Centaurea ziganensis Yuezb ., M. Bona & I . Genc, 2015

Yuezbasioglu, Ibrahim Sirri, Bona, Mehmet & Genc, Ilker, 2015, A new species of Centaurea sect. Pseudoseridia (Asteraceae) from north-eastern Turkey, PhytoKeys 53, pp. 27-38 : 29-31

Centaurea ziganensis Yuezb., M. Bona & I. Genc sp. nov. Fig. 1

Diagnosis.

Centaurea ziganensis is related to Centaurea drabifolioides , from which it differs mainly in its 2-4 (-8) branched and non-winged stem (not simple and winged), median phyllary appendages with 4-6 pairs of cilia (not 5-10); achenes 4.5-5 mm long, oblong, straw-colored, striate (not 5.5-6 mm long, lanceolate, blackish-chestnut, shiny); pappus straw-colored (not blackish-chestnut).

Type.

TURKEY. Gümüşhane: Zigana pass-Gümüşhane road, c. 5. km, rocky places, 1450 m a.s.l., 20 Aug 2014, S. Yüzbaşıoğlu 4117 (holotype: ISTE 104470, isotype: ANK).

Description.

Perennial herb with sterile leaf-rosettes and woody rootstock. Stems erect or erect-ascending, pubescent with short simple hairs, 30-70 cm long, not winged, usually 2-4 (-8) well developed one-headed branched from near middle. Basal leaves scabrid with multiseriate septate hairs, and densely covered transparent sessile glands on both surfaces, narrowly lanceolate, petiole 3.5-6.5 cm long, margins entire or sparsely toothed, c. 10 teeth on each side (c. 1 mm long), acute, attenuate, 10-20 × 0.5-1.5 cm (inc. petiole). Median and upper cauline leaves scabrid, linear-lanceolate, mucronate (c. 1 mm) at apex, margins entire; the median ones 5-10.5 × 0.8-1 cm, distinctly decurrent; the upper ones 1.2-3.5 × 0.2-0.4 cm, sessile, not decurrent, leaves decreasing to capitula, uppermost bract-like. Capitula 2-4 (-8), solitary at end of well-developed branches. Involucre ovoid, 15-20 × 12-15 (-18) mm. Phyllaries green, tomentose at apex; the outer ones ovate, 5-6 × 4-5.2 mm; the median ones lanceolate, 9.5-10 × 4.6-5 mm; innermost linear-lanceolate, 16-17 × 3.2-4 mm. Appendages small, not concealing basal part of phyllaries, 1.5-2 mm broad, dark brown, triangular, not decurrent, spreading or reflexed, with 4-6 pairs of cilia (1-3 mm), ending with a 2 -4 mm spinule. Florets yellow, marginal not radiant; corolla tube glabrous, 20 mm long, lobes 6-7 × 0.5 mm, linear, with 5 brown stripes along corolla tubes; anthers 10 mm, filaments 4 mm long. Achenes oblong, straw-coloured, glabrous, distinctly striate, 4.5-5 × 2-2.2 mm; pappus straw-coloured, biseriate, scabrous, outer series 5.3-6.2 mm long, inner series 1.5-1.8 mm long.

Phenology.

Centaurea ziganensis flowers from the end of June to-July, and mature fruits are produced in August-early September.

Etymology.

Named after the Zigana Mountains where it was discovered.

Ecology.

