Tortula sayanensis Fedosov & Ignatova, 2025

Tortula sayanensis Fedosov & Ignatova sp. nova. Fig. 3 View Fig .

Diagnosis: In possessing a combination of bordered, partially bistratose leaf margins, papillose laminal cells, paired and fused at bases peristome teeth, and inclined to drooping capsules, the species resembles T. cernua and T. laureri . It differs from both these species in having leaves attenuate into a slender filiform point, partly filled by costa, bordered and regularly serrate upper leaf margins, and yellow setae and capsules; from T. cernua it also differs in having strongly papillose laminal cells and a weakly curved capsules on flexuose or arcuate setae, while from T. laureri it differs in smaller plant size, small- er laminal cells, weaker leaf border, and straight peristome teeth.

Type: Russia, The Republic of Buryatia, East Sayan Mountains, Tunkinsky Distr. , “Tunkinskaya valley” National Park , vicinity of Mondy settl., Hulugayma Creek upper course, 51.735429N, 101.017443E, ca. 2150 m alt., alpine belt, rocks along dry brook bed, in shaded niche on finesoil. 16.VII.2023, V. E. Fedosov 23-0058. Holotype MW ( MW9131307 !). DNA: trn MV: PV170952 , rps 4: PQ593617, ITS PV759590. GoogleMaps

Etymology: the species name refers to the name of the mountain system Sayany, where its type specimen was collected.

Description: Plants in loose tufts or groups, green or yellowish- to brownish-green. Stems up to 0.5 cm long, densely foliate in upper portion, with central strand. Leaves bent inwards or slightly flexuose to contorted when dry, spreading when wet, 1.3–1.6× 0.5–0.65 mm, ovate, oblong to obovate, acute and attenuate into a slen- der filiform point 0.15–0.3 mm long partly filled with costa; margins plane or narrowly recurved at leaf base, entire in basal and middle leaf portion, serrate distally due to protruding cell angles, bordered by 1–3 rows of linear cells in basal and middle leaf portion, and elongate-rhomboid cells distally, cells of leaf border smooth, thick-walled, greenish or yellowish, in 1–2 layers proximally and 1 layer distally, reaching leaf apices; costa excurrent, with quadrate, papillose cells on ventral surface, elongate, smooth or weakly papillose cells on dorsal surface, mostly with 2 guide cells, dorsal stereid band, dorsal epidermis absent or weakly differentiated, and ventral epidermis differentiated; lamina unistratose, often with few bistratose patches; upper leaf cells 13–30×12– 20 µm, rounded-quadrate or polygonal, with numerous, small, C-shaped or branched papillae, opaque; proximal leaf cells rectangular, 45–100(–140)×13–30 µm. Goniautoicous, perigonia well below perichaetia. Setae 0.4–0.7 cm, flexuose or cygneous, yellow, later brownish, rarely slightly reddish proximally. Capsules inclined, horizontal to pendent, 1–1.5 mm long, ovate to short cylindric, slightly asymmetric to nearly symmetric, straight to slightly curved, bright yellow. Opercula conic-rostrate. Annuli persistent. Peristome teeth up to 200 µm, arranged in pairs, fused at bases, straight, pale orange to reddish, papillose. Spores 27–35 µm.

Ecology and distribution: This species grows on fine soil in niches and crevices of basic rocks, mainly in the goltsy altitudinal zone (all samples from altitudes above 2000 m a.s.l.). It was collected in several places within the studied area and also in the Okinsky Distr. of Buryatia Republic in the course of the short-term field trip to the vicinity of Okinskie Lakes; also we revealed one specimen of T. sayanensis in the OP collection from Tyva Republic .

Differentiation: In combination of widely ovate to obovate, bordered leaves, densely papillose laminal cells, and inclined to pendent capsules, T. sayanensis resembles T. laureri ; these two species are also close phylogenetically. Moreover, both species occur in the same area, although in somewhat different ecotopes: T. laureri was found in sheltered humid niches in forest zone, while T. sayanensis occurs in subalpine and alpine zones, growing in dry niches between rocks. Morphological differences of T. sayanensis include smaller size of plants, with leaves 1.3–1.6 mm long vs 3.5–5 mm in T. laureri ; upper leaf cells 12–15 µm vs 17–40 µm; and setae 0.4– 0.7 cm vs 1–1.5 cm. In T. sayanensis , smooth, thick-walled cells of the leaf border are in 1–3 rows, partly bistratose in one row, weakly inflated, reaching leaf apex; they become elongate-rhomboid distally, and their protruding upper angles form a regular serration. In T. laureri , cells of leaf border are in 3–5 rows in proximal part of leaves, more clearly inflated, bistratose in 1–2 rows, border disappears in the upper leaf portion, not reaching leaf apex; one or few teeth often occur near apiculus, but regular serrulation is absent. In T. sayanensis , upper leaf margins form a right angle at apex, and costae is excurrent as slender filiform point, while in T. laureri upper leaf margins form a wider angle, and leaves have short, attenuate, reflexed apiculi. Setae and young capsules in T. sayanensis are bright yellow vs reddish in T. laureri , and peristome teeth in T. sayanensis are shorter (up to 200 µm), straight vs reaching 350 µm, oblique in T. laureri . Superficially T. sayanensis may resemble T. cernua , which is very variable in size, capsule shape, degree of leaf lamina papillosity, and leaf border expression. However, in the latter species leaves have a sharp mucro, papillae occur mostly in distal leaf portion around the costa, gradually disappearing towards margins or absent; setae are straight, and both setae and capsules are dark brown, red to blackish.

Affinities: T. sayanensis is closely related to T. laureri , which sporadically occurs in South Siberian mountains from East Sayan to Transbaikalia.

Other specimens examined ( paratypes): RUSSIA: Republic of Buryatia: (1) East Sayan Mountains, Tunkinsky Distr., “Tunkinskaya valley” National Park, vicinity of Mondy settl., upper limit of forest belt on southern slope of Hulugaisha Mt., 51.71789N, 101.00191E, ca. 2042 m alt., calcareous rock outcrops along the ridge, in rock niche. 10.VII.2023, Fedosov s.n. (MW). (2) Okinsky Distr., vicinity of Okinskie Lakes in the watershed of Oka and Irkut Rivers, northward the road Mondy- Orlik, 51.94012N, 100.65123E, ca. 2203 m alt., steep rocky slope with rock outcrops, in ledge on finesoil. 13.VII.2023, Fedosov 23-0060 (MW9131306); Isolate TF53, DNA: trn MV PV170951, rps 4 PQ593616, ITS PV759589. Republic of Tyva: Mongun-Taiga Distr., Mongun-Taiga Mt., NE-macroslope, Mugur River basin, 50.30905N, 90.21408E, 2760 m alt., Dryas -dominated tundra, on bare soil. 30.VII.2019, Pisarenko (NSK2010622). Tortula laureri specimens used for DNA study: Russia: Buryatia republic, Mondy settl. vicinity, 10.VII.2023, V.E. Fedosov, MW9131300. Isolate TF54, DNA: trnMV PV170953, rps4 PQ593618, ITS PV759588. The same place and date, MW9131354. Isolate TF59, DNA: trnMV PV170954, rps4 PQ593619. Zabaikalsky Territory, Agin-Buryat Autonomous Area, Alkhanai National Park, rock outcrops near waterfall, 24.VII.2007, O.M. Afonina 8307 (MHA9110782). Isolate BF199, DNA: ITS PV759587.

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