Calliergon giganteum subsp. sibiricum Ignatova

Calliergon giganteum subsp. sibiricum Ignatova &

Czernyadjeva, subsp. nov. Figs. 6 View Fig , 5 View Fig : E–L, 7.

Holotype: Right bank of Tirekhtyakh River in middle course, west of Mramornaya Mt., 64°52’43"N, 146°31’13"E, 1240 m alt., flat depression with lakes, flooded site with Carex stans between lakes, 14 July 2018, Ignatov & Ignatova 18-1525 (Holotype: MHA 9028275!, isotype MW 9091937!). Figs. 6 View Fig , 7.

Diagnosis: Dioicous Calliergon , differs from C. gigantum in weak costa and from C. megalophyllum in large alar groups.

Description: Plants medium-sized, green or olivaceous-green. Stems 3–7(–15) cm long, simple, irregularly branched or, rarer, pinnately branched. Stem leaves appressed to erect, (1.2–)1.7–2.7(–3.3)×(0.9–)1.2–1.4 (–2.2) mm; ovate or ovate-triangular, rounded at apex, cordate at base, concave; costa thin, reaches 0.9–1.0 leaf length, rarely in largest leaves only 0.7 the leaf length, often indistinct in upper portion, (50–)60–80(–180) µm wide at base, (20–)25–40(–60) µm wide at one third the leaf length; median laminal cells (40)50–65(–120)×(4.5–) 6–7.5(–10) µm, with moderately thickened walls; alar cells large, thin-walled, forming large, sharply delimit- ed group reaching (0.5–)0.7–0.9(–1.0) the distance from leaf margin to costa. Dioicous, sporophytes rare. Male plants not seen. Inner perichaetial leaves 2.25–2.5× 0.9– 1.2 mm, straight, not plicate, oblong-triangular, strongly concave, subobtuse at apex, with entire margins, costa single, thin, reaching 0.65–0.95 of leaf length. Setae 3– 4 cm long, reddish-brown. Capsules inclined to horizontal, oblong, curved, occasionally with mouth turned down-

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wards, ca. 2 mm long, brownish. Operculum conic, with short obtuse beak. Peristome perfect; exostome teeth 600– 700 µm long, light brownish, on dorsal surface finely striolate-reticulate below, finely papillose above; endostome with high basal membrane, segments about the same length as exostome teeth, perforated, finely papillose, cilia 2–3, long, nodose to shortly appendiculate. Spores 13– 18 µm, finely papillose. Calyptrae not seen.

Distribution and ecology. The subspecies occurs in the tundra zone and in mires in permafrost regions of the boreal zone, occasionally in the upper belts of high mountains in continental areas. Fig. 4C–D View Fig shows approximate limits of the species distribution; preliminary attempts to find it in Europe failed. Because the easternmost localities of dioicous Calliergon belong to C. gi-

Рис. 7. Calliergon giganteum subsp. sibiricum (from holotype): A: leaf; B: alar and basal laminal cells; C: upper laminal cells and end of costa, note its indistinct outlines in uppermost part.

ganteum s.str., we presume that C. giganteum subsp. sibiricum is absent in oceanic regions of the Russian Far East. Collections were done in a variety of wet grasslands, boggy forests, and mires.

Differentiation and variation. Besides the combination of a thin costa and large alar groups, Calliergon giganteum subsp. sibiricum can be preliminary identified by a small plant size ( Fig. 6 View Fig ). Leaf length and width are, however, often correlated with plants that are robust or slender and show only small difference from C. giganteum subsp. giganteum . However, in northern Siberia where the latter subspecies was so far not found, the problem of differentiation of plants in the field is separation from C. megalophyllum , and for that this character works well.

Another trait that often is conspicuous in C. giganteum subsp. sibiricum is a costa that is gradually vanished in its uppermost part and it is somewhat difficult to decide exactly where it ends (Fig. 7C). In some especially large leaves the costa ends far below the leaf apex: one such leaf is shown in Fig. 5L View Fig . Such plants could be identified as C. richardsonii , so DNA was re-extracted and re-sequenced to confirm the identity of this specimen with most other specimens of C. giganteum subsp. sibiricum .

Specimens examined: (other than those in Appendix 1, with sequenced samples).

