Coevolution and Macroevolution

Abstract

Coevolution is reciprocal evolution of interacting species driven by natural selection. Selection imposed by interactions between or among species can cause trait changes that alter ecological outcomes, patterns of local adaptation, and diversification of lineages. For example, selection can reduce the effect of the interaction when one species suffers a loss in fitness (antagonistic interactions) or increase the effect when species benefit from the association (mutualistic inter-actions). The selected traits may either change the cost of the interaction or the probability that the interaction occurs at all. These evolutionary changes can lead to local coadaptation as interacting species adapt and counteradapt to one another over time. In some cases, one or more of the locally coadapted species may become reproductively isolated from other populations as local coevolution decreases the chance of mating among populations. This cessation of gene flow, coupled with further evolutionary change, could lead to the formation of nascent species. There is, then, a direct potential connection between local coadaptation of populations, speciation, and macroevolutionary diversification. Some of the most challenging questions in coevolutionary biology center on understanding how coevolving traits change as they are expressed in a diversity of genetic and environmental backgrounds, how such traits can directly or indirectly lead to reproductive isolation, and whether these traits are likely to cause recurrent patterns of speciation that produce macroevolutionary patterns. considers what is currently known about the steps of this hierarchical process of evolutionary, and sometimes coevolutionary, diversification of interactions among species and how shifts in development may play an instrumental role in diversification.