autopolyploids

Autopolyploids are polyploid organisms in which multiple chromosome sets originate from a single species. In contrast to allopolyploids, which arise from hybridization between distinct species followed by genome doubling, autopolyploids contain several complete genomes that are homologous rather than homeologous. This means the extra chromosome sets come from the same genome, not from different species.

Autopolyploidy commonly forms when a diploid organism produces unreduced gametes (2n) or when a somatic chromosome doubling event occurs, yielding zygotes with four, six, or more sets of chromosomes. Such events can happen spontaneously in nature or be induced experimentally in breeding programs. The resulting organisms may be triploid, tetraploid, or of still higher ploidy, depending on the mechanism and the parent’s ploidy.

Meiosis in autopolyploids is often characterized by polysomic inheritance, where homologous chromosomes can pair with multiple partners. This can produce multivalents such as quadrivalents in tetraploids, leading to irregular chromosome segregation and reduced fertility. Some autopolyploids mitigate these issues through mechanisms that favor more regular pairing, or through chromosomal rearrangements. Double reduction can also occur, affecting inheritance patterns.

Ecological and evolutionary consequences include the potential for immediate reproductive isolation from the diploid progenitor, contributing to speciation. Autopolyploids often exhibit larger cell size and sometimes larger organs, with gene redundancy providing material for adaptation; however, fertility can be reduced in odd-numbered ploidy levels and in early generations until genome stabilization.

Common plant examples include potato (Solanum tuberosum) and alfalfa (Medicago sativa), both of which are autotetraploids. Autopolyploidy is widespread in plants and may be targeted in crop improvement to fix desirable traits.