Pseudotaxiphyllum undetermined

Afonina, O. M., Kazanovsky, S. G., Pisarenko, O. Yu., Fedorova, A. V. & Ignatova, E. A., 2019, Pseudotaxiphyllum subfalcatum (Plagiotheciaceae Bryophyta) in Asia: one more species with An Arcto-Tertiary disjunction, Arctoa 28 (2), pp. 143-148 : 146-148

KEY TO THE IDENTIFICATION OF PSEUDOTAXIPHYLLUM SPECIES IN RUSSIA

1. Leaves +symmetrical, from ovate base abruptly or gradually narrowed into filiform acumen; axillary brood branches with leaflets along their bodies ...... ................................................................. P. elegans

— Leaves asymmetrical, cultriform, acute at apex; axillary brood branches with leaflets restricted to their apices ..................................................................... 2

2. Axillary brood branches born in leaf axils throughout the stem, more than 3 cells wide ....................... ........................................................ P. distichaceum

— Axillary brood branches born in leaf axils only at shoot apex, 2–3 cells wide ............... P. subfalcatum

Pseudotaxiphyllum subfalcatum (Austin) X.Q. Li, Q. Zuo & Y.F. Wang, J. Syst. Evol. 53(2): 188. 2015. — Plagiothecium subfalcatum Austin, Musci Appalach. 366[schedae 61]. 1870. — Isopterygium subfalcatum (Austin) A. Jaeger, Ber. Thätigk. St. Gallischen Naturwiss. Ges. 1876 –77: 438 (Gen. Sp. Musc. 2: 504). 1878. – Pseudotaxiphyllum distichaceum auct. non (Mitt.) Z. Iwats. ( Fig. 2 and 3 : 9–12, 15).

Plants small to medium-sized, light green, glossy, forming flat mats. Stems simple or irregularly branched, complanate-foliate. Leaves 1.1–2.0 mm long and ca. 0.5 mm wide, spreading, often undulate, oblong to oblonglanceolate, asymmetrical, cultriforme, acute; margins plane or narrowly recurved at base, serrate at apex, below serrulate to mid-leaf; costa short and double; mid-leaf cells linear-flexuose, 50–75(–88)×7–8 µm, at apex shorter, rhomboidal; alar cells not differentiated. Specialized asexual reproduction by axillary propagules (brood branches) usually present in leaf axils at shoot tips; brood branches numerous, 0.2–0.6 mm long, twisted-vermiform, 2–3 cells wide, with 1–5 acute, erect leaflets at apex. Gametangia not seen in specimen from Russia. [Dioicous. Sporophytes unknown.]

Specimens examined: RUSSIA: Republic of Buryatia, Kabansky Distr., Baikalsky Nature Reserve, right bank of Vydrinaya River , 51°25’38,1”N, 104°54’21,0”E, 565 m alt., SWfaced slope ca. 20° with rock outcrops, mixed forest of birch, Siberian pine, spruce and fir with Bergenia crassifolia , 9.VIII.2011, Kazanovsky s.n. ( LE, MHA) . The plant was presumably collected on ledge of rock outcrop. Sakhalinskaya Province, South Kuril Islands, Iturup Island , Medvezh’ya Bay , 45.416°N, 148.826°E, 150 m alt., creek in the lower part of Nfaced slope of Medvezh’ya Mt. , 15.IX.2015 Pisarenko op05831 ( MW 9060912 , duplicate from NSK) .

Distribution and ecology. Until now, P. subfalcatum was known in eastern North America, as well as Central and South America; in N. America it occurs from Arkansas and Georgia to Ontario and Quebec, typically growing on moist cliffs of acid rocks, on ledges, and in crevices, sometimes on peaty soil in woods ( Crum & Anderson, 1981; Ireland, 2014). In Asiatic Russia it was also collect- ed in shaded and rather moist environments, especially in Iturup Island, where this species grows on volcanic rocks along small stream covered with soil and moist debris. This creek runs on slope of old volcano covered by secondary vegetation formed after fire by Sasa sp. thickets and sparse trees of Larix kamtschatica ; these thickets are so dense, that form a pipe-like corridor 2-4 m wide along the stream bed and making this space wet and shady.

Differentiation. Specimens of P. subfalcatum from Buryatia are similar to the widespread SE Asia P. distichaceum , in their asymmetrical, cultriform leaves with acute apices and twisted-vermicular axillary brood branches with apical leaflets. However, these plants of P. subfalcatum lack red pigmentation, which is often present in plants of P. distichaceum (e.g. in Russian collections from the Kuril Islands); in P. subfalcatum brood branches are born in the leaf axils only at the shoot apices, while in P. distichaceum the brood branches are present in the leaf axils along the whole stem; and the brood branches of P. subfalcatum are smaller and narrower, 2–3 cells wide, whereas in P. distichaceum they are longer and wider, 4–5 cells wide ( Fig. 3 ).

Figures

Fig. 2. Pseudotaxiphyllum subfalcatum (from: Russia, Buryatia, 9.VIII.2011 Kazanovsky s.n., LE, MHA). 1 – habit, dry; 2 shoot apex with axillary propagules; 3 – upper laminal cells; 4 – median laminal cells; 5–7 – leaves; 8–10 – axillary propagula; 11 – basal laminal cells. Scale bars: 2 mm for 1; 1 mm for 5–7; 0.5 mm for 2; 200 µm for 8–10; 100 µm for 3–4, 11.

Fig. 3. 1–4, 13: Pseudotaxiphyllum elegans (from: Russia, Chukotka, Lavrentia settlement, 10.VIII.1969 Afonina s.n., LE); 5–8, 14: P. distichaceum (from: Russia, Kunashir Island, Ignatov 06-1697, MHA); 9–12, 15: P. subfalcatum (from: Russia, Buryatia, 9.VIII.2011 Kazanovsky s.n., LE, MHA). 1–2, 5–6, 9–10 – axillary propagula; 3–4, 7–8, 11–12 – leaves; 13–15 – habit, dry. Scale bars: 2 mm for 13–15; 1 mm for 3–4, 7–8, 11–12; 200 µm for 1–2, 5–6, 9–10.