A taxonomic and phytogeographical review of some arctic and alpine Senecio species

Abstract

PACKER, J. G. 1972. A taxonomic and phytogeographical review of some arctic and alpine Serlecio species. Can. J. Bot. 50: 507-518. A review is presented of the taxonomy of four arctic and (or) alpine species of Senecio, S . contermitzus Greenman, S . I~yperborealis Greenman, S . reseciolirrs Less., and S. cyrnbolarioides Buek. Of these, the first three have been recently claimed by one authority or another to have disjunct distributions between the Alaska-Yukon area and the Rocky Mountains. Investigations based on morphology (including that of the pollen) and cytology confirm the recognition of the four species and have furnished clear evidence for the recognition of a new species, S . ogotorukerrsis Packer, a description of which is provided. It isconcluded from the author's understanding of the taxonomy of these species that none has a disjunct distribution between the Alaska-Yukon area and the Rocky Mountains.PACKER, J. G. 1972. A taxonomic and phytogeographical review of some arctic and alpine Seriecio species.Can. J. Bot. 50: 507-518. L'auteur examine la taxonomie de quatre especes arctiques et (ou) alpines de Setlecio: S . cot~termitzrrs Greenman, S . hyperborealis Greenman, S . reserlifolirrs Less. et S. cymbnlarioides Buek. Parmi ces especes, les trois premieres ont une aire de distribution qui, d'apres certains auteurs rkents, presenterait une discontinuite entre la region de ]'Alaska-Yukon et les montagnes Rocheuses. Des recherches fondees sur la morphologie (y compris celle du pollen) et la cytologic ont confirm6 I'existence des quatre especes et ont clairement dtmontre I'existence d'une nouvelle espece, S. ogotorrrkeusis Packer, qui est dkrite. La conception de I'auteur sur la taxonomie de ces especes I'amtne a conclure que, dans leur distribution, aucune ne prtsente une discontinuite entre la region de ]'Alaska-Yukon et les montagnes Rocheuses.

An analysis of morphological variation in Senecio cymbalaria (Asteraceae)

“…In general our results support Packer's (1972) morphologically based arguments for recognizing the southern Rocky Mountain populations as a distinct species, S. contel-minus, and agree with the recent treatment of Senecio in British Columbia by Douglas (1982). This species can be consistently distinguished from the remainder of S. cymbalaria in characters of pubescence, pigmentation, basal leaf shape, and leaf serration.…”

“…In either case, this isolated group is now morphologically distinct, although it is not discretely different based on the characters used in this analysis. Cytological data suggest that the southern Rocky Mountain populations have uniformly high chromosome numbers (2n = 160+) (Packer 1972). Whether this chromosome number is unique within the S. cymbalaria complex is unclear at this time; however, the uniformity of the counts reported from this region supports the recognition of the populations as a distinct taxon.…”

“…Characters such as leaf thickness, head size, and pollen grain spines, although considered useful in separating S. conterrninus by Packer (1972), were not included in our analysis because of the difficulty in making reliable measurements from dried specimens. Because we wanted to emphasize differences in proportions and shapes, rather than size differences, many of the characters are ratios of measurements.…”

“…Barkley's views are similar to those of Cronquist (1 955), Ferris (1960), and Moss (1959). According to Packer (1972) Fernald (1924) rejected recognition of S. fernaldii, stating that he was "unable to find any stable characters by which S. fernaldii can be maintained as specifically distinct from S. resedifolius (= S. cymbalaria)". Senecio fernaldii is not recognized in any contemporary treatments o r floras.…”

“…Published counts for S. cymbalaria from the Altai region of the U.S.S.R. are 2n = 4 6 (Sokolovskaja and Strelkova 1938). Packer (1972) reported counts of 2n = 92 from Yukon, 2n = ca. 160+ from southern Alberta (six individuals) and 2n = 138 from Newfoundland (one individual).…”