coadaptation

Coadaptation is the process by which two or more traits, genes, or interacting species become adapted to one another through reciprocal selection, resulting in improved compatibility and fitness for the participants. The term encompasses both genetic coadaptation within an organism and coadaptation between species, where traits in interacting entities evolve in concert to enhance a mutual relationship or ecological interaction.

Within a single organism, intragenomic coadaptation occurs when combinations of alleles across different loci interact epistatically to produce a phenotype that functions more effectively than would be possible from any single allele alone. Examples can include immune system components that work together to recognize pathogens or metabolic pathways in which sets of enzymes are complementary. Such coadapted gene complexes can influence fitness and may contribute to reproductive isolation if incompatible combinations arise.

Between species, coadaptation describes reciprocal evolutionary changes that improve the interaction between organisms. In mutualistic relationships, traits such as floral morphology and pollinator mouthparts, or plant physiology and microbial symbionts, often track each other to maximize mutual benefit. In antagonistic associations, hosts and parasites may also coadapt, with defenses and offensive traits evolving in response to one another, potentially leading to escalation or stabilization of the interaction.

Coadaptation is studied through comparative genomics, experimental evolution, and ecological or behavioral studies aimed at identifying coevolved trait complexes. It is related to, but not always identical with, coevolution, as coadaptation emphasizes the evolved compatibility of interacting components and their fitness consequences.