Polyploid complex

A polyploid complex is a group of interrelated and interbreeding plants that also have differing levels of ploidy that can allow genetic exchanges between unrelated species.

The polyploid complex was first 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 herbaceous perennial species, a polyploid complex may arise where there are at least 2 genetically isolated diploid populations, in addition to auto- and allopolyploid derivatives that coexist and interbreed (hybridise). Thus a complex network of interrelated forms may exist where the polyploid forms allow for genetic exchange between the diploid species that are otherwise unable to breed.

A polyploid complex has also been well described in Glycine.

This complex situation does not fit well within the biological species concept of Ernst Mayr which defines a species as "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups".