Atraphaxis, Linnaeus, 1753

Yurtseva, Olga V., Vasilieva, Natalia V., Kostikova, Vera A. & Samigullin, Tahir H., 2022, A broadly sampled 3 - loci plastid phylogeny of Atraphaxis (Polygoneae, Polygonoideae, Polygonaceae) reveals new taxa: III. A. kuvaevii and сryptic species in A. pungens from Southern Siberia and Northern Mongolia, Phytotaxa 566 (1), pp. 13-63 : 44-45

Key to the species of Atraphaxis growing in Mongolia, Altai, Southern Siberia and Russian Transbaikalia

1. Perianth with two inner and two outer tepals, 6 stamens, lenticular fruit with two styles................................................................ 2

— Perianth with three inner and two outer tepals, 8 stamens, trigonous fruit with 3 styles ................................................................. 4

2. Leaf blades shortly puberulent abaxially. Altai Mts, Zaisan ........................................................................................ A. canescens

— Leaf blades glabrous ......................................................................................................................................................................... 3

3. Inner perianth tepals reniform, 7–9 × 9–11 mm, 1.5–2 times longer than fruits. Altai Mts, Zaisan .............................. A. compacta

— Inner perianth tepals rotundate, 5–6 × 7–8 mm, almost equal to fruits ........................................................................... A. replicata

4. Outer perianth tepals 1.5 times shorter than inner tepals, outspread in fruiting. All perianth tepals depart from a cup-shaped extention of a filiform perianth tube 0.7–1.0 mm long joint to a pedicel 2.0–3.0 mm long ...................................... A. selengensis

— Outer perianth tepals 2–3 times shorter than inner tepals, reflected to a pedicel in fruiting. All the tepals depart from the top of a wedge-shaped extention of a filiform perianth tube 2.5–6.0 mm long, equal to a pedicel .............................................................. 5

5. Subshrub or shrub with orthotropic generative shoots terminated with thyrse 5–25 cm long, sometimes branching, never prickly after fruiting ...................................................................................................................................................................................... 6

— Shrub with sturdy and prickly second-year shoots and axillary branchlets bearing lateral generative shoots with compact thyrses 1.5–4 cm long ................................................................................................................................................................................... 8

6. Shrub up to 100 cm tall. Generative shoot terminates with branched thyrse 10–25 cm long with well spaced cymes of flowers. Leaf blades broadly elliptical ..................................................................................................................................................... A. virgata

— Subshrub 20–70 mm tall. Generative shoot terminates with thyrse 5–12 cm long with 8–12 congested cymes of flowers, sometimes with paracladia. Leaf blades oblanceolate or linear-lanceolate ........................................................................................................ 7

7. Leaf blades oblanceolate, with net of veins, more than 3 mm in width. Ochreolas transparent...... A. frutescens subsp. frutescens

— Leaf blades linear-lanceolate, with a midvein beneath, less than 3 mm in width, ochreolas herbaceous ........................................... ............................................................................................................................................................... A. frutescens subsp. sibirica

8. Annual shoots and edges of leaf blades shortly papillose. Fruits light-brown ................................................................................. 9

— Annual shoots and leaf blades glabrous. Fruits black or dark-brown ............................................................................................ 10

9. Leaf blades bright-green, rotundate to broadly elliptical, 7–15 × 8–10 mm. Tepals white or creamy, inner tepals 5–6 × 6–7 mm. Perianth tube is twice longer than a pedicel. Achene 2–3 times shorter than inner tepals. Kazakhstan, Altai Mts, Saur, Tarbagatay, Dzungaria ..................................................................................................................................................................... A. laetevirens

— Leaf blades dark-green, rhomboid-ovate to rhomboid-elliptical, 8–11 × 2–6 mm. Tepals dark-green with pink margin, inner tepals 3–4 × 2–4 mm. Perianth tube articulated to a pedicel in ochreola.Achene is equal or slightly shorter than inner tepals. Krasnoyarskii Krai, Tuva ......................................................................................................................................................................... A. kuvaevii

10. Ochreas 7–9(12) mm long. Fruits black, lanceolate, finely pitted or microtuberculate (× 4), glossy, equal to inner tepals of perianth. Styles fused to 1/3–2/5, 0.6–0.8 mm long, stygmas spongy, campaniform in flowering. Transbaikalia ........................ A. davurica

— Ochreas 3–7 mm long. Fruits black or dark-brown, ovoid to lanceolate, smooth, glossy, twice shorter or equal to inner tepals of perianth. Styles fused to 1/4–1/5, 0.3–0.5 mm long, stygmas globular or flat, in flowering bent to ovary. Altai Mts, Khakassia, Krasnoyarskii Krai, Tuva, Mongolia.............................................................................................................................................. 11

11. Leaf blades broadly elliptical to oblanceolate, gradually narrowed to a petiole, leaf ratio 3–7. Inner tepals of perianth 4–6 × 4–6 mm. Fruits black and glossy, ovoid, 2.4–3.3 × 1.4–2.0 mm, twice shorter than inner tepals 4–6 × 4.5–6 mm. Krasnoyarskii Krai, Khakassia, Tuva, Mongolia.............................................................................................................................................. A. pungens Note: Hybrids of A. × uyukensis (the Uyuk ridge) have black ovoid fruits with microtuberculate surface, 4.1 × 2.0 mm. Hybrids A. pungens × A. frutescens subsp. sibirica have dark-brown lanceolate fruits 2.8 × 1.3 mm with distinct ribs.

— Leaf blades rhomboid-elliptical, broadly elliptical, or obovate, leaf ratio 2–3. Fruits dark-brown to black, 2.8–4.5 × 1.4–2.0 mm, 1.5 times shorter than inner tepals of perianth, which are 5–7 × 5–7 mm. Mongolia, Altai Mts, Tuva ....................... A. ledebourii Note: Hybrids Atraphaxis ledebourii × A. frutescens subsp. sibirica have dark-brown lanceolate fruits 4.5 × 2.0 mm with distinct ribs.