Selected specimens examined: RUSSIA: Altai Territory: Biisky Okrug, Malyi Ad mire, 27 Jul 1928, Sheludyakova s.n. (LE). Amur Province, Bysa River, 25 Aug 1927, Kuzeneva 88 (LE); Zeya River basin, Bomnak River, 28 Aug 1910, Abramov 121 (LE). Arkhangelsk Province: Franz Josef Land, Meibl Island, 28 Jul 1979, Safronova s.n. (LE); Franz Josef Land, Hooker Island, 80°20’18.7’’N, 52°47’27.6’’E, 29 Jul 2019, Konoreva 913 (LE). Buryatia Republic, West Sayan, Oka River, 52°34’N, 100°07’E, 9 Jul 2008, Afonina 02808 (LE); Mukhorshibirsky District, Bolshoy Sibilduy River, 50°48’57’’N, 107°20’18’’E, 25 Aug 2018, Afonina s.n. (LE, #1218). Chukotsky Autonomous District: Ioni Lake, 3 Jul 1977, Afonina s.n. (LE); Yanrakynnot Settlement, 20 Jul 1976, Afonina s.n. (LE); Amguema River, 17 Aug 1970, Afonina s.n. (LE); Aion Island, 19 Jul 1983, Afonina CH-00064 (LE); Il’myneiveem River, 30 Jul 1978, Afonina s.n. (LE); Vrangel Island, Somnitelnaya Bay, 23 Jul 1985, Afonina s.n. (LE). Krasnoyarsk Territory: Kureika station, 17 Sept 1933, Sokolov s.n. (LE, #26); Archipelago Severnaya Zemlya , Island of the October Revolution, 24 Aug 1975, Safronova s.n. (LE); Evenkia, Turukhansk Region, Lower Tunguska River, 9 Jul 1932, Rubin & Maskil s.n. (LE); Chunya River, 9 Jul 1931, Rubin s.n. (LE); Taimyr Autonomous District: mouth of Malaya Logata River, 98°24’N, 73°25’E, 5 Aug 1988, Pospelova s.n. (MW9026350); Lake Syrutaturku, 73°35’N, 97°30’E, Pospelova 94/55 & 94/66 (MW9026351, MW9026352); West Taimyr, Willem Barentz Biostation, Meduza Bay, 20 Jul 2001, Varlygina s.n. (MW9026276); Afanas’evskie Lakes, 71.5896°N, 106.117°E, Fedosov 06-64 (MW9026280); between Afanas’evskie Lakes and Fomich River, 71.6208°N, 106.315°E, Fedosov 06-442 (MW9026274); mouth of Kogotok Creek, 70.8195°N, 100.983°E, Fedosov 09-227 (MW9026273); Nyurai-tar Creek – left tributary of Bikada River, 17 Aug 1978, Sokolova s.n. (MW9026284); northern edge of Anabar Plateau, watershed of Popigai and Anabarka Rivers, 72.1283°N, 110.702°E, Fedosov 08-305 (MW9010425); Taimyr, Dixon Island, 7 Aug 1954, Dorogostaiskaya (LE); Uboinaya River, 19 Aug. 1988, Kannukene s.n. (LE, #14975); Mamontova River, 12 Aug. 1949, Tikhomirov & Uvarov s.n. (LE); Kresty Settlement, Aug. 1976, Matveeva s.n. (LE); Tareya Settlement, 22 Jul 1970, Blagodatskikh s.n. (LE); Novaya River, Ary-Mas, 1 Aug. 1972, Afonina s.n. (LE); Plateau Putorana, Ayan Lake, 23 Jul 1983, Czernyadjeva 88 (LE); Plateau Putorana, Lama Lake, Jul 1984, Czernyadjeva 65 (LE). Kamchatsky Territory: Paratunka Riv- er, 25 June 1957, anonym (LE). Khabarovsk Territory, Nikolaevsky District, Kulchi Settlement, 13 Aug 1964, Ganeka s.n. (LE). Magadan Province: Chaunsky District, 18 Jul 1977, Blagodatskikh s.n. (LE); Olsky District, Atargan Settlement, 29 Jul 1978, Blagodatskikh s.n. (LE). Zabaikalsky Territory: vicinity of Nerchinsk Town, 4 Jul 1908, Novopokrovskij 1564 (LE); Sokhondinski Reserve, 49°27’N, 110°51’E, 11 Jul 2010, Czernyadjeva 8-10 (LE); Gazimuro-Zavodskiy District, 52°14’48’’N, 119°23’22’’E, 22 Jul 2012, Afonina 2912 (LE); Kalarsky District, Naminga Settlement, 56°36’N, 118°32’E, 2 Aug 1985, Filin s.n. (LE, MW); Alkhanay National Park, 50°48’N, 113°03’E, 16 Jul 2005, Afonina 1005 (LE). Tuva Republic: East Tannu-Ola Range, 50.90890°N, 94.32896°E, 30 Jun 2018, Pisarenko tv18-5d (LE). Yamalo-Nenetzky Autonomous District: Yamal, Junto Lake, 67°40’N, 68°00’E, 10 Aug 1993, Czernyadjeva 56 (LE); Yamal, vicinity Syunyaj-Sale Settlement, 66°55’N, 71°20’E, 26 Jul 1996, Czernyadjeva 42 (LE). Republic of Sakha /Yakutia: Momsky District: Ulakhan-Chistai Mt. Range, west of Mramornaya Mt., 64°52’43”N, 146°31’13”E, Ignatov & Ignatova 18-1523 (MHA9028171); middle course of Tirekhtyakh River, Ulakhan-Chistai Mt. Range, 64°54’28”N, 146°25’52”E, Ignatov & Ignatova 18-1897 (MHA9092425); lower course of Tirekhtyakh River, Tymny- Ulakh Creek, 64°10’33”N, 146°45’09”E; Ignatov & Ignatova 18-2498 (MHA9029134); Khangalassky District: Ulakhan Keteme Creek near road to Tit-Ary, 61°15’50”N, 128°05’09”E, Ignatov & Ignatova 16-165 (MHA9022144); Tomponsky District: between Khandyga and Teplyi Klyuch Settlements, 62°45’28”N, 136°28’19”E, Ignatov & Ignatova 18-1214 (MHA9027704); New Siberian Islands, Stolbovoi Island, 74°10’31.2’’N, 135°27’36.6’’E, 3 Aug 2019, Czernyadjeva 8- 19 (LE); New Siberian Islands, Kotelny Island, 25 May 1947, Gorodkov s.n. (LE); New Siberian Islands, Bolshoi Lyakhovsky Island, 73°20’N, 140°00’E, 25 Aug 1956, Pigulevskaya s.n. (LE); Tiksi, 71°40’42.6’’N, 128°51’7.1’’E, 30 Jul 2019, Czernyadjeva 3-19 (LE); delta of Lena River, Samoilovsky Island, 72°22’N, 126°29’E, Aug 1998, Zhurbenko s.n. (LE); lower course of Indigirka River, 17 Aug 1974, Afonina s.n. (LE); Medvezhji Islands Archipelago, Chetyrekhstolbovoi Island, 70°37’N, 162°27’E, 7 Aug 1980, Zaslavskaja s.n. (LE); Nizhnekolymsk District, Pokhodsk Village, 6 Aug. 1973, Stepanova 2/6 (LE); Suntarsky District, Vilui River basin, 5 Aug. 1958, Kildyushevsky 77/5 (LE); Indigirka River basin, Moma River, 66.5°N, 30 May 1936, Sheludyakova s.n. (LE); Lensk District, Dzerba River basin, 60°29’N, 116°50’E, 20 Jul 2000, Ivanova s.n. (LE); Tomponsky District, Delinnya River, 28 Jun 1955, V. Ivanova s.n. (LE); Olekminsk District, Tokko River, 20 Jul 1995, Krivoshapkin 02.04.01.09 (LE).

