Taraxacum seminudum Kirschner & Štěpánek, 2025

Kirschner, Jan, Štěpánek, Jan & Buryy, Vladimir V., 2025, Towards a revision of Taraxacum sect. Borealia (Compositae, Crepidinae) in Siberia and the continental Far East, with special reference to the dandelions of the Altai and Kamchatka, Phytotaxa 679 (1), pp. 1-147 : 56-61

20. Taraxacum seminudum Kirschner & Štěpánek , sp. nov.

Type:—[ RUSSIA] Sibiria merid., urbs Bratsk, ad ripam sinistram lacus structilis “Bratskoe More”, ca. 10 km situ a vallo, ad marg. partis centralis urbis Bratsk, haud procul a deversorio “Bratsk”, 27–28 Oct 1985, J . Kirschner & J . Štěpánek , cultivated as JŠ 2597 ( PRA, no. det. 35973, holotype; isotypi: PRA) .

Etymology:—Almost glabrous, half-naked.

Diagnosis:—Plantae foliis glabrescentibus, lobis interlobiisque integerrimis, phyllariis involucralibus exterioribus numerosis, anguste lanceolatis vel lanceolatis apice saepissime corniculatis, cornutis in capitulis posterioribus, marginibus fere invisibilibus, glabris, stigmatibus obscure coloratis, acheniis pallide griseo-stramineis, corpore superne subdense spinuloso spinulis crassiusculis, saepe sursum subcurvatis, pyramide brevi bene dignoscendae.

Plants small, usually 5–10 cm tall. Petiole narrow, unwinged, usually purple, subglabrous to very sparsely arachnoid; plant base with whitish hairs, tunic developed. Leaves mid green to ± bright green, glabrous or with sparsely scattered arachnoid hairs, oblong-linear in outline, usually 5–6 (–8) × (0.9–) 1.1–1.8 (–2.2) cm, regularly pinnatisect, lateral segments narrowly triangular to narrowly triangular-deltoid, usually subrecurved, sometimes to ± patent, distal margin ± straigh, sometimes subconcave or subconvex, entire, proximal margin subconvex or straight, entire; interlobes distinct, 1.5–2.5 mm wide, entire or with 1 (–2) little triangular teeth; terminal segment triangular to tripartite, distal margin concave, entire, basal lobules ± patent, proximal margin ± straight, entire; mid-vein purplish. Scapes brownish green, sometimes suffused purplish, arachnoid, ± overtopping leaves. Capitulum yellow to lighter yellow, 3–4 cm wide. Involucre olivaceous-green, 9–11 mm wide and broadly rounded at base. Outer phyllaries (15) 16–17 (20), appressed, ± not imbricate, narrowly laceolate to lanceolate (seldom linear-lanceolate or ovate), often acuminate, usually (5.0–) 5.5–6 (–7.3) × (1.4–) 2.0–2.5 (–2.8) mm wide (rarely an outermost bract-like phyllary only 1 mm wide), surface olivaceous-green or light so, with distal part dark olivaceous, border almost invisible, membranous to greenish membranous 0.1 (–0.3) mm wide, with a gradual transition into the middle part, margin glabrous, apex callose to dark corniculate, often suffused blackish purple; in later capitula, apex with thick horns. Outer ligules flat, striped greyish or pinkish grey outside, inner ligule teeth dirty yellow or pinkish grey. Stigmas darker discoloured, greenish with grey pubescence outside. Pollen present, pollen grains irregular in size. Achenes light greyish, 3.6–4.4 × 0.9–1.0 mm, body conspicuously, usually subdensely spinulose in upper 1/3, spinules ± thick, usually curved upwards, with apical part ± suberect, body subgradually to subabruptly narrowing into subcylindrical to subconical cone 0.5–0.7 × 0.25–0.3 mm; beak 8–9 mm long, pappus yellowish white, 5–6 mm long. – Agamospermous. – Fig. 4D , 36 , 37 .

