Acantholimon riyatguelii Yıldırım, 2014

Yildirim, Hasan & Crespo, Manuel B., 2014, Acantholimon riyatguelii (Plumbaginaceae), a threatened new unarmed species from Central Anatolia, Turkey, Phytotaxa 175 (2), pp. 73-84 : 74-81

Acantholimon riyatguelii Yıldırım , sp. nov. ( Fig. 1–4 )

Type: — TURKEY. B3 Eskişehir: Sivrihisar , on gypsum soil slopes, 910 m a.s.l., 22 June 2013, Yıldırım 2735 (holotype: EGE-41912!; isotypes: EGE-41913!, ANK!, GAZI!) .

Diagnosis: — Planta notabilis Acantholimonis sect. Staticopsis , omnibus Anatolicis speciebus sectionis distincta et facile distinguitur. Suffrutex inermis , caespitosus, a basi ramosus et valde lignosus. Ramuli brevi, incrassati, carnosuli, diffusi. Folia 3–8 × 1.5–2 mm, omnia conformia, ad apicem ramulorum dense vel laxe rosulata, viridula vel glauca, brevia, tenuia, linearia vel oblongolinearia, mucronata haud pungentia, carnosula, incrassata, tenuiter pilosa praecipue ad margines, calcareo-punctata, versus basin latissime hyalino-vaginantia. Inflorescentia spicata , simplicissima, ad apicem ramulorum solitaria, quam folia valde longior. Scapus 0.8–1.5 cm long., dense puberulentus, 2–3 -squamosus, folia subaequans. Spica 1.5–4 cm long., bene manifesta, dense disticha, folia valde superans. Spiculae 12–14 mm long., numerosae, uniflorae, regulariter imbricatae, internodis brevissimis. Bracteae 3, subaequales, cuspidatae; exterior 6–7 mm long., herbacea, ad margines anguste hyalina, dense pilosa; interiora hyalina nervo rubescente. Calyx 8–10 mm long., infundibuliformis; tubus angustus, 5-costatus, pilosus; limbus albido-scariosus, breviter 5-lobus, nervis haud excurrentibus. Petalis 10–11 mm long., saturate roseis, vix emarginatis. Fructus ca. 5 × 1–1.5 mm, linearis, in parte apicale scabrosulo-papillosus.

Habitat in fruticetibus siccis, solo gypsaceo sicco, loco dicto Sivrihisar ex Anatolia Centrali.

Description:—Dwarf subshrub, laxly caespitose, pale green to glaucous, woody at the base, with several short swollen fleshy branches and strongly developed deep root system. Branches 2–4 cm long, swollen, diffuse, densely leafy at the apex. Leaves 3–8 × 1.5–2 mm, yellowish-green to glaucous, linear to oblong-linear, subterete, fleshy swollen, pilose mostly on margins, mucronate (mucro 0.3–1 mm long), not pungent, calcareous-punctate, dense or laxly rosulate, with a broad hyaline sheath at the base. Scapes 0.8–1.5 cm, densely puberulent, as long as or slightly exceeding leaves, 1-spicate; scales 2–3, hyaline on margins, cuspidate, the lowermost shorter than internodes, the upper ones mostly longer or as long as internodes. Spikes 1.5–4 cm long, densely distichous, much exceeding leaves. Spikelets 7–20, 1-flowered, 12–14 mm long, quite regularly imbricate, all flowers well developed, internodes very short. Bracts subequal, pale green to reddish; outer bract 6–7 mm, ovate, cuspidate, densely pilose, herbaceous in the central part, with broad hyaline margins, as long as calyx tube; inner bracts 5–7 mm, oblong-lanceolate to narrow lanceolate, cuspidate, hyaline with reddish midrib. Calyx 8–10 mm long, infundibular, 5-ribbed, sparsely pilose on ribs; limb 3–4 mm in diameter, whitish-hyaline, with 5 acute lobes; ribs not excurrent, lower half green, upper half reddish; tube 5–7 mm, pilose. Petals 10–11 mm long, purple, slightly notched. Stamens 5; filaments 6–7 mm, white; anthers about 1 mm long, purple. Styles 5, 6– 7 mm long, white. Stigma oblong-elliptic, yellowish. Fruit about 5 × 1–1.5 mm, linear, 5- angled, scabrid-papillose on the upper part. Pollen radially symmetrical, isopolar, prolate-spheroidal to sub-spheroidal, tricolpate; polar length P (52.3–)55.75 ± 0.45(–59.32) µm; equatorial length E (49.1–)53.42 ± 0.28(–54.36) µm. P/E ratio: 1.03. Colpi length (22.25–)25.52 ± 0.48(–28.24) µm long; apocolpium (25.43–)28.34 ± 0.32(–30.13) µm; exine ornamentation reticulate; muri (0.51–)0.78 ± 0.16(–0.92) µm long, lumina (2.03–)2.42 ± 0.41(–2.88) µm wide.

Diagnostic characters:— Acantholimon riyatguelii is easily distinguished by the dwarf caespitose perennial habit (neither forming thorny cushions nor being sturdy subshrubs), the soft and swollen fleshy stem branches, the short, pilose, quite soft and swollen fleshy, mucronate leaves (not long, rigid, usually needle-like and pungent), the long exerted, simple spikes with numerose and dense distichously arranged spikelets, the pilose outer bract of the spikelet, similar in length to the inner ones, the calyces 5-lobed with whitish limb and not excurrent ribs, and the purple corolla ( Fig. 1–4 ). This combination of characters is unique among the Turkish species in the genus, and it therefore warrants easy identification.

