Panarctic Flora

320209 Luzula arcuata (Wahlenb.) Sw.

• Sw., Summa Veg. Scand.: 13 (1814). - Juncus arcuatus Wahlenb., Fl. Lapp.: 87 (1812) nom. cons.. Lectotype (UPS): Sweden: "Piteå lappmark på Örfjället", 06. Sept. 1807, leg. Wahlenberg typ. cons. (Moberg and Nilsson 1991: 293).

Geography: Amphi-Atlantic & amphi-Pacific/Beringian.

Notes: Egorova (PAF proposal), supported by Yurtsev, accepted three species: the mainly North Atlantic Luzula arcuata s. str. but with scattered records from the Beringian regions, the amphi-Beringian L. beringensis, and the amphi-Pacific L. kamtschadalorum. Kirschner et al. (2002a, in comments) accepted L. arcuata with two subspecies: a strictly Atlantiic subsp. arcuata and a Pacific/Beringian subsp. unalaschkensis. The latter taxon - according to Kirschner - clearly covers the types of both "kamtschadalorum" and "beringensis". Egorova and Yurtsev disputed this conclusion, see comments under subsp. unalaschkensis. We follow Kirschner's treatment with some comments and one major modification.

Egorova et al.: Hultén (1968a, 1968b) accepted two subspecies of L. arcuata in Alaska and Chukotka: subsp. arcuata (including L. beringensis) and subsp. unalaschkensis (including L. kamtschadalorum). We all agree that the names "unalaschkensis" and "kamtschadalorum" are synonymous; the former has priority for a subspecies (Hultén 1968b), the latter for a species (Krylov 1929).

Egorova and Yurtsev argued for two morphologically and eco-geographically different Beringian and Pacific taxa. In their opinion, the taxon to which they assigned the name "beringensis" is northernly distributed and occurs along the Koryak coast, in East Chukotka, and in Alaska. It grows in dry, stony or gravelly sites with comparatively little snow cover and predominantly on acidic bedrock. Yurtsev stated that "beringensis" and "kamtschadalorum" are ecological vicariants (dry exposed ridges and slopes vs. snowbeds) in their large area of overlap of ranges.

According to Yurtsev, "beringensis" differs from North Atlantic "arcuata" in, e.g., purplish basal sheaths (more red than in L. confusa), narrower, channelled leaves etc. Elven stated that also the European L. arcuata s. str. has beautifully purplish basal sheaths and narrow channeled leaves. These are two of the characters used for its recognition, and it is therefore not readily separable from "beringensis" by these characters. Already Hultén (1968b: 32) pointed out Tolmachev's error in characters of the northwestern European plants (which is the one repeated by Yurtsev). Egorova added the following characters: L. beringensis differs from L. arcuata s. str. in a characteristic structure of the inflorescence with numerous vs. 2-4 (5) capitulas as well as normal presence in the inflorescence of a long lateral branch remote from the terminal part. Such a lateral branch is, according to her, never present in L. arcuata s. str. Elven stated that well developed Scandinavian plants of L. arcuata s. str. may have many (often 10 or more) and often loose and few-flowered capitulas and one or more long lateral branches, see, e.g., the illustrations in Mossberg and Stenberg (2003) and in Elven et al. (2005), drawn on, respectively, southern and northern Norwegian plants. Egorova's comment indicates that she has compared with plants that would be considered as L. confusa in the current Nordic opinion. Elven and Murray, from field experiences with both plants and comparing material (ALA and O), were not able to divide Beringian material assigned under the name "beringensis" from Fennoscandian material of "arcuata" s. str. on two subspecies on morphological evidence. The name "beringensis" may be misapplied but there is a Beringian plant much more similar to Atlantic L. arcuata s. str. than to Pacific "unalaschkensis"-"kamtschadalorum".

The "unalaschkensis"-"kamtschadalorum" taxon has no Atlantic parallel morphologically. It is more southernly distributed than the Beringian plant commented on above, reaching south to Kamtchatka in the Russian Far East and far south in the Cordillera in Canada. It is typical of snowbeds, long snow-covered boulder scree, and wet morainic gravel by glaciers, and also seems to prefer acidic substrates. Egorova reported the following characters of L. beringensis (her concept) vs. L. kamtschadalorum: Both taxa have a similar inflorescence but in L. beringensis, in contrast to L. kamtschadalorum, leaves are narrow, usually canaliculate, with deep purple sheaths (in radical leaves), whereas in L. kamtschadalorum the leaves are broad and flat and the sheaths pale brown or yellowish. As for the plants on the American side, Elven concurs that there are such differences (morphological and ecological) between, e.g., a restricted western Alaskan plant and a widespread one in Alaska and the Yukon Territory.

Much of the problems are due to the probably erroneous application of the name "beringensis" by Russian authors for the narrowly Beringian plant above. Hämet-Ahti (1973) referred L. beringensis to the synonymy of L. arcuata subsp. unalaschkensis. This was the solution for North America by Swab (2000) and is Kirschner's conclusion after examination of the types of "beringensis", "kamtschadalorum", and "unalaschkensis". Note that the types of all the three names are from fairly southern and oceanic parts (respectivelly, Koryak, Kamtchatka, and Unalaska) and may well belong to the same taxon (as Kirschner concludes), whereas the other proposed taxon that we discuss is more northern (western Alaska and the Chukchi Peninsula). A rapid survey by Murray and Elven in 2009 (material in ALA) showed the plant with narrow, canaliculate leaves and purplish sheaths to be restricted to the westernmost parts of Alaska, whereas broad-leaved plants with brown or yellowish sheaths occurred both within its range and south, east, and northeast of it, e.g., as far north as northern Alaska and the northern Yukon Territory.

Elven & Murray: After our survey of material, we accept two taxa in the Beringian regions but as subsp. unalaschkensis (incl. L. beringensis and L. kamtschadalorum) and subsp. arcuata. Subspecies arcuata is then widely disjunct with one Atlantic part area and another Beringian one. Presence of subsp. arcuata in western Alaska and the Chukchi Peninsula is supported by specimens (ALA, O).