Taraxacum (sect. Obliqua) Dahlstedt 1921
Creators: name: Štěpánek, Jan
name: Kirschner, Jan
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Asterales
Asteraceae
Taraxacum

description: A.  Taraxacum sect. Obliqua  (Dahlstedt 1909: 172) Dahlstedt (1921: 37)   
 ≡ Taraxacum [unranked] Obliqua Dahlstedt (1909: 172)   
 ≡ Taraxacum subsect. Obliqua (Dahlst.) Schischkin (1964: 493)   
 Type:— Taraxacum obliquum (Fries 1814: 14) V. Strøm & Lange (1840: 403)   
 ≡ Leontodon taraxacum subsp. obliquum Fries (1814: 14)   
 Type:—[protologue indication: In littore marino ad Halmstad] [Sweden, Halmstad] Hallandia ad Snöstorp copiose [scripsit E. Fries], sine dato (LD 1019268!, lectotype, designated by C. F. Lundevall & H. Øllgaard in Kirschner & Štěpánek 1997: 94).    Introduction   
 The name T. sect. Obliqua was introduced to include two species, T. obliquum and T. platyglossum Raunkiaer (1906: 139), two distinctive coastal agamospermous taxa, and this conception has been almost unanimously accepted in the modern literature (Wendt & Øllgaard 2015). We recognized a remarkable Pyrenean sexual, T. pyrenaicum Reuter (1861: 4), as the core taxon of a group of species that are extremely similar to T. obliquum, and the whole T. pyrenaicum group was therefore included in T. sect. Obliqua (Kirschner et al. 2015; Sahlin 1984a). Taraxacum pyrenaicum is a conspicuous subalpine species in the eastern Pyrenees and there are several agamospermous species in the southeastern Alps and the Alpes Maritimes, obviously closely allied to it [e.g., T. lambinonii van Soest (1961: 289), T. marmottae Sonck (1990: 272), T. artificis Sonck (1998: 175)]. Recently, J. Štěpánek (unpubl.) revealed and collected plants almost identical with T. pyrenaicum in the Central Apennines; their local allies remain unexplored at present. Last, a detailed study of Taraxacum in the mountains of Bulgaria revealed another sexual taxon, also referable to T. sect. Obliqua; there are a few closely related agamospermous species treated as members of this section in the present study. The broadly understood T. sect. Obliqua therefore is a predominantly Oreo-Mediterranean group occurring in the Pyrenees, southwestern Alps, the Alpes Maritimers, central Apennines and mountains of Bulgaria, with two coastal dealpine agamospermous species extending to the western and northwestern Europe. The Bulgarian species occupy habitats similar to those of T. pyrenaicum subsp. pyrenaicum: wet alpine grasslands, open patches in subalpine and alpine meadows.   
A combination of diagnostic features includes a peculiar growth (a many-headed root system with very numerous leaves forming cushions, less distinctive in hybridogenous agamospermous derivatives of the sexual species), usually almost glabrous leaves with greenish petiole and numerous lateral segments, usually glabrous scapes, outer phyllaries appressed to regularly erect-patent, ovate-lanceolate to narrowly lanceolate, usually evenly (light to dark) green, borders absent or narrow, whitish green, apex often abruptly bent inwards, „humped“, stigmas most often yellow to very light discoloured, and achenes light stramineous-brown, ± sparsely spinulose, with body ± sparsely spinulose above, ± abruptly narrowing in a short, conical to subconical cone.   Description   
Plants small, rarely medium-sized, roots often many-headed (plants cushion-forming), often also single-headed, plant base with or without tunic, leaf rosettes of well developed plants with many, often prostrate leaves. Leaves usually narrowly oblong to oblong-oblanceolate in outline, relatively light green, not spotted, glabrous or glabrescent, pinnatisect or pinnatipartite, with (4) 6–7 pairs of patent, subrecurved or ± hamate, usually narrowly triangular to narrowly triangular-hamate lateral segments, margins entire or denticulate, apex obtusely acute to acute; interlobes usually short, often dentate; mid-vein pale green or proximally suffused pinkish (not longitudinally purplish striate); petiole usually unwinged or narrowly winged, green, sometimes purplish. Scapes ± equalling or slightly overtopping leaves, glabrous, or arachnoid and later