Didymodon perobtusus Broth., Rev. Bryol.

Afonina, M. A., Kuznetsova, O. I. & Ignatova, E. A., 2022, A revision of the Didymodon perobtusus group (Pottiaceae, Bryophyta) in Russia, Arctoa 31 (2), pp. 191-204 : 196-203

Didymodon perobtusus Broth., Rev. Bryol. , n.s. 2: 1. 1928. — Barbula perobtusa (Broth.) P.C. Chen, Hedwigia 80: 194. 28 f. 1–5. 1941. Figs. 3-5 , 2 A-I, 10

Plants in low, dense tufts, dark brown to black, dull. Stems 3–6 mm, sparsely branched, hyalodermis absent, cortical cells in 1–2 rows, medullar cells in 2–3 rows, + thick-walled, central strand narrow or well-developed. Leaves loosely to tightly appressed when dry, erect when moist, the middle part of stems 0.3–0.5× 0.15–0.25 mm, upper and subperichaetial leaves 0.6–1.0× 0.3–0.4 mm, ovate to ovate-lanceolate, gradually tapered to apex or with shoulders, rounded-obtuse at apex, concave, not keeled distally; margins plane or widely recurved in midleaf, crenulate distally; costa thin, ca. 20–25 µm wide at base, not narrowed distally, ending a few cells before apex, semicircular in transverse section, with 2 guide cells, ventral and dorsal epidermis and 0–1 layered dorsal stereid band; laminal cells thick-walled, upper and middle laminal cells round or transversely ovate, 5–15×7–10 µm, papillose, papillae simple, 1–2 per cell, or smooth; basal juxtacostal cells quadrate to short rectangular, 10–20×8– 11 µm, smooth, basal marginal cells in several rows rounded-quadrate, ovate or transversely ovate. Specialized vegetative reproduction by 1(2)-celled gemmae 17– 23 µm in diameter, born in clusters in leaf axils. Dioicous, sporophytes rare. Male plants smaller than female, with several perigonia per stem. Perigonial leaves widely ovate, strongly concave, rounded at apex, with hyaline basal part. Perichaetial leaves 1.2–1.4× 0.3–0.4 mm, oblong-lanceolate, gradually tapered to apex. Setae ca. 4 mm, reddish-brown, flattened and spirally twisted when dry. Urn cylindrical, 0.8 mm long, 0.2 mm wide, gradually narrowed to the mouth, dark cherry-red, smooth. Annulus deciduous. Operculum long rostrate, ca. 0.6 mm long. Peristome teeth slightly twisted when dry, straight when wet, 130–170 mm long, horizontally striolate and finely papillose. Spores 9–11 µm.

Distribution and ecology. In Russia Didymodon perobtusus occurs in the mountainous areas of southern Siberia. It is most frequent in the East Sayan Mts and is known from several localities in NE surroundings of Baikal Lake, Transbaikalia, Tyva Republic, and Altai Mts. It was also collected on limestone massif Yanganape on eastern slope of Polar Urals. It occurs in altitude range 600–2300 m, growing on base-rich rock outcrops on slopes and on river banks, on rocky slopes, on wet cliffs and rocks near waterfalls.

Differentiation. Didymodon perobtusus differs from most species of Didymodon by having dark-brown color of plants, ovate leaves with crenulate upper margins, and mostly unicellular axillary gemmae. Its distinction from the similar D. subandreaeoides is discussed under that species. It can be also confused with Bryoerythrophyllum inaequalifolium (Taylor) R.H. Zander , which has similar leaf shape and unicellular gemmae. The latter species differs in having leaves with more strongly recurved margins, densely papillose laminal cells, with c-shaped papillae, and costae with two well-developed stereid bands.

