Astragalus alpinus L. var. alpinus

Authors

Rupert C. Barneby

Authority

Barneby, Rupert C. 1964. Atlas of North American Astragalus. Mem. New York Bot. Gard. 13(1): 1-596.

Family

Fabaceae

Scientific Name

Astragalus alpinus L. var. alpinus

Type

"Habitat in Alpibus Lapponicis, Helveticis."—Holotypus labeled "Astragalus alpinus. Lapp.," LINN!

Synonyms

Astragalus alpinus L., Phaca minima All., Phaca astragalina DC., , Tragacantha alpina (L.) Kuntze, Astragalus astragalinus (DC.) E.Sheld., Astragalus phacinus E.H.L.Krause, Tium alpinum (L.) Rydb., , Atelophragma alpinum (L.) Rydb., , Astragalus arcticus Bunge, Phaca arctica (Bunge) Gand., , , , , Astragalus alpestris Bubani, Phaca astragalina f. occidentalis Gand., , Astragalus andinus M.E.Jones, Astragalus alpinus var. parvulus J.Rousseau, Astragalus alpinus f. parvulus Rousseau, Astragalus alpinus subsp. alaskanus Hultén, Astragalus alpinus var. alaskanus (Hultén) Lepage, Astragalus alpinus f. lepageanus J.Rousseau ex Lepage

Description

Variety Description - Habit of the species, usually low, the stem mostly 1-15 (25) cm. long above ground; racemes usually compact, sometimes loose in age, the axis 0.5-4 (7) cm. long in fruit; calyx 3.2-6.6 mm. long, the tube 2.2-4 mm. long, (1.3) 2-3.7 mm. is diameter, the teeth 0.9-2.8 (3) mm. long; banner (6.2) 7.4-13.6 (14.8) mm. long, (3.8) 4.6-8 (8.8) mm. wide; wings 7.1-11.6 (13.1) mm. long, 1.6 mm. shorter to 1.6 mm. longer than the keel, the claws 2.2-4.7 mm., the blades 5-10.5 mm. long, 1.2-3.4 (3.7) mm. wide; keel 0.5 mm. longer to 2.4 mm. shorter than the banner, (7) 7.6-12.2 (12.7) mm. long, the claws (2.6) 2.8-5 (5.3) mm., the blades 5.1-8.7 (9) mm. long, (2.1) 2.5-4 mm. wide; stipe of the pod 1.4-3 mm. long, the body (6) 7-14 mm. long, 2.5-4.2 mm. in diameter, straight or gently incurved, villosulous with black or fuscous, often mixed with some (or many, exceptionally all) white hairs up to (0.4) 0.45-0.8 mm. long (very exceptionally calyx and pod glabrous).

Distribution and Ecology - Arctic and subarctic shores, lake and river banks, moist (but often summer-dry) meadows, turfy hillsides, and talus, in mountain pine forests, aspen groves, and about willow or alder thickets along streams, from near sea level northward up to 11,500 feet in the Colorado Rocky Mountains, without apparent rock preference but perhaps most abundant on limestone, widely dispersed from Alaska to Baffin Island, south to Labrador and extreme northern Newfoundland, James Bay in Ontario, northern Wisconsin, southern Manitoba, and along the Rocky Mountains and their piedmont hills to the Black Hills of South Dakota, northern New Mexico, western Wyoming, northeastern Nevada, the Wallowa Mountains in northeastern Oregon and the Okanogan Highland in northeastern Washington; in the Old World circumpolar (excepting Greenland, where reportedly introduced sparingly) from Scotland and Scandinavia to Kamtchatka, south to the Pyrenees, Alps, Carpathians, Altai, Tian Shan, and northern Kurile Islands.—Map (in America) No. 2— Mid-April to August (September), flowering soon after the spring thaw.

Discussion

The Austrian botanist Nicholas Jacquin (Collectanea 1: 323. 1786) neatly described the alpine milk-vetch as "gratissimus semper, et quia natura tenellus et quia adspectu decorus"; it is indeed an ever delightful, pretty but unassuming plant which speaks to the plant geographer of high, cool, and northern places. Wherever one may come upon it in its extensive range over arctic tundra and down through the mountains of the Northern Hemisphere, he will recognize the alpine milk-vetch by its slender, freely branching subterranean caudex, connate stipules, nodding flowers of characteristic shape, and by the pendulous, stipitate, trigonous but dorsally grooved pod pubescent nearly always with mixed black and white hairs. Typical var. alpinus is so well and widely known that it has seemed superfluous to cite representative material which may be found in plenty in all the larger herbaria of Europe and North America. In America the alpine milk-vetch is often sympatric and sometimes confused with forms of A. Robbinsii, a species similar in coloring and choice of habitat but easily distinguished by its superficial and determinate root-crown at the level of the soil, large, veiny, lower stipules, and a pod which is sometimes trigonous but only flattened and not sulcate dorsally. Care must also be taken to discriminate between A. alpinus and two dwarf species of Oxytropis, in Europe O. lapponica (Wahlenb.) Gay and in America O. deflexa var. foliolosa (Hook.) Barneby, which are not only similar in superficial appearance but not uncommonly found growing with it. The beaked keel, of course, distinguishes Oxytropis as a genus, and O. deflexa differs further by its free stipules and pod semibilocular by intrusion of a funicular flange and not by a true septum.

