Circumpolar Arctic Floristic Provinces - Canadian Group
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Circumpolar Arctic Floristic Provinces - Canadian Group.
"In the northernmost parts, we have agreed to lump two regions initially recognized by Yurtsev into the one Ellesmere-North Greenland region, consisting of Axel Heiberg Island, Ellesmere Island, part of Devon Island, and the northern part of Greenland. This region is justified by a small element of endemic species, which might indicate some glacial refugia in the area. The more southern continental parts of Arctic Canada pose the main problems not yet solved. Yurtsev's proposal was to recognize fairly restricted regions in the west (North Alaska) and east (Baffin-Labrador). He then proposed to divide the remaining Arctic Canada into West Hudsonian and Central Canadian [subprovinces]. Canadian and West European participants in the debate proposed to extend those Atlantic and Beringian regions, both on the mainland and in the islands, as far as there are a significant Atlantic and Beringian elements in their floras. Then there would be room only for one Central Arctic Canada region." (From Elvebakk et al. 1999.)
- Central Canada sector
This sector is at present poorly defined. "The flora is markedly continental, with a clear influence from the adjacent 'Cordilleran-Beringian-Siberian' flora of the Alaskan province. There are also some floristic connections with the Siberian Arctic, e.g. Astragalus tomaczevii, Draba subcapitata, Oxytropis arctica s.s. as well as an interesting set of endemic species, including Parrya arctica, which forms a monotypic genus according to some Russian taxonomists. The northernmost part of the subprovince-belonging to [Subzone A] is much impoverished." (Modified from Yurtsev 1994.)
- West Hudsonian sector
"This sector is mainly characterized by the absence of differential species of the Baffin-Labrador [sector] and differential and western co-differential taxa of the Central Canadian subprovince. Overlapping distribution areas are shown by western (West American and Siberian-West-American) co-differential taxa; e.g. Cardamine digitata, Salix alaxensis, S. lanata ssp. richardsonii and Oxytropis arctobia, and eastern co-differential taxa: the amphi-Atlantic Cerastium alpinum, Diapensia Lapponica, Harrimanella hypnoides and Salix herbacea; and the East American Salix calcicola and S. planifolia. Two subendemics, Oxytropis bellii and O. hudsonica, occur." (From Yurtsev 1994.)
- Ellesmere–North Greenland sector
"This [sector] shows a continental Arctic to High Arctic type of flora. The main diagnostic features of the flora are negative: the absence of (1) amphi-Atlantic and other oceanic Arctic and Arctic-alpine species, (2) western co-differential taxa of the Central Canadian [sector] (e.g., Caltha arctica, Gentiana arctophila, Salix polaris and Senecio frigidus) and (3) legumes."
"Some floristic differences between the Canadian and Greenland parts of this sector are of minor importance, e.g., the presence of Carex membranacea, Hulteniella integrifolia and the endemic Puccinellia poacea on the Ellesmere and Axel Heiberg Islands, and Arenaria pseudofrigida, Dryas punctata and Juncus castaneus in North Greenland. The inner parts of the Axel Heiberg and Ellesmere Islands and the 'Dryas area' in Peary Land are arid and have a warmer summer. They are floristically connected to distant areas in Siberia and North America."
"Unlike the Arctic to High Arctic Ellesmere-North Greenland [sector], all other [Canadian sectors] show a zonal range from the Hypoarctic tundras (southern or northern) up to the Arctic ones, whereas the Baffin-Labrador province is situated mostly in the southern Baffin-Labrador [sector] with 'islets' of forest-tundra. Most parts of the Canada-Greenland [sector] were subjected to Pleistocene glaciations and subsequent isostatic sea transgressions. The southern island were covered by the Laurentide Ice Sheet. Parts of the westernmost Canadian Arctic archipelago were not glaciated and remained an area of continuous development of the Arctic flora, resulting in a local Central Canadian endemism."
"Other parts of the archipelago north of the Laurentide Ice Sheet, e.g. the Queen Elisabeth Islands, with flat or plateau relief, might have remained unglaciated and above sea level during certain intervals of the Late Pleistocene glaciation. This view is supported by the presence of the subendemic Taraxacum holmenianum, the only diploid species in the polyploidy section Arctica, and the isolated occurrence of some Beringian taxa, such as Acomastylis rossii and Saxifraga eschscholtzii." (From Yurtsev 1994.)