The new species was only found on the southern slopes of Zigana Mountains and occurs on rocky slopes at c. 1500 m elevation. Within this area, the new taxon is associated with plants such as: Allium rupestre Steven, Alyssoides utriculata (L.) Medik., Arenaria serpyllifolia L., Asplenium septentrionale (L.) Hoffm., Asyneuma lobelioides (Willd) Hand.-Mazz., Berberis vulgaris L., Campanula betulifolia C. Koch, Coronilla orientalis Mill. var. orientalis , Euphorbia condylocarpa M. Bieb., Fibigia clypeata (L.) Medik., Haplophyllum armenum Spach, Helianthemun nummularium (L.) Mill., Hypericum pruinatum Boiss. & Bal., Hyssopus officinalis L. subsp. officinalis , Juniperus oxycedrus L. subsp. oxycedrus , Lamium galactophyllum Boiss. & Reuter, Laser trilobum (L.) Borkh., Ornithogalum narbonense L, Psephellus pyrrhoblepharus (Boiss.) Wagenitz, Reichardia glauca Matthews, Rosa canina L., Salvia tomentosa Mill., Salvia verticillata L., Saxifraga paniculata Mill., Sempervivum transcaucasicum Muirhead, Silene dichotoma Ehrh. subsp. sibthorpiana (Reichb.) Rech., Sobolewskia clavata Fenzl, Teucrium polium L. and species of Acer and Quercus .

Distribution and proposed conservation status.

As presently known, Centaurea ziganensis is a narrow endemic and known only from the type locality, north eastern Anatolia ( Gümüşhane): where the extent of occurrence is less than 100 km2 (criterion B1), with an estimated area of occupancy of less than 10 km2 (criterion B2). According to our field observations, habitat destruction through human encroachment such as road construction is the principal threat in the area. Therefore, on the basis of our knowledge, we argue that the species is potentially Critically Endangered (CR), but more data are needed to estimate its real IUCN category of threat ( IUCN 2014).

Karyology.

The chromosome number of the new taxon is 2n = 18 (Fig. 2a ). The shortest chromosome length is 2.22 µm, the longest is 3.55 µm, and the haploid chromosome length is 24.17 µm. The karyotype formula of this taxon consists of 10 median pairs and 8 submedian pairs. Satellites were usually seen on the short arms of the longest sub-metacentric chromosomes. As for karyotype asymmetry, the karyotype of this species is classified according to the symmetry classes of Stebbins as 3A. Intrachromosomal asymmetry (MCA) is 20.90 and the interchromosomal asymmetry index (CVCL) is 16.32. The karyogram is given in Figure 2b , and ideogram was drawn based on the centromeric index (Fig. 2c ).

Our study showed that the chromosome number of Centaurea drabifolioides Hub.-Mor. is 2n = 18 (Fig. 2d ). The shortest chromosome length is 1.51 µm, the longest is 2.77 µm, and the haploid chromosome length is 18.64 µm. The karyotype formula of this taxon consists of 10 median pairs and 8 submedian pairs. Satellites were usually seen on the short arms of shortest sub-metacentric chromosomes. As for karyotype asymmetry, the karyotype of this species is classified according to the symmetry classes of Stebbins as 3A. Intrachromosomal asymmetry (MCA) is 22.71 and the interchromosomal asymmetry index (CVCL) is 17.95. The karyogram is given in Figure 2e , and ideogram was drawn based on the centromeric index (Fig. 2f ).

SEM observations.

Seed surface pattern of Centaurea ziganensis is ruminate. Testa cells are regularly arranged, elongated parallel with the seed surface and the cells are apparently imbricate. The cell boundaries are thin and have smooth structure, and the boundaries raised above cell centre (Fig. 3a-c ). Even seed surface pattern and testa cell arrangement of Centaurea drabifolioides are similar to Centaurea ziganensis , the cell centres raised above the boundaries and testa cells are not apparently imbricate (Fig. 3d-f ).

Figures

Figure 1. Centaurea ziganensis sp. nov. a habit b roset leaves c achene d median phyllaries e capitulum.

Figure 2. Somatic chromosomes, karyotype and idiogram of Centaurea ziganensis (a-c); Centaurea drabifolioides (d-f). Arrow indicates satellite. Scale bars = 5 µm.

Figure 3. Scanning electron micrographs of achene surface. (a-c) Centaurea ziganensis. (d-f) Centaurea drabifolioides.