glabrescent. Capitulum small to medium wide, yellow to deep golden yellow, ligules canaliculate to flat, striped pale purple or pale brown-purple. Involucre green to olivaceous-green, ± rounded or subobconical at base. Outer phyllaries relatively numerous (usually 12–19), appressed, loosely appressed or erectpatent, not imbricate or subimbricate, short, often shorter than 1/2 of inner phyllaries, light green, mid-green or deep green, sometimes suffused reddish distally or on margins, paler border almost absent or inconspicuous, narrow, whitish, but in some agamospermous species relatively broad, margin often minutely ciliate, apex seemingly corniculate or callose, in reality the apex is abruptly curved towards inner phyllaries, as if humped, with the „hump“ often carinate swollen, rarely flat. Stigmas usually yellow, golden yellow or very light discoloured (also discoloured outside Bulgaria). Achenes light stramineous-brown, in some species slightly reddish, medium-sized, usually to 4 mm long (of ± variable length in sexual species), body with sparse to subdense minute spinules above, most often subabruptly or ± abruptly, less often subgradually narrowing into a short, usually 0.3–0.7 mm, sometimes to ca. 1 mm long, conical to subconical cone; beak thin, 3–7 mm long, rarely longer; pappus ± white.  
 Taraxacum sect. Obliqua includes about 15 species and subspecies distributed in the mountains of southern Europe (the Pyrenees, SW. Alps and their promontories in France, Apennines, and Bulgarian mountains). Two species occupy coastal habitats in western and northwestern Europe. In each of the main diversity centres, there are sexual populations.   
The Bulgarian members of this section do not deviate substantially from the above diagnostic pattern, perhaps with the exception of more common winged petioles. A comparison of the Bulgarian species is given in Table 3.   Selected, verified members of T. sect. Obliqua   
 Taraxacum artificis Sonck (1998: 175)   
 Taraxacum benevolens, sp. nov.   
 Taraxacum blandum, sp. nov.   
 Taraxacum caespitosum van Soest (1976: 173)   
 Taraxacum dissectiforme van Soest (1977: 141)   
 Taraxacum chrysocephalum, sp. nov.   
 Taraxacum lambinonii van Soest (1961: 289)   
 Taraxacum marmottae Sonck (1990: 272)   
 Taraxacum obliquum (Fries 1814: 14) Dahlstedt (1905: 152)   
 Taraxacum platyglossum Raunkiaer (1906: 139)   
 Taraxacum pyrenaicum Reuter (1861: 4)   
 subsp. pyrenaicum (syn.: T. andorriense Sahlin 1984a: 113)   
 subsp. balcanicum, sub sp. nov.   
 Taraxacum sordidepapposum van Soest in Kirschner & Štěpánek (2014: 177)    An identification key to the Bulgarian members of T. sect. Obliqua   
 1 Pollen grains regular, of ± uniform size.............................................................. 1. T. pyrenaicum subsp. balcanicum, subsp. nov.   
– Pollen grains irregular, of conspicuously variable size, or pollen absent......................................................................................... 2  
 2 Pollen absent; cone 0.4–0.7 mm long; most leaves prostrate, appressed to the ground................................ 4. T. blandum, sp. nov.   
– Pollen present; cone usually 0.7–1.0 mm long; most leaves erect-patent or patent; some leaves prostrate.................................... 3  
 3 Beak 4.5–6 mm long; outer phyllaries with an abrupt transition between the middle part and a narrow membranous border ca. 0.1 mm wide; scapes ± glabrous; involucre not pruinose................................................................................ 3. T. benevolens, sp. nov.   
 – Beak 6.5–8.5 mm long; outer phyllaries with a ± gradual transition between the middle part and a whitish border 0.2–0.6 mm wide; scapes sparsely arachnoid; involucre pruinose................................................................................. 2. T. chrysocephalum, sp. nov.
description: Published as part of Štěpánek, Jan & Kirschner, Jan, 2022, A hotspot of endemism: Oreophytic Taraxacum species (Compositae, Crepidinae) in the mountains of Bulgaria, pp. 1-139 in Phytotaxa 569 (1) on pages 16-18, DOI: 10.11646/phytotaxa.569.1.1, http://zenodo.org/record/7235182