Hieracium sourekii Szeląg, 2025

Szeląg, Zbigniew, 2025, Hieracium sourekii (Asteraceae), a new species in the H. senescens aggregate and the discovery of H. subortum in the Sudetes, Poland, Phytotaxa 696 (3), pp. 217-223 : 217-220

Hieracium sourekii Szeląg , sp. nov. ( Figs. 1–3 )

Type: ― POLAND. Sudetes , Karkonosze Mts., Biały Jar glacial niche, eroded porphyry rocks with Pinus mugo , 1270 m a.s.l., 4.07.1992, Z. Szeląg (holotype KRAM; isotypes Herb. Hierac. Z. Szeląg) .

Paratypes: ― POLAND. Sudetes, Karkonosze Mts., Biały Jar glacial niche, eroded porphyry rocks, 1310 m a.s.l., originally found on July 25, 2020, specimens from plants cultivated from seed in the author’s garden, pressed on June 5, 2024, Z. Szeląg (Herb. Hierac. Z. Szeląg).

Description: ―Phyllopodous. Stem 20–35 cm high, robust, in the lower third with scattered pale simple hairs 1–2 mm long, sparse stellate hairs and few pale microglands; in middle part with sparse dark-based simple hairs up to 2 mm long, numerous stellate hairs and numerous black glandular hairs 0.3–0.6 mm long; within synflorescence with sparse, dark-based simple hairs 1–1.5 mm long, subdense stellate hairs, and dense, black glandular hairs up to 1.2 mm long. Synflorescence branches 1–2 (in cultivation 3–5 in axils of all cauline leaves), up to 13 cm long, with 1–3 capitula. Acladium 3–5 cm long. Rosette leaves 8–12, up to 10(–12) cm long and up to 3 cm wide, cuneate at base, tapered to a long petiole, glaucous-green and somewhat coriaceous; outer leaves obovate, remotely denticulate and dentate at base, rounded at apex; inner leaves oblanceolate, sharply dentate or serrate at base, acute at apex; on upper surface with numerous 0.5–1.2 mm long trichomes and with sparse stellate hairs along the midrib; on margins with numerous stiff trichomes up to 1.5 mm long and sparse glandular hairs; on lower surface with scattered to numerous trichomes up to 1.0 mm long, on midrib with numerous trichomes up to 1.5 mm long and scattered, pale glandular hairs. Cauline leaves 1–3 sessile, lanceolate, entire, up to 3 cm long, acute at apex; on upper surface with sparse, pale trichomes 0.5–0.7 mm long; on lower surface with numerous, dark-based trichomes up to 1.5 mm long; on midrib mixed with sparse, blackish glandular hairs. Peduncles with few, dark-based simple hairs 1.0– 1.5 mm long, dense stellate hairs, and very dense, black glandular hairs 0.6–1.2 mm long. Bracteoles 1–3, separate from capitula. Involucres 10–11 mm long, subglobose at base with dense indumentum. Involucral bracts dark green with blackish midrib, lanceolate, acute at apex, with rather dense, black in lower half simple hairs up to 1.5 mm long, and quite dense blackish glandular hairs 0.5–1.1 mm long (without stellate hairs). Ligules yellow, with numerous cilia at apex. Styles yellow (dirty-yellow when dried). Achenes black, 3.1–3.4 mm long. Pappus pale grey. Pollen sparse, spherical and of varying size. Flowering in July.

Chromosome number and mode of reproduction: —2n = 3x = 27, agamospermous (Grabowska-Joachimiak & Szeląg, unpubl.).

Distribution and habitat: —Endemic to the Karkonosze Mountains in the Sudetes, known only from the Biały Jar glacial niche. In 2023, the population of H. sourekii comprised not more than 40 plants, growing on eroded porphyry rocks, amongst the loose thickets of Pinus mugo ( Fig. 5 ), together with H. subortum , at 1250–1320 m a.s.l.

The population of H. sourekii has decreased compared to 1992, when I first found it. The main reason of the decline is the habitat destruction by tourists visiting this place in the summer season. The succession of Deschampsia caespitosa and Pinus mugo is also a threat, leading to the decline of many mountain grassland plants in the Karkonosze Mountains ( Grulich 2017).

Etymology: —The species is named in honour of Josef Šourek (1891–1968), Czech botanist, retired colonel of the former Czechoslovak army, a brave man and faithful to his ideals at the time when this was not common ( Procházka 2002). He wrote the Flora of the Giant Mountains where he made many significant floristic discoveries ( Šourek 1970).

Affinity: —In general habit Hieracium sourekii is similar to H. atratum s.lat. but differs in the glaucous, somewhat coriaceous leaves, smaller capitula, yellow styles, and smaller cauline leaves. They differ also karyologically; H. atratum s.lat., despite its high morphological diversity in the Karkonosze Mountains, is represented here by only tetraploid taxa ( Musiał et al. 2024).

Discussion: —It is very likely that H. sourekii has originated in situ as a result of hybridization between the local populations of H. alpinum and H. subortum . As no diploid populations of H. alpinum , much less H. subortum , are currently known in the Sudetes, it is most likely that H. sourekii is a relict species (like a number of other hybridogenous Hieracium taxa in the Sudetes) which originated when sexual populations of H. alpinum occurred here as well.

Hieracium subortum is endemic to the Karkonosze Mountains, previously only known from two localities in the Czech side of the mountains where it has not been collected for over a hundred years ( Zahn 1935; Šourek 1970). The new locality in the Biały Jar glacial niche is the first on the Polish side of the mountains where it was discovered in 1992. In 2023, the population of H. subrotrum comprised at least 130–150 flowering and numerous vegetative plants spread over about two hectares, both above and below the tourist road, at 1180–1370 m a.s.l.

Schneider (1894) considered H. subortum as morphologically intermediate between two taxa of the H. schmidtii aggregate, i.e. H. rupicolum ( Fries 1850: 96) and H. schmidtii . Zahn (1935) included it in the H. glaucinum aggregate comprising taxa intermediate morphologically between H. murorum s.lat. and H. schmidtii . In a recent publication, H. subortum is listed as a synonym of H. glaucinum Jordan (1848: 22) which means it has been somewhat overlooked ( Chrtek 2004).

I have searched for the original material of H. subortum in the main Central European herbaria, including the herbarium of the Wrocław University (WRSL) where the Sudetic collection of Gustav Schneider is held, but have not so far traced any. Therefore I designate a neotype for H. subortum from specimens collected in the Biały Jar glacial niche to help with interpretation of the species.

Figures

FIGURE 1. Holotype of Hieracium sourekii (KRAM).

FIGURE 2. Hieracium sourekii in cultivation (rosette, capitula).

FIGURE 3. Involucres of Hieracium sourekii (left) and H. subortum (right) (from holotypes).

FIGURE 5. Habitat of Hieracium sourekii and H. subortum in the Biały Jar glacial niche.