Specimens examined: MONGOLIA: Kosogol [Khubsugul]

Lake, 27 July 1902 Elenkin (LE) (Syntype). RUSSIA: Yamalo-

Nentzky Autonomous District: Eastern slope of Polar Urals, Yanganape limestone massif, Fedosov 17-1005, MW9113061 . Altai Republic: Ongudai Distr., Maly Yaloman Creek, 31 July 1991 Ignatov & Ignatova 25/170, MHA9108774 ; Teletzkoe Lake , Izvestkovaya Mt. , 12 July 1989 Ignatov s.n., MHA9108775 . Irkutsk Province: Slyudyanka Distr. , Slyudyanka River valley , right bank, Ignatov et al. 18-4503, MHA9027592 ; same place, left bank, Ignatov et al. 18-4620, MHA9027423 . Zabaikalsky Territory : Kalar District , Kodar Range : Valley of Syulban River , left bank of Khadatkan River , 22 June 2015 Afonina 3215, LE B-0039664; Priargynsky District , Byrka Settl., 30 June1989 Bardunov s.n., LE B-0039680. Republic of Buryatia: East Sayan Mts : Okinsky District , East Sayan Mts. : valley of Belyi Irkut River , 12 July 2015 Afonina 1615, LE B-0039682; Upper of Oka River , Dodo-Zhahna village , 10 km NE of Orlik Settlement , 2 July2008 Afonina 00708, LE B-0039691; Upper Oka River , valley of Sorok River , 7 July 2008 Afonina 02208, LE B-0039673; same place, 10 July 2008, Afonina & Tubanova ( Bryophyta Rossica et Civitatum Collimitanearum Exsiccata , Fasc. VIII, №296), LE B-0039694; same place, 7 July 2008 Afonina 02108, LE B-0039688; same place, 10.07.2008 Afonina 03608, LE B-0039680, LE B-0039681; Valley of Oka River , Zambbolok Creek , Sailag waterfall, Afonina s.n., LE B-0039704; Tunkinsky National Park , mouth of Bugovek River (right tributary of Irkut River ), Afonina 1222, LE B-0039699; Tunka Distr. , Mondy , 24 Aug 1960 Bardunov s.n., LE B-0039677; Tunka Range , Khubuta River , 3 Aug 1960 Bardunov s.n., LE B-0039678 .

Didymodon subandreaeoides (Kindb.) R.H. Zander, Phytologia 41: 23. 1978. — Barbula subandreaeoides Kindb., Rev. Bryol. 32: 36. 1905. — Barbula andreaeoides Kindb., Rev. Bryol. 32: 36. 1905. — Grimmia andreaeoides Limpr., Laubm. Deutschl. 1: 776. 1889.

Figs. 6-8 , 2 J-AA, 10. Plants in low, dense tufts, dark brown to black, dull green at shoot tips. Stems 5–8 mm, sparsely branched, hyalodermis absent, cortical cells in 1–2 rows, medullar cells in 1–2 rows, thick-walled, central strand narrow or absent; flagelliform innovations with small, cochleariform leaves always present, scarce to numerous. Leaves on main stems loosely to tightly appressed when dry, erect when moist, 0.35–0.55× 0.25–0.4 mm, ovate to ovate-lanceolate, gradually tapered to apex, rarely with shoulders, rounded-obtuse at apex, concave, not keeled distally; margins plane or widely recurved in midleaf; costa thin, ca. 20 µm wide at base, not narrowed distally, ending few cells before apex, semicircular in transverse section, with 2 guide cells, ventral and dorsal epidermis, 1–2 rows of substereids between guide cells and dorsal epidermis; laminal cells thick-walled, upper and middle laminal cells round or transversely ovate, 7–16×7–12 µm, papillose, papillae low, branched, 1–2 per cell, basal juxtacostal cells 10–20×8–11 µm, smooth, basal marginal cells in several rows round, transversely ovate or ovate. Leaves from flagelliform innovations 0.20–0.25×0.18–0.23 µm, round to widely ovate, strongly concave, costa single, ending below apex or short, occasionally absent; margins entire or, in specimens from Chukotka, with ‘double’ teeth formed by protruding lower angle of upper cell and upper angle of adjacent lower cell. Specialized vegetative reproduction absent or present (in specimens from Yakutia and north of Amur Province), by 1(2)-celled gem-

