500721 Saxifraga cespitosa L.
- L., Sp. Pl.: 404 (1753). Lectotype (LINN): Europe. Herb. Linn. 575.57 (Webb 1950a: 222). - Muscaria cespitosa (L.) Haw., Saxifr. Enum.: 37 (1821).
Notes: Zhmylev: I consider Saxifraga cespitosa to be a complicated and poorly studied taxon where some entities have been named as species, but which the majority of botanists now regard as one polymorphic species with several poorly differentiated morphological races. Two races are proposed by me: a very widely distributed subsp. cespitosa and an amphi-Pacific subsp. monticola.
Elven: We follow Zhmylev's proposal but are in doubt whether the considerable variation can be represented as only two races. The majority of northwestern European and Russian authors have considered this species collectively. North American authors have, at least as late as Porsild and Cody (1980), recognized several races for their regions: (a) subsp. cespitosa in southern and western Greenland and Canada, comparatively southern (and amphi-Atlantic); (b) subsp. exaratioides as a more local race of the Hudson Bay area and northeastern Canada; (c) subsp. monticola as a Cordilleran race (i.e., not amphi-Beringian as proposed by Zhmylev); and (d) subsp. uniflora as a northern race in eastern, northern, and northwestern Greenland, Canada, and Alaska (and circumpolar). Böcher et al. (1978) recognized three subspecies for Greenland: subsp. cespitosa, subsp. uniflora, and an Atlantic subsp. laxiuscula.
The races recognized by the North Americans represent some reality, but the variation has not been attempted divided on taxa in a similar way in Europe or northern Asia, possibly except for Svalbard where Rønning (1996) recognized both S. uniflora and S. aurea (Hadac) Rønning, the latter characterized by yellow, half closed flowers with narrow petals. Such plants may differ in some genetic markers (Brochmann pers. comm.) and have their own ecology, mainly in snowbeds. However, similar plants occur also elsewhere and as populations, e.g., occasionally in both northern and southern Norway. Their status as a taxon is strongly doubted.
Also the northern Siberian plants look different when compared with European (and type) ones, as do most Beringian plants assigned to S. cespitosa. A circumpolar investigation combining morphology and molecular markers is needed. We can support the conclusion of Brouillet and Elvander (2009b): "It seems futile at this time to recognize any of the infraspecific taxa that have been described ... Expressions of all of the purported distinguishing characters overlap or have little apparent geographic or ecologic correlation".