Plagiothecium curvifolium Schlieph. ex Limpr., Laubm. Deutschl.

Ignatova, E. A., Fedorova, A. V., Kuznetsova, O. I. & Ignatov, M. S., 2019, Taxonomy of the Plagiothecium laetum complex (Plagiotheciaceae, Bryophyta) in Russia, Arctoa 28 (1), pp. 28-45 : 36-38

Plagiothecium curvifolium Schlieph. ex Limpr., Laubm. Deutschl. 3: 269. 1897. — Plagiothecium denticulatum var. curvifolium (Schlieph. ex Limpr.) Meylan, Bull. Soc. Vaud. Sci. Nat. ser. 5, 41: 151. 1905. Fig. 7 .

Description. Plants medium-sized, in more or less dense, somewhat rigid lustrous mats. Stems creeping, 1– 3 cm long, foliage complanate to more commonly subcomplanate due to homomallous leaves. Leaves forming 30–50° angle with stem, curved towards substrate by their distal part, 1.3–2.0(–2.2) × 0.55–0.9 mm; ovate-oblong, more or less symmetric to slightly asymmetric, concave (in slides plicate and crumpled), tapered to acute apex or shortly acuminate, decurrent in 2–4 rows of rectangular to almost quadrate cells; leaf margins narrowly recurved on one or both sides, occasionally flat, entire or faintly denticulate at apex; costa short and double; laminal cells 80–150 × 6–10 µm. Gemmae rarely present, of 3–4 quadrate or short rectangular cells. Autoicous. Sporophytes usually present. Setae 15–20 mm long; capsules curved, inclined to horizontal, 1.5–2.0 mm long. Exostome teeth ca. 500 µm long; basal membrane of endostome ca. 200 µm high, segments slightly longer than exostome teeth, cilia 2, 300 µm long, distinctly nodose. Spores 9–12 µm.

Distribution and ecology. The species is rather common in European Russia, although more rare compared to P. denticulatum and P. rossicum . It occurs in boreal and hemiboreal forests of European Russia, partly in broadleaved forests, and in the Caucasus. No specimens were seen from the Asian Russia, except for eastern slope of subpolar Ural Mts. The species grows on trunk bases, fresh logs, stumps, sometimes of sandy soil on vertical banks along roads, occasionally on rocks. The habitat where this species is more common than other species of the genus are exserted roots of Pinus sylvestris in mesic to moderately dry forest types.

Differentiation. Specimens of P. curvifolium are usually easy to identify due to their characteristic foliage: leaves of this species are curved towards substrate, not flattened and therefore are usually variously plicate and folded in slides under cover glass ( Fig. 7 ). This feature is combined with partially recurved leaf margins and leaf cells variable in width (6–10 µm). Capsules of P. curvifolium are the longest within the P. laetum complex and are usually markedly curved and inclined; the exostome teeth are also longer than in other species of the group, ca. 500 µm long. However, some sequenced specimens with less markedly curved leaves were resolved within the P. curvifolium clade. They could most likely be confused with P. laetum , which is most similar in leaf shape (moderately asymmetrical, with acute or very shortly attenuate apical portion, and partially recurved margins). In such cases, leaf cell width may be helpful (6–10 µm in P. curvifolium vs. 6–8 µm in P. laetum ). If sporophytes are present, distinctly curved capsules up to 2 mm long are characteristic for P. curvifolium rather than for P. laetum , which often has shorter capsules, straight and erect or slightly curved and inclined. As for the other two species of the P. laetum complex, P. rossicum is distinguished from P. curvifolium by flat leaf margins and narrower, 6–7 µm wide, leaf cells, while P. svalbardense differs from it by its smaller size, usually stronger branched stems, and a distinctly attenuate leaf apex.

Selected specimens examined: EUROPEAN RUSSIA: Murmansk Province: Tersky Distr. , Porja Guba, Kozhin M-M-1785 ( MW9077455 ) ; Arkhangelsk Province: Pinega Nature Reserve , 8.VIII.1988, Ignatov s.n. ( MHA9041583 ) ; Bolshoi Solovetsky Island , 20.VII.1998, Churakova 235 ( MW9055387 ) ; Komi Republic: Sosnogorsk Distr., Nizhny Odes , 26. VI.2007, Kucherov & Kutenkov 14 ( MHA 9041603 ) ; Pechoro-Ilychsky Nature Reserve, Smirnova 87 ( MW9055022 ) ; Perm Province: Dobryansky Distr., Verkh-Kvazhva Setl. , 3.VIII.2005, Bezgodov & Shkaraba 36 ( MW9055024 ) ; Moscow Province: Zvenigor- od biostation of Moscow State University , 19. VI.2018, Ignatov s.n. ( MW9110620 ) ; Vladimir Province: Aleksandrov, Seregin M-382 ( MW9055015 ) ; Torfoprodukt , 10.IX.2008, Kokoshnikova s.n. ( MW9055016 ) . CAUCASUS: Republic of Karachaevo-Cherkessia: Teberda Nature Reserve, Severny Klukhor Gorge , 8.IX.1994, Onipchenko 174/94 ( MW9055444 ). ASIAN RUSSIA: Khanty-Mansiisk Autonomous District : Berezov

16 17 18

distr., subpolar Urals , Neroika Mt., 64°33’08.3”N, 50°42’50.4”E, 9.VIII.2013, Lapshina 13-589 ( MHA9023468 ) .

UKRAINE: Volyn Province, Seltsy Gornitskie, 18.VII.1949, Bradis s.n. ( MW9055303 ) . GERMANY: Hessen, XI.1900 Roth s.n. ( E. Nauer, MEE 670; MW9055009 ) . POLAND: Silesia Inferior, Walbrzych, 23.VIII.1979 Berdowski 1274 ( MW9055012 ) ; Warmian-Masurian Voivodeship, Olsztyn, S eregin & Kolodziej M-3131 ( MW9055011 ) .

Figures

Fig. 7. Plagiothecium curvifolium (from: 1–3: Germany, Mosses of Saarlandes 2573, 6.IV.1991, Caspari s.n., SAAR; 4–6: Germany, Mosses of Saarlandes 7591, 28.XII,2011, Caspari s.n., SAAR; 7–9: Germany, Mosses of Saarlandes 7495, 26.X.2006, Caspari s.n., SAAR; 10–12: Russia, Kaliningrad Province, 3.IV.2005, Rozhina s.n., MHA9041610; 13–15: Russia, Caucasus, Karachaevo-Cherkessia, Onipchenko 174/94, MW9055444; 16–18: Russia, Komi Republic, Kucherov & Kutenkov 175, MHA9023477): 1–2, 4–5, 7–8, 10–11, 13–14, 16–17 – leaves; 3, 6. 9, 12, 15, 18 – midleaf cells. Scale bars: 1 mm for 1–2, 4–5, 7– 8, 10–11, 13–14, 16–17; 100 µm for 3, 6. 9, 12, 15, 18.