Notes on Viola riviniana

Viola riviniana Reichenb. var. (Violaceae) (Finland, Lohja, Maksjoki, 1987). – Photo: Mauri Korhonen. – I have noticed, among other variability, this kind of deviating plants of this violet in a few places in southernmost Finland. They appear intermediate between V. reichenbachiana Jordan ex Boreau and V. riviniana in some characters but the stipules are of a kind of their own. The exceptional chromosome number 2n = 30 was obtained from all four stands with this kind of violets that were studied cytologically (e.g. from a plant adjacent to the photographed one). The normal number in V. riviniana is 2n = 40 (tetraploid) and in V. reichenbachiana 2n = 20 (diploid). The deviating chromosome number would thus suggest a triploid hybrid between the species mentioned. However, (i) V. reichenbachiana does not occur in the mainland of Finland, (ii) the pollen, and (iii) the seeds of those voucher plants that were studied are normally developed. The 2n = 30 genome may actually be paleopolyploid and represent the hexaploid level, which would indicate the basic number is x = 5 instead of x = 10 as generally considered.

Literature: Harmaja, H. 2003: A deviating cytotype of Viola riviniana from Finland. - Ann. Bot. Fennici 40: 395-400.