The incorporation of genes of one species into the gene pool of another. If the ranges of two species overlap and fertile hybrids are produced, they tend to backcross with the more abundant species. This process results in a population of individuals, most of which resemble the more abundant parents but that also possess some characters of the other parent species. Local habitat modification can lead to mixing of previously distinct gene pools. Introduced species (or subspecies) can generate extinction of the older species by hybridization and introgression. The use of molecular markers has greatly increased the ability to detect and quantify interspecific gene exchanges. For example, phylogenetic trees based on chDNAs have shown many examples of both recent and ancient exchanges of chloroplasts between sympatric species. See chloroplast DNA (chDNA), wolf.
Subjects: Genetics and Genomics.