ABSTRACT
Coevolution is an evolutionary process that prompts the genetic adaptation of a species in response to the natural selection imposed by another interacting species and the effects might be reciprocal. The process of coevolution between plants and the surrounding biota including viruses, fungi, bacteria, nematodes, insects, and mammals is considered by many biologists to have generated much of the earth's biological diversity. In natural ecosystem, variation in the genetic structure of pathogen population and the respective host is determined by a specific gene-for-gene coevolution. It is a form of reciprocal genetic change occurring in the two ecologically interacting species: the pathogen and its host. The strength of coevolution varies between populations of interacting organisms. The geographic mosaic theory predicts that the three processes lead to three observable patterns: spatial variation in the traits mediating an interspecific interaction, trait mismatching among interacting species (local maladaptation), and a few species-level coevolved traits.