The alpine milk-vetch, in spite of its immense range, is not a highly variable species. The foliage is commonly green and thinly pubescent, but may be canescently hirsutulous, a phase known from scattered stations in America from Colorado to the Yukon Valley. The variation in stature and in the relative proportions of the petals has been analyzed from the point of view of the Alaskan flora by Hulten, who proposed for the relatively rank-growing, perhaps polyploid plant of the far Northwest (and probably of the Rocky Mountains) a subsp. alaskanus differing from subsp. alpinus in its elongate raceme of flowers with keel shorter than rather than equaling the banner and with narrow wings. However even in the Alps of Europe the wings of A. alpinus may vary from 1.4 to 3.4 mm. in width, with a variation of over 1 mm. recorded from plants mounted as parts of one collection, and this feature clearly has no systematic significance of itself. In Europe also the banner varies from at least 0.5 mm. shorter to 1 mm. longer than the keel. In the Rocky Mountains an elongate raceme, common in America but found only rarely in Europe, is not correlated with a keel short in proportion to the banner, nor with narrow wings. Not only are there short and long (more or less than 4 cm.) racemes in the same population, but the wings vary in the longer type from 0.8-3.2 mm. in width and the keel varies in the same group of plants from 0-2 mm. shorter than the banner. In North America, northward along the Cordillera from western Wyoming, A. alpinus is common in the timber belt and quite variable in stature and length of the racemes. Plants luxuriating in moist soil along brooks overhung with thickets of willow and shrubby cinquefoil, or on gravel bars of mountains torrents, as also in drier soils of lodgepole pine or aspen forest, tend to be drawn out, broad-leaved, and loosely flowered. But wherever a population of this sort, which corresponds closely to subsp. alaskanus Hult., passes directly and continuously out of moist shade onto a dry turfy bank or sunny exposure, the more compact growth-habit generally associated with the European plant is immediately regained. The subsp. alaskanus seems to be based on an arbitrarily selected series of relatively tall and lush specimens which even in Alaska and Yukon (cf. Hulten, 1944, maps 813, 813a) lack the geographic segregation which is normally expected of a subspecies.

A second variant of A. alpinus, possibly of greater racial importance since it is confined to the highest latitudes around the pole, has been described as A. arcticus Bge. It was maintained by Gontscharov as a distinct species under the epithet subpolaris, and recognized by Hulten (1944, 1. c.) as a subspecies coordinate with subsp. alaskanus. Bunge distinguished it from A. alpinus because of its regularly graduated, more richly colored petals, supposedly correlated with a more robust habit of growth. Gontscharov (op. cit. 40, in clave) brought out a further contrast between a fully bilocular pod in A. alpinus and a semibilocular one in A. subpolaris. About forty collections (over thirty from America) have been seen which would be referred to A. subpolaris because the wings surpass the keel in length. By no means all of these have bright purple flowers, and at least in America a flower of this type is not correlated with a relatively narrow septum. In Alaska the plants most closely resembling A. arcticus of Novaya Zemlya and northern Lapland are found chiefly along the north coast eastward from Behring Strait, but technically inseparable forms occur in the interior up to 3500 feet elevation. Hulten’s map (1944, no. 813b) shows correctly that the subsp. arcticus and alpinus are sympatric even at their northernmost limits, but leaves out the many puzzling specimens which fail to satisfy the criteria of proportions and coloring of the petals and cannot be considered typical of either subspecies. Such plants as Coville & Kearney 744 (US) with ample, brightly colored flowers but wings shorter than the keel, or A. E. Miller in 1919 (US) with small, pale flowers and wings longer than the keel, are real obstacles to recognition of distinct subspecies in Alaska. Hulten (1. c.) cites subsp. arcticus as extending east to Baffin and Labrador, but I have seen no material of the extreme type from east of Hudson Strait (A. P. Low 22,863, NY). Specimens near A. arcticus as ideally conceived have been collected as far south as Thunder Bay District, Ontario (Taylor & al. 679, GH), and these are particularly suggestive of an individual, independent variant not genetically linked to the arctic type. The differential characters are quite feebly correlated, and it seems preferable to regard A. arcticus as a minor variant. It should be added that the names applied to A. arcticus Bge. are all based on Phaca lapponica sensu DC., non Wahlenberg, of which a lectotypus has been designated above. Bunge’s interpretation of DeCandolle’s intention is here followed, but it should be remarked that DeCandolle cited Table 51 of Oeder’s Flora Danica as illustrating his species. The figure clearly shows wing-petals surpassed by a broad and prominent keel and seems to be a superlatively accurate portrait of A. alpinus sens. str.

