Taraxacum humifusum Štěpánek & Kirschner, 2022

Štěpánek, Jan & Kirschner, Jan, 2022, A hotspot of endemism: Oreophytic Taraxacum species (Compositae, Crepidinae) in the mountains of Bulgaria, Phytotaxa 569 (1), pp. 1-139 : 58-59

4. Taraxacum humifusum Štěpánek & Kirschner , sp. nov.

Type:— Bulgaria, montes Pirin , opp. Bansko , vallis flum. Banderica , locis graminosis herbosisque subalpinis secundum viam turisticam rubre signatam in declivitate ± orientali in vallis rivi Vichrenska voda supra casam alpinam Vichren (1950 m), inter montes Chvojnati vrch (2635 m) et Vichren (2914 m), ca. 2200–2400 m, 41° 45–46’ N, 23° 24–25’ E, 9 Aug 1997, J. Štěpánek, J. Kirschner & B. Trávníček, cultivated as JŠ 6550, collected in 1999 ( PRA, no. det. 35728, holotype; isotype: PRA, no. det. 26126, and duplicates) .

Etymology:—Low, prostrate, appressed to the ground (a compound word, derived from Latin humus, ground, and fusus, spread out).

Diagnosis:—Rosula foliorum terrae adpressa, pallide viridis, glaberrima, foliis subrigidis, immaculatis, involucrum olivaceo-viridescens, phyllariis exterioribus numerosis, variabiliter laxe adpressis, erectis, erecto-patentibus vel subpatentibus, obscure olivaceo-viridibus, immarginatis, acheniis olivaceo-brunneis, brunneo-griseis vel obscure griseis, superne dense squamulosis spinulis interspersis, corpore in pyramidem subcylindricam vel subconicam, crassiusculam, 0.4–0.7 mm longam subabrupte transeunte.

Plants small, 4–7 cm tall. Plant base without tunic, glabrous, leaf rosette light green, compact. Petiole very broadly winged (narrowly so in the innermost leaves), pale, to pale green, usually 1.5–2 cm long. Leaves prostrate, appressed to the ground, stiff, light green, not spotted, ± glabrous, oblanceolate to elliptical in outline, usually 3–7 × 1.5–3 cm, pinnatipartite to pinnatisect; terminal segment relatively small, most often 0.7–1.5 × (1.0–) 1.3–2.2 cm, flat rhombic in outline, usually trilobed, terminal lobule acute, lingulate, distal margin usually concave, sometimes sigmoid, usually entire, basal lobules patent, narrowly triangular, oblong to lingulate, acute, proximal margin subconvex, entire, often raised; lateral segments in 3–4 pairs, usually patent, narrowly triangular to deltoid-triangular, often with an elongated, patent to forward-pointing distal part, distal margin convex or concave, entire or with one to several minute acute teeth or with a distinct incision, often undulate; proximal margin convex to ± straight, often raised, entire or with a single narrow teeth near the base; interlobes usually 2–8 × 3–5 mm, green, not bordered, entire, sometimes with a single large tooth or lobule, always raised; mid-vein pale greenish. Scapes pale greenish, very sparsely arachnoid, shorter than leaf length. Capitulum deep yellow, 2.5–3.5 cm wide, ± flat. Involucre olivaceous-green, very slightly pruinose, 7–8 mm wide and ± rounded at base. Outer phyllaries 18–23, variously loosely appressed, erect or erect-patent to patent, often the innermost ones appressed, the outermost ones patent, lanceolate to narrowly lanceolate, usually 4.5–6.5 × 1.5–2 mm, reaching 1/3–1/2 of the inner, ± evenly dark olivaceous-green (darkening when dry), border not developed, margin and apex often suffused black-purple, not ciliate, apex flat; inner phyllaries 11–12 mm long, of equal width. Outer ligules ± flat, striped purplish dark grey outside, apical teeth dark greyish to dirty yellow, inner ligules ± canaliculate, their apical teeth deep yellow. Stigmas medium discoloured, greyish to yellowish light green, most of the stigmatic hairs hyaline, some with grey or grey-black apex. Pollen present, pollen grains irregular in size. Achenes olivaceous grey-brown, brownish grey to grey, 3.6–4.2 × 0.9–1.0 mm, body with ± dense squamules and interspersed spinules, particularly dense on the top of achene body, forming a low collar masking the cone base, body subabruptly narrowing into a subcylindrical to subconical cone 0.4–0.5 (–0.7) mm long, ca. 0.4 mm thick at base, 0.3 mm distally; beak (4.5–) 7–9.5 mm long, pappus whitish, 4.5–5.5 mm long. – Agamosperm. – Fig. 27C, 29, 30.

