Flora of the Canadian Arctic Archipelago
Asteraceae (Compositae), Daisy family.
Published in Bot. Not. 128: 520. 1976.
Synonymy. Senecio hyperborealis Greenm., Ann. Missouri Bot. Gard. 1: 264. 1914.
Tephroseris hyperborealis (Greenm.) Barkalov, Sosud. Rast. Sov. Danego Vostoka 6: 238. 1992.
Vegetative morphology. Plants 5–10(–25) cm high (taller plants on continental North America); perennial herbs. Only fibrous roots present. Ground level or underground stems vertical. Caudex present (with short branching base). Aerial stems erect. Leaves present; mainly basal; alternate; marcescent. Petioles present; 5–15(–40) mm long; hairy. Petiole hairs longer than the diameter of the petiole; appressed, or spreading; floccose. Leaf blades simple. Leaf blade bases truncate, or obtuse. Blades 5–35(–70) mm long (Leaves larger in some plants from continental North America), 4–30 mm wide, spreading, lyrate, flat, veins pinnate. Blade adaxial surface glabrous. Blade abaxial surface glabrous. Blades lobed. Blade margins glabrous; degree of incision 0–85% (very variable); apices obtuse, or rounded.
Reproductive morphology. Flowering stems with leaves (usually), or without leaves (small plants). Inflorescences solitary heads (arctic island specimens), or of several flowering heads (with 2–4 heads, specimens from continental North America); globose or sub-globose, or ellipsoid. Flowering heads with disc and ray florets. Pedicels subtending flowering heads; with non-glandular hairs (if applicable). Involucral bracts present. Number of rows 1. Outer involucral bracts mostly green (or yellowish with limited red tinges); lying adjacent to the flowers; lanceolate; 4–5 mm high; 2–3 mm wide (tending to reflex with age or in pressing); glabrous. Inner involucral bracts linear, or lanceolate. Flowers radially symmetrical (actinomorphic) (disc florets), or bilaterally symmetrical (zygomorphic) (ray florets); unisexual (ray florets), or bisexual (disc florets). Sepals represented by a pappus. Pappus with a single row of hairs. Ray florets pappus 5–6 mm long. Disc florets pappus 5–6 mm long. Petals conventional; fused; 5; yellow. Corolla tubular, or funnel-form (disc florets), or flat, strap-like (ray florets); 3-lobed (indistinct ray florets), or 5-lobed (disc florets). Stamens 5. Anthers 1.5–2.5 mm long. Ovary inferior (receptacle surface densely hairy); carpels 2; syncarpous. Styles 1. Stigmas per ovary 2. Placentation basal. Ovules per ovary 1. Fruit sessile; with calyx persisting; dry; cypselas; brown (pale); 1–2 mm long; 0.5–1 mm wide; hairy (with fine fur-like hairs); surface appearing veinless; indehiscent. Seeds 1.
Chromosome information. 2n = 46–48.
2n (2x?) = 46–48. Packer (1972, western Canada, 2n = 46); Yurtsev and Zhukova (1972, northeastern Asia, 2n = 48).
Ploidy levels recorded 2x(?).
Ecology and habitat. Substrates: slopes, cliffs; dry; calcareous.
North American distribution. Alaska, Yukon, Northwest Territories Islands, continental Northwest Territories. Range in the Canadian Arctic Archipelago limited. Rare. Low Arctic. Arctic islands: Banks.
Northern hemisphere distribution. Amphi-Beringian. Wrangel Island, East Chukotka, West Alaska, North Alaska Yukon, Central Canada.
General notes. When Löve and Löve (1976) erected the genus Packera, they indicated that this is mainly a North and South American genus with a few representatives in Asia. It comprises the groups Aurei, Lobati, and Tomentosia of the collective genus Senecio. Taxa in Packera stand apart from other divisions of the collective aggregate by having long rhizomes, and if pubescence is present it is a tomentum of more or less arachnoid and never of long jointed hairs that persist as flocculent tufts. Its morphological and geographical distinctions are enhanced by its basic chromosome number, x = 23, which differs from that of Senecio s.s., x = 10, and Tephroseris (Richb.) Richb., x = 8.
