coadapted

Coadapted is an adjective used in biology to describe systems or components that have become adapted to one another. In evolutionary biology, coadaptation refers to a process or state in which multiple genetic loci, or phenotypic traits, have evolved in concert so that specific combinations confer higher fitness than others. When such loci interact epistatically, they form a coadapted gene complex, a functional unit within a genome that is best suited to operate together in a particular environment or genetic background.

Coadapted traits can arise within a population through natural selection favoring certain allele combinations. Because recombination can break up these favorable combinations, populations may maintain distinct coadapted complexes, and introgression from divergent populations can reduce fitness, a phenomenon known as outbreeding depression.

Coadaptation is often discussed together with coevolution, which refers to reciprocal evolutionary changes between interacting species, such as hosts and parasites or pollinators and plants. Coadaptation can occur within a species’ genome or between interacting species, illustrating a spectrum from internal genetic integration to interspecific mutual influence.

Examples occur across contexts: in domesticated animals or crops, multiple loci may adapt together to human-managed environments; in host–microbiome relationships, a host’s genetic background can shape microbial communities in a coadapted manner; and in immune system evolution, receptor and signaling pathways can become jointly tuned to prevailing pathogens. Recognizing coadapted combinations helps explain why certain genetic or phenotypic configurations persist and why breaks in these combinations can reduce fitness.