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, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Sets of chromosomes refer to the number of maternal and paternal chromosome copies, respective ...
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 and
G. Ledyard Stebbins in their 1938 monograph ''The American Species of ''Crepis'': their interrelationships and distribution as affected by polyploidy and apomixis''. In ''
Crepis'' 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 sex ...
of
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 taxonomist, tropical explorer, ornithologist, philosopher of biology, and historian of science. His w ...
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, polyploidy, or asexual reproduction.
[
]
See also
* Species complex
In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...
References
Genetics
Evolutionary biology