Barkley (1999), discussing the segregates of Senecio that are recognised in the Flora of North America treatment (Barkley 2006), including Packera (Trock 2006) stated that the notions leading to these narrower generic concepts are noted in Bremer (1994) and in several papers that were presented at the Compositae Conference at Kew in the summer of 1994 (Hind and Beentje 1996). He provided a synoptic key, stating that nobody doubts the biological significance of the first couplet, but the characters used are impractical for routine plant identification. The first couplet separates the Tussilagininae, which includes Tephroseris, and the Senecioninae, which includes Packera and Senecio.
1. Stigmatic areas confluent on adaxial faces of style branches; anther collars cylindrical and cells not inflated; mostly n = 30, or polyploidy/dysploid derivatives ... Tussilagininae
1. Stigmatic areas marginal and distinct on distal, adaxial faces of style branches; anther collars swollen with basal cells inflated; n = (10) 20, or 22–23, or polyploidy derivatives (rarely genus Pericallis) ... Senecioninae.
Barkley (1999) recognised the genus Packera as having erect free standing plants; stems arising singly or clustered from a taproot, caudex, or rhizome and with abundant, thin branching fibrous roots; principal leaves in a basal cluster with blades not both palmately veined and with expanded-clasping petiole bases; cauline leaves progressively reduced distally; corollas mostly yellow n = 22 or 23, or polyploidy derivatives.
Barkley (1999) indicated that the genus consists of about 60 species centred in the western temperate half of North America but extending into southern Mexico and into the Arctic. Two arctic-alpine species extend into northern Siberia and central Asia. The group has been known as the aureoid complex of Senecio s.l., and although its members are superficially similar to many species of Senecio it forms a distinct lineage. Intergradation among Packera species is well known (Barkley 1988), but there is no morphological intergradation or putative hybridisation between any Packera and any species of Senecio s.s., or segregate of Senecio. The pollen grains of Packera have a helianthoid ultrastructure, rather than the senecionoid type (Bain and Walker 1995). An ITS-based phylogeny has been estimated for Packera by Bain and Jansen (1995).
Illustrations. • Habitat: Continental NWT. Centre, plant with single yellow flowering heads and characteristically lyrate leaves, growing in exposed sand. N.W.T., Tuktoyaktuk. Aiken and Brysting 2001. • Habitat: Banks Island. Plant growing between the markers. It has yellow flowering heads in bud and lyrate leaves. N.W.T., Banks Island, Aulavik National Park. Aiken 99–038. CAN. Scale bar in cm. • Close-up of capitulum. Left, previous season's capitulum with reflexed involucral bracts. Right, capitulum with a few ray florets expanding. Note that at this stage the strap-like petals are rolled and the numerous disc flowers are in bud. Aiken 99–038. CAN. • Close-up of flowering head. Flowering head approximately 1.5 cm in diameter, with expanded ray florets that have stigmas protruding at the base and disc florets that are in bud. Aiken 99–053. CAN. Scale bar in cm. • Closer-up of flowering head. Note ray florets with three lobes at the tips of some petals and yellow strap-like stigmas. One disc floret has opened and has five acute petals and two strap-like stigmas. Aiken 99–053. CAN. • Arctic Island Distribution.
This publication is available on the internet (posted May 2011) and on CD-ROM (published in 2007). These versions are identical in content, except that the errata page for CD-ROM is accessible on the main index page of the web version.
Recommended citation for the web-based version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. NRC Research Press, National Research Council of Canada, Ottawa. http://nature.ca/aaflora/data, accessed on DATE.
Recommended citation for the CD-ROM version of this publication: Aiken, S.G., Dallwitz, M.J., Consaul, L.L., McJannet, C.L., Boles, R.L., Argus, G.W., Gillett, J.M., Scott, P.J., Elven, R., LeBlanc, M.C., Gillespie, L.J., Brysting, A.K., Solstad, H., and Harris, J.G. 2007. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. [CD-ROM] NRC Research Press, National Research Council of Canada, Ottawa..