Atraphaxis kamelinii O.V.Yurtseva, 2016

Yurtseva, Olga V., Kuznetsova, Oxana I. & Mavrodiev, Evgeny V., 2016, A broadly sampled 3 - loci plastid phylogeny of Atraphaxis (Polygoneae, Polygonoideae, Polygonaceae) reveals new taxa: I. Atraphaxis kamelinii spec. nov. from Mongolia, Phytotaxa 268 (1), pp. 1-24 : 11-16

Atraphaxis kamelinii O.V.Yurtseva , spec. nov. ( Figs. 2–5 )

Type:— MONGOLIA. [Khovd aimag]: the Dzungarian Gobi, S slope of Saertaengijin-Khuvch Uul [Mt.] near junction to Khaldzan-Ula [Mts.], 27 July 1984, Daryima & Kamelin 765 ( LE! holotype).

Shrubs ca 1 m tall. Stem erect, stout, glabrous; woody shoots inclined-spreading, brown, much branched, not spiny, slightly ribbed, creamy, epidermis exfoliating and fibrously disintegrating, making light-brown or creamy wood. Current-year shoots are branched forming racemes of thyrses with branchlets departing at a nearly right angle. Annual shoots and branchlets 10–15 cm long are straight, soon lignified, slightly ribbed, glabrous, leafy with internodes 5–10 mm, or terminated by thyrses 5–10 cm long with 5–10 spaced cymes of 1–3 flowers in axils of developed or reduced leaf blades. Ocreas at vegetative shoots are tubulate, 5–6 mm, membranous, brownish at base, transparent above and cleft into two linear-lanceolate lacinulas with two faintly visible veins at both sides of leaf blade, and finely incisoserrated short middle lacinula. Ocreolas in thyrses are oblique funnel-form, 2–5 mm, membranous, brownish at base, transparent above and cleft into 2 sharp teeth. Leaf blades bluish-green or glaucous, thick, oblong-elliptic, 10–20 × 5–10 mm, gradually narrowed to a petiole 1.5–3 mm, glabrous, with prominent midvein and faint lateral veins. Margin entire, flat, or slightly revolute, glabrous, apex obtuse or short-pointed. Segments 4 or rarely 5, bright-pink; outer segments two, reflexed towards pedicel in fruit, reniform-orbicular, ca. 2.0–2.8 × 3.0 mm, prominently reticulateveined; inner segments two or three, circular-reniform in fruit, 4.5–5.9 × 6.0– 7.5 mm in diam., base nearly cordate, venation prominently reticulate, margin slightly undulate. Perianth tube 2.0– 2.5 mm, filiform, joined to a pedicel (ca. 4.5 mm long) with articulation. Stamens 8, filaments subulate-lanceolate, gradually dilatated towards base. Achenes 4.2–4.5 × 2.5 mm, ovoid, gradually acuminate, lenticular or unequally-trigonous, with strongly concave faces, ribs sharp, almost winged, surface smooth, glossy, dark-brown to black.

Styles 2(3), 0.3 mm long, fused at the base, with stigmas capitate, papillate.

Fl.— May–June. Fr.— June–Aug.

Distribution:— Endemic of the Dzungarian Gobi in SW Mongolia, Khovd aimag ( Fig. 6 ).

Ecology:— Mountain slopes, granites, sandy sairs.

Etymology:—The species is named after Rudolf V. Kamelin (1938–2016), famous for his studies on the flora and florogenesis of Central Asia.

Taxonomic relationships:— The new species might be closely related to A. pungens as a putative maternal taxon, with which it shares the shrubby habit, branchlets of the annual shoots departing at almost right angle, elliptical or rhomboid-elliptical leaf blades, black glossy achenes, perianth size, but differs by creamy-pinkish, not spiny second-year shoots, and mainly dimerous flowers.

Atraphaxis kamelinii also resembles A. virgata because of the shrubby habit and racemes of thyrses, but differs in the shape and venation of leaf blades, far-spaced cymes of flowers, circular-reniform inner segments, and black, glossy, and mainly lenticular achenes.

The new species is similar to A. bracteata due to the shrubby habit and racemes of thyrses, but differs by creamy annual shoots, elliptical bluish-green leaf blades entire at the margin, outer perianth segments reflected to a pedicel and mainly lenticular achenes.

It is morphologically similar to A. spinosa and A. compacta with mainly tetramerous flowers, almost reniform inner segments and lenticular achenes, but differs by lacking spiny shoots, elongated thyrses with 5–10 spaced cymes of flowers, and achenes that are almost black and glossy.

Other specimen seen (paratype):— MONGOLIA. Khovd (=Khobdo) aimag: the Dzungarian Gobi, [somon Bulgan], 15 km S of the settlement Bulgan, granites, sandy sairs, N 45°57’, E 91°31’, 17 June 2004, Dyachenko & Kosachev (ALTB!).

Figures

FIGURE 2. Holotype of Atraphaxis kamelinii O.V.Yurtseva, sp. nov. Image: O. Yurtseva.

FIGURE 3. Shoots and thyrses of Atraphaxis kamelinii (LE! holotype, see also Fig. 2). A. Bracteose thyrses with spaced cymes of 1–2 dimerous flowers; B. Top of annual shoot with branchlets terminated by thyrses; C, D. Abaxial and adaxial view of leaf blades; E. The bases of annual shoots with axillary vegetative and generative branchlets. Scale bar = 1 mm (C–D). Images: O. Yurtseva.

FIGURE 4. Perianths and achenes of Atraphaxis kamelinii (LE! holotype). A. Cyme of two flowers with tetramerous (on the left) and pentamerous (on the right) perianths; B, C. Flower with pentamerous perianth and trimerous gynoecium; D. Flower with tetramerous perianth (inner segment is removed) hiding lenticular achene; E. The top of triquetrous achene with three styles and capitate stigmas; F. Triquetrous achenes; G. Three style branches fused at the base and terminated by capitate stigmas. Scale bar = 1 mm (A–F); = 0.5 mm (G). Images: O. Yurtseva.

FIGURE 5. Perianths (A–I) and achenes (J–L) of Atraphaxis kamelinii, A. compacta, A. replicata, A. virgata, and A. pungens. A–B. A. kamelinii from the Dzungarian Gobi, Daryima & Kamelin 765 (LE); C. A. compacta, Kazakhstan, Pavlov 160 (MW); D. A. replicata, Kuvaev 518-3 (MW); E. A. virgata, Mongolia, Gubanov 2634 (MW); F, J–K. A. pungens, Russia, Tuva, Neifeld & Margasova (MHA); G. A. pungens, Mongolia, Gubanov 3563 (MW); H, L. A. pungens, Mongolia, Volkova & Rachkovskaya 7373 (LE); I. A. pungens, Russia, Tuva, Maltseva & Selisheva (MW). Scale bar = 1 mm (A–I); = 0.2 mm (K); = 0.5mm (J, L). Images: O. Yurtseva.

FIGURE 6. Distribution map of Atraphaxis kamelinii. Distribution area is indicated by black circle. Map: M. Olonova.