Allozymic variation and relationships within Viola subsection Viola (Violaceae)

Allozyme markers from ten European taxa of Viola subsection Viola suggest that this group is allotetraploid, based on x = 5. All taxa had distinct multilocus 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. Hybridisation seems extensive but putative F-1 hybrids were distinctly less fertile than the parental species. Nevertheless, increased fertility in later-generation hybrids and shared band patterns among taxa indicate an important role of hybridisation and introgression in past and present evolution within the subsection. The octoploid V. ambigua shows affinity to V. hirta (tetraploid). The octoploid V. suavis probably originated from V. pyrenaica and other unidentified tetraploids, and high variability suggests polytopy or even polyphyly. The stoloniferous condition (series Flagellatae) seems to be primitive in the subsection but the reduction of stolons (series Eflagellatae) may have originated multiple times.