Diapensia lapponica L. subsp. lapponica
Diapensia.
Diapensiaceae, Diapensia family.
Sp. Pl. 141. 1973.
Diapensia lapponica L. var. lapponica
Diapensia
lapponica var. genuina E. Busch
Diapensia lapponica var.
rosea Hultén
Vegetative morphology. Plants shrubs (small plants easily misinterpreted as herbs); dwarf shrubs; 1–5(–8) cm high; forming firm, hemispherical tussocks of stems with densely imbricate, evergreen, yellow-green usually curved, narrowly spatulate leaves. Taproot present. Ground-level or under-ground stems horizontal; compact, or elongate (occasionally, as when a plant is growing under a rock and sends a stem underneath which develops small cushion at the tip). Aerial stems erect (branching beneath the recent season's leaves in older tussocks with an accumulation of duff amongst the branches); glabrous. Leaves whorled (in dense ascending, compact whorls); simple (yellowish green in upper portion, pale at the base in summer; dark burgundy in winter); evergreen. Petioles absent. Blades 5–15(–20) mm long; 0.5–3 mm wide. Blades leathery; spatulate (narrowly); strongly keeled; appearing single-veined. Blades adaxial surface shiny. Blade margins entire; with glandular hairs. Leaf apices acute, or obtuse.
Reproductive morphology. Flowering stems absent. Flowering stems without leaves (The illustration in Porsild (1957) and Porsild and Cody, (1980) show leaves on the scape, but these have not been observed in nature; Peter Scott, personal communication 1999); glabrous. Flowers solitary (or 2–3). Involucral bracts present. Outer involucral bracts blade surface flat. Flowers medium-sized, 5–15 mm in diameter or length. Calyx sepals 5; free. Calyx green (yellowish or pinkish); glabrous. Petals fused (for half their length; corolla appearing deeply lobed); 5; white (or cream or rose, or light pink petals are known for this species from Newfoundland and for subsp. obovata from Alaska and Japan). Corolla rotate, or cup-like. Stamens 5; fused to the corolla (between each petal). Gynoecia superior. Carpels syncarpous. Styles 1. Placentation axile. Ovules many approx. 240. Fruit with calyx persisting; dry; a capsule; ovoid; dehiscent. Fruit 2–3 mm long; 1–2 mm wide; brown, or red (pale pinkish or yellowish). Seeds 27–128; 0.7–1.1 mm long (tetrahedral in shape); brown (pale cream under a conspicuous tan brown reticulation on the surfaces); with surfaces ridged (seedlings rarely seen).
Chromosome information. 2n = 12. Samuelsson (1913 northern Europe); Hagerup (1928 Greenland?); Baldwin (1939); Sørensen and Westergaard in Löve and Löve (1948 Greenland); Löve and Löve (1956b Iceland, 1966b northeast USA, 1982a central Canada); Jørgensen et al. (1958 Greenland); Sokolovskaya and Strelkova (1960, 1962); Dalgaard (1989 western Greenland). Supposed basic chromosome number of family 2x. Ploidy levels recorded 2x.
Distribution. Northern hemisphere distribution: amphi-Atlantic; Greenland, St. Pierre and Miquelon, Canada, United States, Eurasia. Continental Northwest Territories, Nunavut Islands, Continental Nunavut, Northern Québec. Low arctic. Range in the Canadian Arctic Archipelago limited. Uncommon. Arctic Islands: Baffin, Ellesmere, Southampton.
Ecology and habitat. Substrates: tundra, slopes, ridges (the streamlined heat and nutrient trapping growth form, allows this species to grow in exposed arctic-alpine habitats); imperfectly drained moist areas (less commonly), or dry; acidic (often found on Precambrian materials, rocky ledges or gravel); rocks, gravel, silt (run off banks); with low organic content. Habitats: A plant of dry exposed habitats, D. lapponica has been reported with ericaceous shrubs in the Arctic Islands. Flowering in June-July. Pollinated by members of Diptera.
Taxon as an environmental indicator. Chionophobic, that is, it does not like snow so tends to grow in wind-swept habitats.
