Panarctic Flora


570110-11 The Viola palustris aggregate V. epipsila, V. palustris

Geography: Circumboreal-polar.

Notes: This aggregate has been investigated fairy extensively by Sorsa (1965, Finland), Brandrud and Borgen (1986, southern Norway), and Sordsa (1968, North America), by combining morphology and cytology. The prevalent western European and North American view is that it consists of two species. Viola palustris is octoploid (2n = 48), comparatively little varied in an arctic context, and broadly amphi-Atlantic. Viola epipsila is tetraploid (2n = 24) and more varied. The two species are largely sympatric, both in northern Europe and in eastern North America, with different but overlapping ecological demands. Viola palustris prefers oligotrophic sites, often bogs, whereas V. epipsila prefers mesotrophic to eutrophic fens and swamps. They hybridize frequently where they meet in some areas (e.g., Finland and southern Norway). The hybrids are mostly hexaploid (2n = 36) but several numbers between ca. 20 and 48 have been reported. Some good seed-production is observed but the majority of morphologically intermediate plants are seed-sterile. They may, however, form large clones due to extensive rhizomes. In spite of the hybridization their integrity as two species is not compromised.

Higher Taxa