862403 Petasites frigidus (L.) Fr.
- Fr., Summa Veg. Scand. 1: 182 (1845). - Tussilago frigida L., Sp. Pl.: 865 (1753). Lectotype (LINN): Sweden: "Lapland". Herb. Linn. 995.17 "A Lapponia edduxi" (Toman 1972: 389). - Nardosmia frigida (L.) Hook., Fl. Bor.-Amer. 1: 307 (1833). - Nardosmia angulosa Cass. in F. Cuvier, Dict. Sci. Nat., ed. 2, 34: 188 (1825). Illegitime nomen novum for Tussilago frigida.
2n=
(1) 60 (6x). - Alaska, Canada (W). - Taylor and Brockman (1966); Mulligan (1969).
(2) 90 (9x). - Alaska. - Packer and McPherson (1974).
Geography: Circumboreal-polar.
Notes: Petasites frigidus is fairly monomorphic in arctic Europe and Siberia east to the Kolyma River but more polymorphic in Beringian Asia and in North America. The recorded variation is, however, mainly in shape, dissection, and pubescence of the leaves. Intermediates between the proposed taxa are reported to be frequent. Korobkov (PAF proposal) accepted four species: P. frigidus s. str., P. hyperboreus Rydb., P. palmatus (Aiton) A. Gray, and P. arcticus A.E. Porsild. Cody (1994, 1996) accepted these as four races of P. frigidus: subspp. frigidus, nivalis (= hyperboreus), palmatus, and arcticus. Other North American botanists have been reluctant to accept more than two races, e.g., Cherniawsky and Bayer (1998a, 1998b, 1998c) and Bayer et al. (2006) who included subsp. nivalis in subsp. frigidus and subsp. arcticus in subsp. palmatus.
The geographical pattern of the morphological variation is comparatively clear. Subspecies frigidus s. str. with dentate to shallowly lobed leaves predominates in Europe and Siberia but is frequent also in northeastern Asia and in northwestern North America south to northern British Columbia and east to across the Mackenzie River. Subspecies palmatus s. str. with very deeply lobed leaves predominates across most of North America but seems to have its western limit in the southern Yukon Territory (i.e., nearly absent from all of Beringia). Subspecies nivalis is intermediate between the two above in leaf dissection and also occupies an intermediate range in northwestern North America south to southern British Columbia and Alberta and in northeastern Asia at least in Chukotka. These three have similar site preferences. This morphological and geographical pattern can be explained in at least two ways: (1) Separate survival and differentiation during the last or several glaciations in three regions: non-Beringian Eurasia (subsp. frigidus s. str.), Beringia (subsp. nivalis), and non-Beringian North America (subsp. palmatus s. str.). Subsequent secondary meeting due to efficient wind dispersal and introgression due to insufficient reproductive barriers. This could justify treatment as three taxa. (2) The same, but survival only in Eurasia-Beringia (subsp. frigidus s. str.) and non-Beringian North America (subsp. palmatus), and subsequent introgression resulting in subsp. nivalis in Beringia. This would rather justify two taxa and their hybrid. However, subsp. nivalis today mainly occurs outside the range of subsp. palmatus s. str. We accept them as three subspecies. For the fourth entity, see the fourth subspecies below.
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Source: CarolSpears at Wikispecies
Higher Taxa
- Petasites [8624,genus]