Allozyme markers from ten European taxa of Viola subsection Viola suggest t
hat this group is allotetraploid, based on x = 5. All taxa had distinct mul
tilocus phenotypes except V. alba subspp. alba and scotophylla, which were
identical and different from subsp. dehnhardtii. Variation was consistently
higher in Mediterranean populations than in North European ones. Hybridisa
tion seems extensive but putative F-1 hybrids were distinctly less fertile
than the parental species. Nevertheless, increased fertility in later-gener
ation hybrids and shared band patterns among taxa indicate an important rol
e of hybridisation and introgression in past and present evolution within t
he subsection. The octoploid V. ambigua shows affinity to V. hirta (tetrapl
oid). The octoploid V. suavis probably originated from V. pyrenaica and oth
er unidentified tetraploids, and high variability suggests polytopy or even
polyphyly. The stoloniferous condition (series Flagellatae) seems to be pr
imitive in the subsection but the reduction of stolons (series Eflagellatae
) may have originated multiple times.