H I KFig. 7. Didymodon subandreaeoides (from: Russia, Altai Mts , 15 July 1990, Zolotukhin & Korolyeva s.n., MHA9108772 ) . A: leaf transverse section; B: upper leaf cells; C–D, F: stem leaves; E: mid-leaf cells; G, J: leaves from innovations; H: habit, dry; I: basal marginal cells of innovation leaf; K: perichaetial leaf; L: basal leaf cells. Scale bars: 2 mm for H; 0.5 mm for C–D, F–G, JK; 100 µm for A–B, E, I, L.

mae 17–23 µm in diameter, born in clusters in leaf axils. Dioicous, female plants with archegonia occasionally present, male plants not seen. Sporophytes unknown in Russia. [Capsules eperistomate (cf. Inoue et al., 2020)].

Distribution and ecology. Like Didymodon perobtusus , D. subandreaoides occurs in Russia in southern Siberia from Altai to Buryatia and Transbaikalia; it was also found in several localities in Yakutia: Sette Daban, Suntar-Khayata and Ulakhan-Chistai Mt. Ranges, and in Beringian Chukotka. It is also known from single locality in Tokinsky Stanovik Range (Amur Province). The species grows at low altitudes in Chukotka and Yakutia, 50–1000 m a.s.l., while in the mountains of southern Siberia it was found between 1200 and 1700 m. It occurs in arctic and mountain tundra of forb-sedge type, on rock outcrops in moss-lichen community, on boulders in larch forest, on rocky banks of creeks and rivers, on wet limestone cliffs near waterfalls and in places with dripping water (melting permafrost), in Yakutia occasionally in places where Andreaeobryum macrosporum Steere & B.M. Murray was collected.

Differentiation. Didymodon subandreaeoides is very similar to D. perobtusus in plant color, leaf shape, crenulate upper leaf margins, and thick-walled, papillose laminal cells; it even possesses unicellular axillary gemmae in some populations. However, the presence of innovations with small, strongly concave leaves is a unique feature of D. subandreaeoides . It also separates this species from similar species of Didymodon and other genera of the Pottiaceae .

Specimens examined: RUSSIA: Chukotka: Lavrentiy Bay, Krauze Cape , 2 Sept 1975. Afonina s.n., LE B-0039663; Chegitun’ River basin, 24 July1972 Razzhivin s.n., LE B-0039662; same place, 1 km upstream from Putukuneiveem River mouth, 24 July 2003, Razzhivin s.n., LE B-0039661. Republic of Sakha / Yakutia: Momsky Distr., Ulakhan-Chistai Mt. Range , western foothill of Mramornaya Mt. , Ignatov & Ignatova 18- 1360, MW9091288 ; same place, 930 m alt., Ignatov & Ignatova 18-1815, MHA9029531 ; Pravy Dzhapkychan Creek, Ignatov & Ignatova 18-2712, MHA9028794 ; Tomponsky Distr.: left bank of Vostochnaya Khandyga River opposite Segenyakh Creek moutyh, Ivanov 17-729, MHA9027663 ; Sette Daban Range, right slope of Vostochnaya Khandyga River valley between Shaman and Segenyakh Creeks , Ignatov & Ignatova 16-1563, MHA9021499 ; same place, Shaman Creek, Ignatov & Ignatova 17-32, MHA90256925 . Republic of Buryatia: Okinsky

