms behind the process. It is suggested how to recognize those signatures and why the phenotypes and phylogenies of interacting species may sometimes match or mismatch, and how coevolution can cause patterns of trait diversification and convergence. While patterns associated with coevolution cannot be used to prove coevolution on their own, it is argued, they remain very useful tools to test predictions about how different kinds of coevolution and relationships may affect the phenotypic and genotypic evolution of interacting species.