Diagnostic notes:—The combination of numerous, appressed to subappressed, relatively narrow, ± lanceolate, almost borderless outer phyllaries, distinctly horned in late capitula, achenes with sparse, short spinulosity, and an almost complete absence of teeth on leaf segment and interlobe margins is diagnostic. It may be considered as intermediate between T. sect. Borealia and T. sect. Dissecta ( Kirschner & Štěpánek 2023b), and the thick horns on later capitula was a character decisive in favour of the former.

Distribution and habitat:— Taraxacum seminudum is known from two rich gatherings and cultivations from the shore of the Bratsk Reservoir in Central Siberia. It grows on gravelly and sandy sites and adjacent grasslands, around 400 m a.s.l.

Specimens examined:—[ RUSSIA] S. Siberia, town of Bratsk, west shore of the “Bratskoe More” reservoir, about 10 km from the dam, not far from the “Bratsk” hotel, 27–28 Oct 1985 , J. Kirschner & J. Štěpánek, cultivated as JŠ 2597 ( PRA, no. det. 35973 and duplicates, isotypes, e.g. PRA, no. det. 37749). – Ibidem, cultivated as JŠ 2596 ( PRA, no. det. 36741). – Ibidem, cultivated as JŠ 2587 ( PRA, no. det. 36743). – Ibidem, cultivated as JŠ 2595 ( PRA, no. det. 36745) .

Species in some aspects close to T. sect. Arctica, usually with dark, not very numerous, almost borderless outer phyllaries

This group, although heterogeneous, includes a number of taxa frequently referred to in the literature. Special attention was paid to T. lateritium and T. macilentum . It should be emphasized that several species have an amphi-Beringian distribution.

In the material from Kamchatka, plants approaching the general habit of T. lateritium are relatively frequent. In a few cases, they represent T. lateritium s. str., i.e., polliniferous plants with reddish achenes. The other specimens are often incomplete (achenes or flowers lacking). They are very close to a similar group of taxa described from Alaska, viz. T. angulatum Haglund (1948: 298) , T. arietinum Haglund (1948: 300) , T. festivum Haglund (1948: 304) , T. speirodon Haglund (1948: 324) , T. maurolepium Haglund (1949: 111) and T. microceras Haglund (1948: 313) . We also have to consider T. alaskanum Rydberg (1901: 512) , frequently reported to belong to T. sect. Arctica but unclear due to its rather inadequate type material. Among the Kamchatka gatherings, there are specimens from three sites near the Ichinskaya Volcano, distinct in their appressed, ovate to ovate lanceolate, narrowly bordered dark outer phyllaries, undivided or obtusely lobulate leaves, absence of pollen, dark stigmas, relatively narrow petioles, and achenes with a very short conical cone. Within the above group, only T. maurolepium corresponds to this character combination, generally rare on the Far East side of the Bering Strait. A comparison of the Kamchatka plants with the type specimens of T. maurolepium confirmed their identity.

It should be emphasized that the concept and an outline of the taxonomic treatment of T. lateritium and T. macilentum fully relies on the taxonomic conclusions drafted by Petr G. Efimov. A more detailed treatment of both taxa and their allies, together with specimen citations and further remarks will be published by him in a separate paper, and we are grateful for his generosity in placing his results at our disposal.

Figures

FIGURE 4. Details of involucres of Taraxacum species from the Altai, in alphabetic order. A, T. peracre (PRA, T 55); B, T. perdecorum (PRA, no. det. 35992); C, T. peschkovae (PRA, no. det. 35855); D, T. seminudum (PRA, JŠ 2597); E, T. tortisquameum (PRA, no. det. 35983); F, T. xanthellum (PRA, T 173); G, T. xiphodon (PRA, T 162). Scale bars: D = 2 mm; A–C, E–G = 5 mm.

FIGURE 36. Taraxacum seminudum. The holotype. Photo M. Hladík.

FIGURE 37. Taraxacum seminudum. A, General habit; B, Achenes (both PRA, no. det. 35973, holotype).