Abstract
Hybridization and genetic introgression have recently drawn increasing attention in evolutionary studies. Since speciation events are mainly regarded as bifurcating phenomena occurring when an ancient population has divided into two species, hybridization has been treated as exceptional. However, recent molecular approaches, especially multi-locus analyses, have revealed the important role of introgressive hybridization. This review introduces recent avian research related to hybridization and genetic introgression. Such events may be grouped into four categories of occurrence, when: 1) two lineages continue to diverge, 2) two separate lineages fuse to become one, in a process known as “de-speciation” or “species fusion”, 3) a new lineage is formed by hybridization of two parental lineages, called “hybrid speciation”, and 4) two lineages are maintained and genetic introgression occurs between those lineages. The importance of studying hybridization and genetic introgression so as to be able to address conservation issues such as genetic contamination by invasive species, is also discussed.
