autoploidia

Autoploidia, or autopolyploidy, is a form of polyploidy in which an organism has more than two complete chromosome sets, all derived from a single species. This contrasts with allopolyploidy, where the extra chromosome sets come from different species. Autopolyploidy typically arises when genome duplication occurs within an individual or when unreduced (diploid) gametes fuse, producing offspring with three or more chromosome sets. Somatic doubling of chromosomes (endoreduplication) can also generate autopolyploid lineages.

In meiosis, autopolyploids face challenges because homologous chromosomes can pair with more than two partners, leading to irregular segregation and reduced fertility. Triploids are often largely sterile due to unbalanced chromosome sets, while some autotetraploids achieve more regular meiosis and can be fertile. Fertile autotetraploids may stabilize meiosis by diploid-like pairing, effectively behaving as two homologous chromosome sets during gamete formation.

Plants show autopolyploidy more commonly than animals. It occurs spontaneously in many plant lineages and can be exploited in breeding to create polyploid crops with desirable traits such as larger cell size and sometimes increased vigor. A classic example is the autotetraploid potato (Solanum tuberosum), widely cultivated and used in agriculture. Autopolyploidy can also contribute to speciation and ecological adaptation by creating reproductive isolation from the diploid progenitors.

In animals, autopolyploidy is comparatively rare but has been documented in certain fish and amphibian lineages.