Although A. alpinus seems to be most variable, at least in America, north of about lat. 60° N., there is some evidence also of incipient or possibly reliquial racial differentiation in the Rocky Mountains. In this region the relative proportons of the flower parts remain rather constant, but the whole flower varies considerably in size. With very few exceptions the populations found between the Medicine Bow Range in southern Wyoming and the Sangre de Cristo massif in northern New Mexico are perceptibly smaller-flowered than those occurring northward from the Wind River Mountains. It seems probable that the saddle in the Cordillera corresponding with the Red Desert has been as significant a barrier to A. alpinus as to many other plant species. The following figures (in mm.), prepared from over two hundred dissections, illustrate the prevailing differences.

Rocky Mountains from southern Wyoming to northern New Mexico

Calyx (3.2) 3.4-4.6 (4.8)

tube 2.2-3 X 1.3-2.6

teeth 0.9-1.8 (2)

Banner (6.2) 7.4-10 (10.5)

Wings 7.1—9 (9.8)

Keel (7) 7.4-10 (10.5)

Western Wyoming to Alaska, Labrador, and Eurasia

Calyx (4) 4.4-6.6

tube (2.4) 2.7-4 X 2.3-3.7

teeth 1.4-2.8 (3)

Banner (9.5) 10.4-13.6 (14.8)

Wings (8) 9—12 (13.1)

Keel 9-12.5 (12.7)

The existence of two forms native to the Rocky Mountains is not an altogether new idea. Sheldon distinguished (1894, p. 154, as A. astragalinus genuine A. alpinus, which he recognized in America only from Colorado and Labrador, from a larger-flowered A. giganteus (Pall.) Sheld.3 native to the northern Rocky Mountains and equivalent to subsp. alaskanus Hult. Under var. Brunetianus below, attention is drawn to the similarity in the flower between that variety and the Colorado variant of var. alpinus. It seems possible that the two forms are descended together from A. alpinus as it existed at the front of the ice sheets during the Pleistocene glaciations. It would not be remarkable if this precursor stock had handed down a small flower which remained unaltered, while the progeny differentiated on other lines into an eastern (var. Brunetianus) and a Cordilleran (Colorado) race. The larger-flowered A. alpinus could represent a secondary invasion southward from the northern refugia along the Rocky Mountains which reached a dead end at the Red Desert. The form of A. alpinus isolated on lake shores in Bayfield County, Wisconsin, appears from the flower-size to be an immigrant from the north.

Objects

Specimen - 01282190, B. Maguire 26688, Astragalus robbinsii var. alpiniformis (Rydb.) Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Oregon, Wallowa Co.

Specimen - 01282186, B. Maguire 27037, Astragalus robbinsii var. alpiniformis (Rydb.) Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Oregon, Wallowa Co.

Specimen - 01282187, B. Maguire 27037, Astragalus robbinsii var. alpiniformis (Rydb.) Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Oregon, Wallowa Co.

Specimen - 01282188, B. Maguire 27037, Astragalus robbinsii var. alpiniformis (Rydb.) Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Oregon, Wallowa Co.

Specimen - 01282189, B. Maguire 27037, Astragalus robbinsii var. alpiniformis (Rydb.) Barneby, Fabaceae (152.0), Magnoliophyta; North America, United States of America, Oregon, Wallowa Co.

Distribution

Alaska United States of America North America| Washington United States of America North America| Oregon United States of America North America| Idaho United States of America North America| Montana United States of America North America| Wyoming United States of America North America| Colorado United States of America North America| South Dakota United States of America North America| Nevada United States of America North America| New Mexico United States of America North America| Wisconsin United States of America North America| Yukon Canada North America| British Columbia Canada North America| Northwest Territories Canada North America| Alberta Canada North America| Saskatchewan Canada North America| Manitoba Canada North America| Nunavut Canada North America| Ontario Canada North America| Québec Canada North America| Newfoundland and Labrador Canada North America| Scotland Europe| Russia Asia| Europe|