Panarctic Flora

671611-14 The Cardamine digitata aggregate C. blaisdellii, C. digitata, C. "hyperborealis", C. microphylla

Geography: Asian (N) - amphi-Beringian - North American (NW).

Notes: Carlsen, Elven, M.H. Jørgensen, Murray, and Petrovsky: Molecular data support a monophyletic group of "core Cardaminella" including the Cardamine digitata aggregate, C. purpurea, C. sphenophylla, C. victoris, and some additional non-arctic species (Jørgensen et al. 2008; Carlsen et al. 2009). The closest relatives of the aggregate are found in western North America (some species) and eastern Asia (one species). The aggregate seems to have a Pacific origin.

Five species names have been in use more or less recently in the aggregate: C. microphylla, C. digitata, C. blaisdellii, C. hyperborea, and C. richardsonii. These five names are related to the four taxa entered for the Checklist in the following way:

Cardamine microphylla Adams 1817 was described from the Lena River estuary in northeastern Siberia and is documented from northern Siberia and West Chukotka. Molecular data and also morphology support a disjunct part range in northeastern Alaska, the northern Yukon Territory, and the northwestern mainland Northwest Territories (Jørgensen et al. 2008). These plants merged within the cluster of northern Asian C. microphylla and indicate that C. microphylla is disjunct amphi-Beringian. However, many authors have applied the name C. microphylla, erroneously according to our data, to East Chukotkan and western Alaskan plants which more recently are represented by the names C. hyperborea in Russian usage (non Schulz) and C. blaisdellii in North American usage. Cardamine blaisdellii seems to fill the gap in the disjunct range of C. microphylla.

Cardamine digitata Richardson 1823 was described from the mainland east of the Mackenzie River in northwestern Canada. The name is unambiguous as only one taxon of the aggregate occurs in that area. Trautvetter (1879) and Schulz (1903) misunderstood this plant (see comments below) but their var. oxyphylla of either C. digitata or C. hyperborea refers to C. digitata s. str.

Cardamine blaisdellii Eastw. 1902 was described from the Nome area on the Seward Peninsula, western Alaska, and was discussed by Murray and Kelso (1997).

Cardamine hyperborea O.E. Schulz 1903 was coined as a nomen novum for C. digitata Richardson which Schulz assumed to be later a homonym of C. digitata Lamarck 1786. However, Lamarck described his species as a Dentaria, not a Cardamine, and his name therefore does not invalidate Richardson's name. Cardamine hyperborea is therefore a synonym for and homotypic with the validly described C. digitata, as pointed out by Shetler (1961) and Rollins (1993) and confirmed by Egorova (in comment): "Cardamine hyperborea is a nomen superfluvum illegitimum for [C. digitata Richardson] according to Art. 52.1-52.2 of the St. Louis Code". Schulz (1903) erroneously applied the name C. hyperborea for the two species now known as C. microphylla and C. blaisdellii. He treated C. digitata in its original meaning (sensu Richardson) as a C. hyperborea var. oxyphylla. The more recent Russian usage of the name C. hyperborea, for a plant with broad leaf lobes different from both C. microphylla and C. digitata, is therefore also erroneous. The correct name for a part of these plants is C. blaisdellii.

Also Cardamine richardsonii Hultén 1945 was coined as a nomen novum for C. digitata Richardson, as Hultén, on the authority of Schulz, erroneously assumed that Richardson's name was predated by Lamarck's "digitata" and that the name C. hyperborea as applied by Schulz belonged to the broad-leaved plants. Hultén's name is therefore a superfluous, full synonym of C. digitata. Löve and Löve (1975a) followed Hultén.

In addition to C. digitata and C. blaisdellii, plants with an intermediate morphological expression are present in East Chukotka. Petrovsky suggested that these possibly were different from C. blaisdellii and fitting the more recent Russian usage of the name C. hyperborea. Molecular studies (microsatellites: Jørgensen et al. 2008) suggest that parts of Petrovsky's C. hyperborea belong to C. blaisdellii. Other parts are more problematic, see C. "hyperborealis" below.

Petrovsky: Löve and Löve (1975a) arbitrarily interpreted chromosome counts from the Russian publications by sorting them according to ploidy levels. Actually, these data belong to three different species: C. digitata, C. blaisdellii, and C. microphylla. All three species have tetraploid and hexaploid races, C. microphylla also higher numbers.