Panarctic Flora

640801-02 The Dryas octopetala aggregate D. ajanensis, D. octopetala

Geography: Amphi-Atlantic (E) - European - Asian - amphi-Beringian.

Notes: Elven and Murray: The concept of Dryas octopetala is the major difference between the 'Hultén' and 'Russian' approaches. Hultén's D. octopetala with six subspecies contrasts with Yurtsev's (1997) three subsections (Dryas, Incisae, Punctatae) with nine species and seven additional subspecies. Yurtsev (1984c) reported several characters distinguishing the mainly European D. octopetala from the eastern Asian and amphi-Beringian D. ajanensis. We have found it problematic to apply this separation morphologically. However, it is supported by molecular data (AFLP: Skrede 2004, comments; Skrede et al. 2006) where the Beringian D. ajanensis subsp. beringensis and the European and northern Siberian D. octopetala were assigned to different main groups (besides D. drummondii). We therefore follow Yurtsev in his narrower circumscription of D. octopetala and also in accepting the distinction between D. octopetala and D. ajanensis. Our provisional (and non-molecular) aggregate then corresponds to Yurtsev's series Dryas with two species. It is characterized by, e.g., crenate-dentate leaves with feathery hairs but without glands.

Yurtsev's concept of D. ajanensis merges Hultén's subsp. tschonoskii with the Beringian parts of Hultén's subsp. octopetala, whereas the name D. ajanensis is almost absent from Hultén's treatments (and not assigned anywhere).

The discussions among the PAF collaborators have mainly concerned Yurtsev's concept of D. octopetala. Yurtsev excluded D. octopetala s. str. from the Arctic and rather assigned to D. octopetala subsp. subincisa all arctic plants from eastern Greenland across northern mainland Europe and Svalbard to Siberia, perhaps also some plants in the Russian Far East, Alaska, and Canada. The two main questions are then whether his division of non-Beringian D. octopetala into two subspecies was justified and whether there are one or two species of the aggregate in Beringia. Yurtsev (1984c) mapped D. octopetala subsp. subincisa east to approx. 105E in Taimyr and D. ajanensis subsp. beringensis from the Chukchi Peninsula west to approximately 175W in Chukotka. This leaves a gap of about 80 longitude. He assigned all plants in this gap to D. punctata subsp. punctata and D. incisa, both without feathery hairs. This pattern supports treatment as two taxa, perhaps species, but we are not convinced that it is real. We have collected and inspected many plants with the morphological features of D. octopetala/D. ajanensis (i.e., feathery hairs but no glands) in northern Yakutia (130E). For the variation within D. octopetala s. str., see below.

We base our decision on a combination of the morphological and geographical pattern and on the available molecular data. As they belong to two different major groups in the analysis of Skrede et al. (2006) and differ morphologically, we accept two species: D. octopetala and D. ajanensis. We restrict the range of D. octopetala compared with Yurtsev's PAF proposal and exclude it from Beringian Asia and North America, perhaps also from Greenland (see below).