53.20 Arabidopsis (DC.) Heynh. in Holl & Heynh. (1842), Fl. Sachs. 1: 538.
[BY]
B
S
Arabis auct., non L. (1753); Halimolobus auct., non Tausch (1836), Flora 19: 410.
Comments:
(1)
A small species of ca 10 species, predominantly Asian, represented in the Arctic by
3-4 taxa of sect. Toxophylla N. Busch. They are biennials to subperennials
(oligocarpics) of an A. bursifolia aggregate with glabrous siliques and with
disjunctive area of distribution centered in Beringia. Almost all the taxa of this
aggregate were originally described in the genus Arabis L. in the tribe Arabideae and
later transferred to Arabidopsis in the tribe Sisymbreae (seeds dorsal-rooted, sticky
when wet; siliques terete, etc.): Arabis trichopoda Turcz. to Arabidopsis trichopoda
(Turcz.) Botsch. to Arabidopsis bursifolia; Arabis tschuktschorum Jurtz. to
Arabidopsis tschuktschorum (Jurtz.) Jurtz.; and Arabis hookeri Lange to Arabidopsis
mollis (Hook.) O.E. Schulz.
After Rollins' monograph of western N American Arabis (Rollins 1941,
Rhodora 43), North American authors refer Arabis hookeri to the North American
Cordilleran oligotypic genus Halimolobus Tausch, comprising robust perennials
(some of them subshrubs), densely pubescent with soft branched hairs (incl. siliques)
and with very thin and long styles. Typical representatives of the genus Halimolobus
are H. patula Tausch and H. stricta Tausch (isotypes in LE!) whereas the Cordilleran
H. virgatus (Nutt.) O.E. Schulz is closely related to H. mollis (acc. to Rollins loc. cit.
and A.E. Porsild) and may belong to the genus Arabidopsis as well. (Yurtsev)
(2)
Yurtsev's account of Arabidopsis have only been slightly edited linguistically. You
should look into his arguments carefully. They are very relevant for how we - in
general - should handle cases of deviating marginal populations. (Elven)
53.20.1 Arabidopsis bursifolia (DC.) Botsch. (1959), Bot. Mater. Gerb. Bot. Inst. AN SSSR
19: 106.
B
Nasturtium bursifolium DC. (1821), Syst. Nat. 2: 194.
S
Comments:
(1)
Arabidopsis bursifolia and A. mollis are both strongly variable plants but the ranges
of their variability are practically identical. Comparison of anatomical structure of
some parts of siliques, kindly performed by E. Velitschkin, in plants from the lower
reaches of Kolyma R. (A. bursifolia) and W Greenland (A. mollis) revealed some
distinctions, e.g., shape of cells in the mechanical tissue of the inner walls of valves
(almost round in A. mollis, multiangular in A. bursifolia). However, one should check
whether these distinctions are stable. At the present stage of knowledge it is more safe
to unite both entities under the priority name Arabidopsis bursifolia until a more
monographic treatment has been performed.
Arabidopsis bursifolia s. lat. (incl. A. mollis) is a continental, essentially
subarctic plant of ruderal strategy (see Yurtsev in Tolm. 1975, Fl. Arct. URSS 7: 5359). Its favourite habitats in the Arctic are tors and other dining places of birds of
prey. As a consequence, the local populations are usually very poor in individuals. A
large gap separates the marginal populations of A. bursifolia in Asian and American
Arctic, between the lower reaches of the Amguema R. in the isthmus of Chukchi
Peninsula and the lower reaches of Mackenzie R. (or the upper reaches of Koyukuk
R. in subarctic Alaska). This gap was most probably brought about by the Holocene
humidification of climate following upon the shelf flooding in Central Beringia.
Approximately at the center of this gap two dwarfish, strongly isolated populations
have been discovered, deviating much even from a rather variable A. bursifolia. The
distinction of one of them corresponds to the rank of variety whereas that of the other
corresponds to the rank of species. The situation could be explained in terms of gene
drift in very small populations under marginal climatic conditions.
Despite of different environments, the plants of both varieties have many
features in common such as: mono- to oligocarpic life cycle; erect stems with
sagittate oblanceolate acutish leaves with long auricles; caducous sepals covered by
simple hairs with an admixture of branched ones; siliques widest in the middle part
with thich mid-vein; and septum with very thin median vein, without perforations.
(Yurtsev)
53.20.1.1 Arabidopsis bursifolia (DC.) Botsch. var. bursifolia
S
?Arabidopsis mollis (Hook.) O.E. Schulz (1933), Bot. Jahrb. 66: 97 [basionym:
Turritis mollis Hook. (1829), Fl. Bor.-Amer. 1: 40.]; ?Halimolobus mollis (Hook.)
Rollins (1941), Rhodora 43: 480; ?Arabis hookeri Lange (1880), Consp. Fl. Groenl.
3: 50; Arabidopsis trichopoda (Turcz.) Botsch. (1957), Bot. Mater. Gerb. Bot. Inst.
AN SSSR 18: 104 [basionym: Arabis trichopoda Turcz. (1840), Bull. Soc.
Naturalistes Moscou 8, 1: 63].
2n=
(1) 16 (2x). (2) 20.
