Taraxacum tilesianum Kirschner & Štěpánek, 2023

Kirschner, Jan & Štěpánek, Jan, 2023, A taxonomic revision of Taraxacum sect. Dissecta, a continental steppe group common in Siberia and adjacent regions of Central Asia, Phytotaxa 590 (1), pp. 1921-1935 : 1921-1935

7. Taraxacum tilesianum Kirschner & Štěpánek , sp. nov.

Type:—[ RUSSIA, Irkutskaya oblast] 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 2600 ( PRA, no. det. 35965, holotype; isotype: PRA, no. det. 35969) .

Etymology:—Named after the famous biologist and traveller, W. G. Tilesius von Tilenau, 1769–1857.

Diagnosis:—Plantae foliis glabrescentibus dissectissimis, segmentis foliorum lateralibus linearibus vel lineari-lingulatis angustissimis, interlobiis acute lobulatis et dentibus filiformibus praeditis, phyllariis involucralibus exterioribus adpressis, ovatis vel ovatolanceolatis, aequabiliter obscure viridibus, marginibus fere invisibilibus membranaceis usque ad 0.1 mm latis, acheniis pallide griseo-stramineis, superne saepe rubescentibus, corpore breviter spinuloso, in pyramidem subcylindricam 0.5–0.7 mm longam sensim transeunte.

Plants small, usually to 12 cm tall. Petiole narrow, unwinged, green or ± purplish, subglabrous to very sparsely arachnoid; plant base with tunic, with brownish hairs. Leaves mid-green to greyish green, subglabrous, oblong-linear or linear-oblanceolate in outline, usually 5–9.5 × 1–2.4 cm, deeply dissected into ± linear, acuminate lateral segments and lobulate-dentate interlobes, lateral segments usually 4–6 pairs, linear to linear-lingulate, usually 5–11 mm long, ca. 1–1.3 mm wide in the middle, acute to acuminate, distal margin ± straight to subconcave, sometimes ± dilated at base, often with 1–2 acuminate lobules at base, proximal margin ± straight, entire; terminal lobe tripartite, with short, linear distal lobe and basal lobules; interlobes with acuminate lobules and usually also with a few filiform teeth, dark bordered; mid-vein slightly purplish or light green. Scapes arachnoid, usually brownish green, usually overtopping leaves. Capitulum yellow, usually 2–3 cm wide. Involucre dark green, usually 9–10 mm wide and broadly rounded to subtruncate at base. Outer phyllaries most often 12–15, appressed, subimbricate to not imbricate, ovate to ovatelanceolate, often quite abruptly narrowed in an acuminate tip, usually (6.0–) 6.5–8.5 × (2.5–) 3–3.5 mm, surface evenly dark (± greyish) green, often darker and suffused purplish near apex, border absent or almost invisible, membranous, ca. 0.1 mm wide, margin not ciliate, glabrous, apex ± flat; inner phyllaries 12–14 mm long, flat. Outer ligules flat, striped purplish grey outside, inner ligule teeth ± grey. Stigmas light discoloured, pale greyish yellow or pale greenish yellow, sometimes with sparse greyish pubescence outside. Pollen present, pollen grains irregular in size. Achenes light grey, often distally with pinkish hue, usually 3.5–4.0 × 0.8–0.9 mm, body subsparsely covered with short erectpatent spinules in upper 1/4 (some spinules often on basal part of the cone), gradually narrowing into a subcylindrical cone 0.5–0.7 × 0.3 mm; beak 7–7.5 mm long, pappus white, ca. 5 mm long. – Agamosperm. – Fig. 8 .

Diagnostic notes:—A combination of ± glabrous, deeply dissected leaves with numerous acute linear lobes and lobules, the borderless glabrous outer phyllaries, and greyish (distally often pinkish) achenes with a body very gradually narrowing into a short cone, clearly distinguishes T. tilesianum from the other members of the section Dissecta .

Distribution and ecology:—Known from a single macrolocality situated along the shore of the Bratsk reservoir on the Angara River, at about 400 m a.s.l. It grows on gravelly and sandy open places and adjacent grasslands.

Specimens examined:—[ RUSSIA, Irkutskaya oblast] 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 2600 ( PRA, no. det. 35969, with duplicates). – Ibidem, cultivated as JŠ 2599 ( PRA, no. det. 36711) .

Figures

FIGURE 8. Taraxacum tilesianum. A, General habit; B, Achenes (both from PRA, no. det. 35969).