Comment on the subspecies’ distribution. The distribution of dioicous taxa of Calliergon giganteum group ( Figs. 4C–D View Fig ; 8 View Fig ) shows that subsp. sibiricum appears to be restricted mostly to areas with permafrost, and it is absent in the extensive boggy lowland of West Siberia and oceanic regions along Pacific coast of Asia where Calliergon giganteum subsp. giganteum occurs ( Figs. 4C– D View Fig ; 8 View Fig ). Interestingly, in the severe climate of the Transbaikalia, with local (though not rare) permafrost spots, Calliergon giganteum subsp. sibiricum appears to be much more common than subsp. giganteum .

Comment on phytogeography. In general, the known distribution of Calliergon giganteum subsp. sibiricum is similar to some common Yakutian species, e.g. Tomentypnum involutum (Limpr.) Hedenäs & Ignatov ( Hedenäs et al., 2020) . However, in contrast to T. involutum , which populations in Yakutia are sympatric with T. nitens , a widespread Holarctic species, the distributions of C. giganteum subsp. sibiricum and subsp. giganteum hardly overlap.

A more similar situation has been found by Hedenäs (2009) for Scorpidium cossonii – S. scorpioides complex. Scorpidium scorpioides has obviously evolved inside basal S. cossonii ; similarly, Calliergon megalophyllum originated from C. giganteum s.l., that gave also a lineage of C. giganteum s.str. In both cases ‘ancestral’ grades (of S. cossonii and C. giganteum subsp. sibiricum ) have Arctic to northern distributions. In both cases the derivatives, S. scorpioides and C. megalophyllum received a rather strong morphological difference and bigger size, and also both latter species often grow submerged, at least for larg- er parts of their bodies.

Hedenäs (2009) estimated that S. cossonii must have evolved before the general cooling of the climate started in Pliocene, earlier than the Arctic region expanded. As the complex of the dioicous Calliergon taxa received a stronger genetic differentiation, we may suggest that it is likely no less ancient; moreover, C. giganteum was re-

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ported from Late Miocene or Pliocene deposits of Beaufort Formation ( Kuc & Hills, 1971; Kuc, 1973). Although the overlap in distribution of C. giganteum subsp. giganteum and subsp. sibiricum is considerably smaller compared to that for haplopypes of Scorpidium cossonii ( Hedenäs, 2009) , the genetic isolation between these C. giganteum subspecies seems to be not strict.