A polyploid complex, also called a diploid-polyploid complex, is a group of interrelated and interbreeding species that also have differing levels of

ploidy Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Sets of chromosomes refer to the number of mat ...

that can allow

interbreeding In biology, a hybrid is the offspring resulting from combining the qualities of two organisms of different breeds, varieties, species or genera through sexual reproduction. Hybrids are not always intermediates between their parents (such as in ...

. A

polyploid Polyploidy is a condition in which the cells of an organism have more than one pair of ( homologous) chromosomes. Most species whose cells have nuclei ( eukaryotes) are diploid, meaning they have two sets of chromosomes, where each set contain ...

complex was described by

E. B. Babcock Ernest Brown Babcock (July 10, 1877 – December 8, 1954) was an American plant geneticist who pioneered the under standing of plant evolution in terms of genetics. He is particularly known for seeking to understand by field investigations and e ...

and

G. Ledyard Stebbins George Ledyard Stebbins Jr. (January 6, 1906 – January 19, 2000) was an American botanist and geneticist who is widely regarded as one of the leading evolutionary biologists of the 20th century. Stebbins received his Ph.D. in botany from Har ...

in their 1938 monograph ''The American Species of ''Crepis'': their interrelationships and distribution as affected by polyploidy and apomixis''. In ''

Crepis ''Crepis'', commonly known in some parts of the world as hawksbeard or hawk's-beard (but not to be confused with the related genus ''Hieracium'' with a similar common name), is a genus of annual and perennial flowering plants of the family Aster ...

'' and some other perennial plant species, a polyploid complex may arise where there are at least two genetically isolated diploid populations, in addition to auto- and allopolyploid derivatives that coexist and interbreed. Thus a complex network of interrelated forms may exist where the polyploid forms allow for intermediate forms between the diploid species that are otherwise unable to interbreed. This complex situation does not fit well within the

biological species concept The species problem is the set of questions that arises when biologists attempt to define what a species is. Such a definition is called a species concept; there are at least 26 recognized species concepts. A species concept that works well for se ...

Ernst Mayr Ernst Walter Mayr (; 5 July 1904 – 3 February 2005) was one of the 20th century's leading evolutionary biologists. He was also a renowned Taxonomy (biology), taxonomist, tropical explorer, ornithologist, Philosophy of biology, philosopher o ...

which defines a species as "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups". In many diploid-polyploid complexes the polyploid hybrid members reproduce asexually while diploids reproduce sexually. Thus polyploidy is related to the phenomenon called "geographic parthenogenesis" by zoologist Albert Vandel,{{citation , author=Vandel, A. , year=1928 , title=La parthénogenèse géographique: Contribution à l'étude biologique et cytologique de la parthénogenèse naturelle. I , journal=Bulletin Biologique de la France et de la Belgique , volume=62 , pages=164–281 that asexual organisms often have greater geographic ranges than their sexual relatives. It is not known which of the associated factors is the major determiner of geographic parthenogenesis,

hybridization Hybridization (or hybridisation) may refer to: *Hybridization (biology), the process of combining different varieties of organisms to create a hybrid *Orbital hybridization, in chemistry, the mixing of atomic orbitals into new hybrid orbitals *Nu ...

, polyploidy, or asexual reproduction.

References

Genetics Evolutionary biology

See also

References