Distribution and habitat:—The relatively rich material of T. humifusum is confined to the Vichren Massif, and it is considered to be endemic to the Pirin. It grows in short-grass wet subalpine and alpine grasslands. The IUCN consernation status is estimated as NT.

Diagnostic notes and relationships:—Within T. sect. Bulgarica, T. humifusum is distinct in the combination of light green, unspotted leaves with patent, narrowly triangular, acute lateral segments, outer phyllaries narrow, unbordered, and the peculiar brown-grey achenes. It is most similar to T. bulgaricum (with very different achenes, however) and to T. abnorme (with longer achenes, bordered outer phyllaries and narrower petioles).

The leaf shape and unbordered outer phyllaries make T. humifusum similar to an Alpine species of T. sect. Alpina, T. venustum Dahlstedt (1907: 5) ; syn: T. carinthiacum van Soest (1959: 83) , see Uhlemann (2011). The most striking is the similarity in the leaf shape. However, while T. humifusum does not exhibit much plasticity, T. venustum has a variety of leaf shapes, from a “humifusum-like” leaf to a more complicated pattern with numerous segments and lobules (the T. carinthiacum morphotype). The following Table 4 shows the most important differences between these two species:

Specimens examined:— BULGARIA. Pirin, Bansko , glacial cirque of Goljam Kazan on N. slopes of Mt. Vichren , 2400–2600 m, 15 Aug 1990, J. Štěpánek, cultivated as JŠ 4863 ( PRA, no. det. 26128). – Bansko, Mt. Vichren , ca. 2100 m, 13 Aug 1990, J. Štěpánek, cultivated as JŠ 4854 ( PRA, no. det. 26127). – Bansko , valley of Banderica , below the pass of Vichrenski preslap between Mt. Chvojnati vrch and Mt. Vichren , ca. 2500 m, 12 Aug 1990, J. Štěpánek, cultivated as JŠ 4532 ( PRA, no. det. 26125). – Bansko , lower part glacial cirque of Goljam Kazan on N. slopes of Mt. Vichren , ca. 2400 m, 15 Aug 1990, J. Štěpánek, cultivated as JŠ 4525 ( PRA, no. det. 26124). – Bansko , Banderica valley , between Vichrenski preslap [pass] and the southern foot of Mt. Vichren (2914 m), ca. 2550–2600 m, 41° 45–46’ N, ca. 23° 24’ E, 9 Aug 1997, J. Štěpánek, J. Kirschner & B. Trávníček, cultivated as JŠ 6299 ( PRA, no. det. 26123) ; Ibidem, JŠ 9310 ( PRA, no. det. 26131) ; Ibidem, JŠ 9311 ( PRA, no. det. 26129). – Bansko , in the valley of Vichrenska voda [brook], above the Vichren Chalet , ca. 2300 m, 12 Aug 1990, J. Štěpánek, cultivated as JŠ 4537 ( PRA, no. det. 26130). – Vichren area, slopes above Muratovo ezero, streem banks and path verges, 41° 45’ N, 23° 24’ E, B. Trávníček, cultivated as JK 4338 ( PRA, no. det. 35820). – Banderica , slopes of Mt. Vichren, 9 Aug 1997, J. Kirschner, cultivated as JK 4667 ( PRA, no. det. 35818) .