Genetic variability in obligate apomicts of the genus Taraxacum

To test whether obligate apomicts can generate genetic variability, the only valid procedure is to investigate heritable variation amongst the offspring of fully agamospermous mothers. Among plants, most reports have been for Taraxacum, and this review concentrates on this genus, although there are many analogous reports for animals. In Taraxacum, within-family variation is commonly found at the levels of ploidy, aneuploidy, recombination and single gene mutation. Faulty disjunction, somatic recombination due to transposon activity, and mutation are all implicated. Although such asexual variation should generate evolutionary change, and there is clear evidence that this has occurred, evolutionary patterns will differ fundamentally from those of outcrossing sexuals. As asexual matrilineal lines cannot shed or disseminate mutational loads, three dimensional relationships are dichotomously dendroid rather than reticulate.