Allodiploidy

Allodiploidy is a term used in genetics to describe an organism that is diploid, meaning it has two sets of chromosomes, but these two sets are derived from two different ancestral species. This condition arises from hybridization between two distinct species, followed by a doubling of the chromosome number. The resulting allodiploid organism therefore possesses a complete genome from each of its parent species.

This phenomenon is distinct from autodiploidy, where an organism has two sets of chromosomes that are identical copies of a single ancestral genome. Allodiploidy is a common mechanism in the evolution of plants, and many crop species, such as wheat and cotton, are allodiploids. It can also occur in some animals, although it is less frequent.

The process of allodiploid formation typically involves the fusion of gametes from two different species, creating a hybrid that is usually sterile due to incompatible chromosome pairings during meiosis. However, if the chromosome number of this hybrid then doubles, the chromosomes can pair more effectively, leading to the restoration of fertility and the establishment of a new allodiploid lineage. Allodiploidy can lead to novel traits and increased genetic diversity, contributing to evolutionary innovation.