Relationships among pansies (Viola section Melanium) investigated using ITS and ISSR markers

Abstract

Sequences of the nuclear region ITS and the variable molecular markers ISSR were used to estimate the phylogeny of the section Melanium of the genus Viola. We confirm that the so-called pansies form a derived and monophyletic group. Two floral characters, the upturned side petals and the large size of pollen grains appear to be synapomorphies in Melanium. The Melanium species are very closely related, as shown by the reduced genetic variation compared to the other sections of Viola. Our analyses suggest x = 5 or x = 7 as the possible base chromosome number of the section Melanium. Polyploidy and hybridization would have played an important role in the evolutionary history of this clade resulting in a wide range of chromosome number. The low genetic differentiation and the complex cytological evolution suggest that diversification in Melanium is the result of a reticulate evolution and rapid radiation in Europe and Northern Africa.