6702 Smelowskia C.A. Mey.
Notes: Murray, Mulligan, and Elven: The classic study of northwestern North American Smelowskia is Drury and Rollins (1952). They accepted two species, S. calycina and S. (Melanidion) borealis, both with several varieties. Subsequently, Rollins (1993) treated the majority of the plants of Smelowskia in northwestern North America as varieties of S. calycina, a species described from the Altai. Velichkin (1974) rather treated the Beringian 'holophyllous' taxa as three species, all different from S. calycina and its several relatives in Siberia and central Asia by, e.g., caducous sepals, and also different from S. americana (Hook.) Rydb. One argument forwarded by Yurtsev (PAF proposal, comments) in support of Velichkin's approach was that the southern representatives, both in central Asia (e.g., S. calycina s. str.) and in the Rocky Mountains (S. americana), are diploid with 2n = 12, whereas the Beringian taxa have higher numbers of 2n = 18, 22, 24, and 32.
Velichkin's acceptance of the Beringian material as different at species level from both S. calycina and S. americana is largely supported by the molecular results of Warwick et al. (2003a) and Carlsen et al. (2010). His supposition of several species within this Beringian material is less well supported. Yurtsev's consideration of a consistent difference in ploidy levels is not supported: S. americana is reported with 2n = 22 (several counts; Mulligan and Packer, comment by Mulligan) from distinctly non-arctic Alberta, and the diploid number of 2n = 12 is known from arctic Beringian taxa, one count from western Alaska for S. spathulatifolia and several from Alaska and the Yukon Territory for S. media.
Warwick et al. (2003a) treated the arctic plants of the S. calycina group in the following way: they accepted S. alba and S. media (besides the non-arctic S. americana and S. calycina), whereas they included S. jurtzevii in S. porsildii (which they accepted) and S. spathulatifolia in S. americana. Except for the last-mentioned item, we agree with their treatment.
Carlsen et al. (2010) studied variation in microsatellites and DNA sequences, found distinctions among the temperate species in Asia and North America, and also found S. media to be distinct. They were unable to resolve the strictly Beringian group of S. jurtzevii, S. porsildii, and S. spathulatifolia. These molecular results agree with our morphological considerations. After comparing material (ALA, CAN, DAO, G and G-DC, LE, MHA, MW, O, S) from both Asia and North America, we agree that the Asian S. alba and S. bifurcata (aspleniifolia), the eastern Beringian S. media, and the Cordilleran S. americana deserve specific rank. We find it problematic to recognize more than one central Beringian species: S. porsildii (including S. jurtzevii and S. spathulatifolia).