Economic uses. Diapensia is not of economic importance as yet. However, the oils in its tissues may some day be of value (Bliss 1962). Diapensia is a very desirable garden plant, but attempts at cultivation in lowland locations usually fail.
Notes. In Newfoundland and New England, plants have been found to
bloom in June or August. It is thought that this phenology produced seeds in the
autumn which are less likely to be parasitized by fungi. Diapensia
lapponica has subspecies lapponica and obovata which have
distinct distributions. Subspecies lapponica is found in eastern North
America from New England to Ellesmere Island and in Greenland, Iceland,
Scotland, Scandinavia and the western Soviet arctic and sub-arctic. Subspecies
obovata is found in eastern arctic and sub-arctic Siberia, Korea, Japan,
Aleutian Islands, Alaska, and the Yukon. Subspecies obovata has obovate
leaves while those of subsp. lapponica are narrowly spathulate.
Subspecies obovata has a more 'sprawling' growth form, not usually
forming distinct small tussocks. Leaf length/width ratios are, subsp.
lapponica 2–2.5, susbp. obovata 2.75–2.8, Scott (1983);
Day and Scott (1981) Scott and Day (1983; Day and Scott (1984).
Roach D, A.
and Marchand, (1980), in a study of reproductive strategies of pioneering alpine
species seed production dispersal and germination found that D. lapponica
lacked the above characteristics and was much less opportunistic in reproductive
behavior than other species studied.
Illustrations. • Plant habitat. Cushion plants with white flowers growing beside the bank of a run-off channel with bilberry and sedge. Nunavut, Baffin Island, near Mt Joy. Aiken and Ilses, 2002. No voucher. • Close-up of flowers. Flowers with five petals and stamens alternate with the petals. Nunavut, Baffin Island, Iqaluit, July 19, 1982, J.M. Gillett 18957, CAN. • Close-up of plant. Plants in flower and beginning to set fruit. Nunavut, Baffin Island, Soper River Valley, Mt. Joy. Scale bar in cm. Aiken and Ilses, 2002. No Voucher. • Plant in bud.. Cushion plants barely 2 cm high coming into flower. Nunavut, Baffin Island, Iqaluit. Aiken and Mallory, 02–004. CAN. • Close-up of buds. Buds with itwo layers of involucral bracts; the outer green, shorter and narrower, the inner twic as wide and flat. Inside a pale green calyx. Nunavut, Baffin Island, Iqaluit. Aiken and Mallory, 02–004. CAN. • Side view of flower. Flower with green calyx much shorter than the petals, five white petals that are fused at the base, anthers attached to the petals and alternate with them and a central stigma. Aiken and Mallory, 02–004. CAN. • Close-up of flower. Flower with five fused petals and five anthers that are attached to the petals and borne alternate with them. Note anther and open towards the centre of the flower and there is a single capitate stigma. Nunavut, Baffin Island, Soper River Valley. Aiken and Ilses, 2002. No Voucher. • Side view of developing fruit. -5. • Surface view of fruits.. Centre: dark brown, dehisced capsules of previous season's fruits that have split to show axile placentation. Left, ripening current season's fruit. Nunavut, Baffin Island, Iqaluit. Aiken and Mallory. No Voucher. • Close-up of leaves in fall. Plants with orange green leaves, that are compact, ascending and whorled. Nunavut, Baffin Island, Iqaluit, July 19, 1982, J.M. Gillett 18957. • Arctic Island distribution.
Cite this publication as: ‘S.G. Aiken, M.J. Dallwitz, L.L. Consaul, C.L. McJannet, L.J. Gillespie, R.L. Boles, G.W. Argus, J.M. Gillett, P.J. Scott, R. Elven, M.C. LeBlanc, A.K. Brysting and H. Solstad. 1999 onwards. Flora of the Canadian Arctic Archipelago: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 29th April 2003. http://www.mun.ca/biology/delta/arcticf/’. Dallwitz (1980) and Dallwitz, Paine and Zurcher (1993, 1995, 2000) should also be cited (see References).