J K

O

District, East Sayan Mts.: upper of Oka River , Valley of Sorok River , alt. 1755 m, 9 July 2008 Afonina 03008, LE B-0039657; Okinsky District , East Sayan Mts , Valley of Belyi Irkut River , 12 July 2015 Afonina 1715, LE B-0039656; Kurumkan District , Dzherginskiy State Reserve. Upper Barguzin River , 1 Aug 2013 Mamontov YuSM-386-1, LE B-0039659 & LE B-0039660; NE Baikal, Tompuda River , 19 Aug 1956 Bardunov s.n., LE B-0039658; East Sayan Mts , Kadyr-Os River near Chuglyma Creek mouth, 13 July 1961, Bardunov s.n., MHA9108778 . Z ABAIKALSKY TERRITORY: Kalar District, Kodar Range: Levyi Syulban River , 10 June 2015 Afonina 0715, LE B-0039665; Syulban River , Zolotoi Klyuch Creek , 12 July 2015 Afonina 0915/1, 0915/2 & 0915/3, LE B-0039666, LE B-0039669, LE B-0039670; same place, 13 June 2015 Afonina 1515, LE B-0039667; Kalar District , Kodar Range: Valley of Syulban River , left bank of Khadatkan River , 22 June 2015 Afonina 3215, LE B-0039668; valley of Syulban River , upper of Oleniy Rog Creek , 16.06.2015 Mamontov 536/2b, LE B-0039671; AMUR PROVINCE: Zeya Distr. , Stanovoy Ridge, Tokinsky-Stanovoy National Park , vicinity of the Tas-Balagan pass, Dudov TSMF005 , MW9092493 .

Figures

Fig. 3. Didymodon perobtusus (from syntype). A: gemmae; B-C, H: leaves; D: upper leaf cells; E: habit, dry; F, J: leaf transverse sections; G: mid-leaf cells; I: axillary hair; K: basal leaf cells. Scale bars: 2 mm for E; 1 mm for B-C, H; 100 µm for D, F– G, I-K.

Fig. 5. Didymodon perobtusus (Russia, Buryatia, Tunka Nature Park, Afonina 1222, LE). A: part of peris- tome; B: middle part of peristome teeth; C: lower part of peristome, showing a low basal membrane.Scale bars: 50 µm for A; 10 µm for B; 20 µm for C.

Fig. 2. Leaves of Didymodon perobtusus (A-I) and D. subandreaeoides (J-AA). A-J, L, N, P, R, T, V: stem leaves; K, M,O, Q, S, U, W, Y: leaves from innovations; H-I, Z-AA: perichaetial leaves. All except ‘A’ from Russia. A: Mongolia, isotype, LE; B, H- I: Buryatia, Tunka Nature Park, Afonina 1222, LE (OK3413); C: Polar Urals, MW9113059 (OK3425); D: Altai, Yaloman, MHA9108774; E: Altai, Teletzkoe Lake, MHA9108775; F: Irkutsk Prov., Slyudyanka, MHA9027582; G: Irkutsk Prov., Slyudyanka, MHA9027410; J-K: Chukotka, MHA9109069; L-M: Altai Mts., Shapshal Range, MHA9108772 (LC545517); N-O: East Sayan Mts., MHA9108778; P-Q, Z: NW Baikal, MHA9108773; R-S, AA: Yakutia, Ulakhan-Chistai Range, MHA9028965 (OK3426); T- U: Yakutia, Suntar-Khayata Range, MHA9021523 (OK3427); V-W: Yakutia, Ulakan-Chistai Range, MW9092629 (OK3434); X- Y: Yakutia, Sette-Daban, MHA9021486 (OK3428). All specimens of D. subandreaeoides from Yakutia possess both flagelliform innovations and axillary gemmae. Scale bars: 0.5 mm for all.

Fig. 6. Didymodon subandreaeoides (from: Russia, Chukotka, 2 Sept 1975, Afonina s.n., MHA9109069). A: mid-leaf cells; B: upper leaf cells; C–D, G, M–N: stem leaves; E–F: leaf transverse sections; H: basal leaf cells; I: habit, dry; J, L: leaves from innovations; K: basal marginal cells of innovation leaf; O: stem transverse section. Scale bars: 2 mm for I; 0.5 mm for C–D, G, M– N; 100 µm for A–B, E–F, H, K, O.

Fig. 8. Didymodon subandreaeoides (from: Russia, Yakutia, Sette Daban Range, Ivanov 17-605, MHA9027661). A: habit, dry; B–C: leaf transverse sections; D: gemmae; E: upper leaf cells; F, K: lower stem leaves; G: leaf from innovation; H: stem transverse section; I: mid-leaf cells; J: perichaetial leaf; L: subperiachaetial leaf; M: basal leaf cells. Scale bars: 2 mm for A; 0.5 mm for F– G, J–L; 100 µm for B–E, H–I, M.