2nD
(1) Jørgensen et al. (1958 Grl, A. mollis); Mulligan (1964 Can, A. mollis); Berkutenko
& Gursenkov (1976 NE As Magadan area, A. bursifolia); Zhukova et al. (1977 N Sib,
A. bursifolia). (2) Rollins (1993, secondary reference).
G
SIB RFE ALA CAN GRL
Comments:
(1)
Confined to dry, continental areas and sites with sparse vegetation and low
competition. A high inter-population polymorphism is notable in this race, more or
less similar throughout the range. (Yurtsev)
53.20.1.2 Arabidopsis bursifolia (DC.) Botsch. var. beringensis Jurtz. in Tolm. (1975), Fl.
Arct. URSS 7: 58.
S
T
Russian Far East: Peninsulae Tschukotskij pars boreali-orientalis, prope ostiam fl.
Chegitun, 08.08.1972, leg. B. Jurtzev, N. Sekretareva & A. Sytin (LE) holotype.
2n=
2nD
G
RFE
Comments:
(1)
Differs from the type variety, besides the smaller size of many parts and their
numbers, also by siliques more abruptly (not gradually) angustate towards both base
and apex, and seeds ellipsoid (not oblong).
A very small population on the top of a calcareous tor, together with
Erysimum pallasii and Androsace septentrionalis, at the edge of a grassy meadow, 34 km from the seashore. (Yurtsev)
53.20.2 Arabidopsis tschuktschorum (Jurtz.) Jurtz. (1975), Bot. Zhurn. 60: 240.
B
Arabis tschuktschorum Jurtz. (1974), Bot. Zhurn. 59: 1462.
S
T
Russian Far East: Penunsulae Tschukotskij pars boreali-orientalis, ad fl. Putukuneiveem. 22.07.1972, leg. B. Jurtzev (LE) holotype.
2n=
16 (2x).
2nD
Zhukova in Yurtsev (1974 E Chuk).
G
RFE
Comments:
(1)
A very small population on the flat top of a calcareous low mount, in ornithogenic
dry meadow surrounded by tufts of Carex hepburnii and Smelowskia porsildii s. lat.,
40 km south of the locality of A. bursifolia var. beringensis. 2n=16 was counted a few
days later in the same population.
Besides a number of distinctive features in the habit (e.g., ascendent-prostrate
floriferous stems with wider obtusate leaves with or without very short auricles,
infloresence of numerous congested flowers, polycarpic lofe cycle, thicker rugose
taproot), the plant differs from Arabidopsis bursifolia s. lat. in sepals persistent (not
caducous), densely pubescent with minute ramose hairs, siliques widest above the
middle part, septum with one wide perforation and one distinct marginal median vein.
Gene drift in a very small and isolated marginal population might be responsible for
these significant differences which have not been recorded in others of the numerous
small isolated populations of A. bursifolia. (Yurtsev)
53.21 Alyssum L. (1753), Sp. Pl. 650. [RE]
53.21.1 Alyssum obovatum (C.A. Mey.) Turcz. (1837), Bull. Soc. Imp. Naturalistes Moscou
10: 57.
B
Odontarrhena obovata C.A. Mey. in Ledeb. (1831), Fl. Altaic. 3: 61.
S
A. americanum E.L. Greene (1892), Pittonia 2: 224.
2n=
(1) 16 (2x). (2) 30. (3) 32 (4x).
2nD
(1-3) Rollins (1993). (1) Krasnoborov et al. (1980 Sib); Numeri Chromos. Fl. URSS
(1990 Sib). (3) Numeri Chromos. Fl. URSS (1990 Chukotka).
G
RUS SIB RFE ALA CAN
Comments:
(1)
Reaches the Arctic in Polar Ural. Arctic occurrences further east, in Siberia, are more
dubious acc. to the map by Hultén (1968) but the species is mapped more or less
throughout arctic Siberia and Far East by Tolmachev (1975). In Alaska it is not
mapped from the arctic parts by Hultén (1968) but is mapped from Brooks Range by
Porsild & Cody (1980) and from arctic Yukon Territory by Cody (1996). (Elven)
53.22 Lesquerella S. Wats. (1888), Proc Amer. Acad. Arts 23: 249. [RE]
53.22.1 Lesquerella arctica (Wormsk. ex Hornem.) S. Wats. (1888), Proc. Amer. Acad. Arts
23: 254.
B
Alyssum arcticum Wormsk. ex Hornem. (1818), Fl. Dan. 9, 26: 3, t. 1520.
S
2n=
60 (12x).
2nD
Löve & Löve (1975) list six counts, four as arctic.
G
SIB RFE ALA CAN GRL
Comments:
53.22.2 Lesquerella calderi G. Mulligan & A.E. Porsild (1969), Canad. J. Bot.
S
L. arctica (Wormsk. ex Hornem.) S. Wats. subsp. calderi (G. Mulligan & A.E.
Porsild) Hultén (1973), Bot. Not. 126: 488.
2n=
20 (4x).
2nD
Mulligan & Porsild (1969a).
G
CAN
Comments:
(1)
The ploidy difference, also confirmed by Rollins (1993), supports the status as a
species separate from L. arctica. (Elven)