Panarctic Flora


361210 Ranunculus subrigidus W.B. Drew


Wrangel Island: Scattered
Western Alaska: Rare
Northern Alaska - Yukon: Rare
Central Canada: Rare
Hudson Bay - Labrador: Rare
Ellesmere Island: Rare
Western Greenland: Rare
Northern arctic Tundra: Rare
Mid Arctic Tundra: Rare
Southern Arcti Tundra: Scattered
Shrub Tundra: Scattered
Bordering boreal or alpine areas: Scattered

2n= 16 (2x). - Canada (Manitoba). - Löve and Solbrig (1964a); Löve and Ritchie (1966); Löve and Löve (1982a).

Geography: Amphi-Beringian (E) - North American (N): RFE ALA CAN GRL.

Notes: Whittemore (1997) stated that: "The Eurasian species Ranunculus circinatus Sibthorp has been reported from North America. These reports are based on specimens of R. aquatilis var. diffusus". We emphatically disagree. There is a clear distinction in morphology and most probably also in ploidy levels between two taxon pairs in the northern North American material. One of them corresponds to the diploid R. circinatus + the diploid R. subrigidus, the other to the tetraploid and hexaploid R. trichophyllus + the tetraploid R. confervoides. We have found no way to separate American and Eurasian material of R. circinatus.

When Alaskan and northern Canadian material (ALA, CAN) was revised in 2009, it divided into five categories: (1) a mainly coastal R. aquatilis (see map in Whittemore 1997 for var. aquatilis); (2) a widespread, mainly temperate-boreal R. trichophyllus; (3) an arctic-subarctic R. confervoides morphologically inseparable from Eurasian plants; (4) an interior and northern plant deviating from both the previous ones in, e.g., very short-stalked leaves with stiff lobes making the outline of the leaves around the stems circular ("circinatus"), conforming to R. subrigidus as described by Drew (1936); and (5) a more southern, coarser counterpart of (4) but with the same very short-petiolate leaves, conforming to R. circinatus. This last-mentioned plant co-occurs with its assumed close relative, R. subrigidus, in some Canadian localities (e.g., in the Kingston area on Lake Ontario and in the Thunder Bay area on Lake Superior) without observed transitions in the Canadian material. It may reach the Arctic and is entered below.

Ranunculus subrigidus is mainly non-arctic in Alaska and the Yukon Territory but is vouchered (ALA) to reach the Arctic in a few coastal localities in northwestern (Point Hope) and northern Alaska and from at least two coastal localities on the Yukon side of the border. It is the most frequent species of the Batrachium group in non-Beringian arctic Canada north to Ellesmere Island and it occurs in several localities in northwestern and northern Greenland (CAN). We assume that R. subrigidus is the major plant of interior Alaska and northern Canada, intersparsed between the two American 'corners' of the range of R. confervoides (mainly Eurasian but extending east to Alaska and west to Greenland and northeastern Canada). Surprisingly, the few vouchers (O) seem from the Russian Far East Wrangel Island also conform to R. subrigidus which then becomes amphi-Beringian. The three species that reach the Arctic in Alaska, Canada, and Greenland are largely allopatric and no obvious hybrids were found in the ALA or CAN material (but perhaps due to predominant inbreeding). Ranunculus subrigidus shares several characters with and seems to be most closely related to R. circinatus but the lack of intermediates, even in sympatric situations, supports two species.

At least the majority of North American chromosome counts assigned to R. subrigidus are diploid as are counts of European R. circinatus s. str., whereas the majority of counts assigned both to R. confervoides and to northern R. trichophyllus are tetraploid or higher.

Elven and Aiken: We assume that the name R. codyanus belongs to R. subrigidus as this is the only species of sect. Batrachium known from its type area of Southampton Island (only material in CAN inspected).

Higher Taxa