Etymology:—Species named honouring Riyat Gül, a very successful amateur Turkish botanist, who first collected the new species.

Habitat and ecology:— Acantholimon riyatguelii grows on deep gypsum-rich soils ( Fig. 2 ), at 900–950 m a.s.l. near Sivrihisar, where it endures hursh climate conditions. According to data from Eskişehir, Sivrihisar and Polatlı weather stations (period 1983−2002, see Erdoğan et al. 2009), summer average maximum temperatures range between 28.9 ºC and 30.5 ºC, whereas winter average minimum temperatures range between -3.4 ºC and -4.6 ºC, frosts being common from November to March. Mean annual average temperature is 11.2 ºC. Total annual precipitation reaches 401.1 mm, and drought period covers from late May to middle September in Sivrihisar ( Böcük et al. 2009). Those data match the Supramediterranean semiarid bioclimatic belt (sensu Rivas-Martínez 2007, Böcük et al. 2009). This peculiar ecological behaviour favours the new species to grow in an isolated position with regard to other representatives of the genus, and this fact has probably contributed to its morphological distinctiveness.

Acantholimon riyatguelii participates in open steppe dwarf-bush communities, together with (taxa marked with an asterisk are endemic to Turkey): Alyssum niveum * T.R. Dudley (1964: 78) , Anthemis cretica Linnaeus (1753: 895) subsp. anatolica ( Boissier 1849: 10) Grierson (1975: 428) (≡ A. anatolica Boiss. ), Arnebia densiflora (Ledebour ex Nordmann 1837: 312) Ledebour (1847: 140) (≡ Lithospermum densiflorum Ledeb. ex Nordm. ), Convolvulus compactus Boissier (1844: 40) , Galium dincii * Yıldırımlı (2012: 46) , Globularia orientalis Linnaeus (1753: 97) , Hedysarum duruae * Yıldırımlı (2012: 21) , Hedysarum hasanyildirimii * Yıldırımlı (2012: 26) , Helianthemum canum ( Linnaeus 1753: 525) Baumgardt (1816: 85) (≡ Cistus canus L.), Linum bienne Miller (1768 : without page), Lomelosia pseudograminifolia ( Huber-Morath 1963: 197) Greuter & Burdet (in Greuter 1985: 75) (≡ Scabiosa pseudograminifolia Hub. -Mor.), Moltkia coerulea ( Willdenow 1798: 775) Lehmann (1817: 6) (≡ Onosma coerulea Willd. ), Plumbago europaea Linnaeus (1753: 151) , and Teucrium polium Linnaeus (1753: 566) , among others.

Biology:—The new species flowers in June, and fruits are released from July. Some of the distinctive morphological traits of A. riyatguelii (e.g., strong development of root system, swollen-fleshy branches, and/or fleshy leaves, pilose mostly on margins) are common around the world to other gypsophilous plants from distant evolutionary lineages (see e.g., Merlo et al. 2011), and they can be interpreted as a result of adaptive selection in stressing gypseous soil. Gypsum directly influences germination and further development of certain gypsophilous plants ( Cañadas et al. 2014), which can finally become dominant specialists in gypseous outcrops. This fact, together with a stressing semiarid climate, has probably conditioned the differentiation of numerous gypsophytes in Central Anatolia, among which the new species is to be counted.

Distribution and biogeography:— Acantholimon riyatguelii is a local endemic restricted to the gypsum outcrops of Sivrihisar in Eskişehir, Central Anatolia ( Fig. 5 ), which together with other representatives of the genus can be regarded as distinctive of the Central-Anatolian province, Irano-Turanian region (see e.g., Zohari 1973, Takhtajan 1986). Gypseous outcrops in that area host a high percentage of narrow endemisms (see e.g., Yıldırımlı 2012), which evolved in such particular climate and soil conditions (see e.g., Erdoğan et al. 2011). Therefore, further prospective effort is to be developed in gypseous areas of the surrounding territories in the cited biogeographical region to locate eventual new populations of the new species.

Taxonomic relationships:— Acantholimon riyatguelii resembles some taxa of A. sect. Staticopsis showing homomorphic leaves and simple long spikes with dense distichously arranged spikelets, such as A. avanosicum Doğan & Akaydın (2002a: 365) , A. confertiflorum Bokhari (1970: 295) , A. karamanicum Akaydın & Doğan (2002: 68) , A. birandii Doğan & Akaydın (2002b: 482) , A. dianthifolium Bokhari (1970: 296) , and A. anatolicum Yıldırımlı (2009: 14) . However, all those species are usually cushion-forming thorny shrubs with subulate pungent long leaves, which at first sight differ considerably from the new species ( Table 1). The unusual habit and leaf features of A. riyatguelii place it apart from all those relatives, probably in a phylogenetically isolate position, and they also warrant easy recognition. Relationships to other Turkish members of the genus are remote.

Acantholimon dianthifolium and A. birandii are also clearly distinguised by the 10-lobed calyx limb, and the glabrous outer bract of the spikelets which is also longer (7–8 mm long). Furthermore, in the former species leaves are broader (1.5–3 mm), the scapes are longer up to 5 cm, the outer bract of the spikelet lacks calcareous-punctate depositions, and the calyx reaches up to 13 mm long, among other characters. In the latter species the spikes are shorter and produce up to 6 spikelets which are smaller (8–8.5 mm long), with also smaller calyces (7–8 mm long). Similarly, A. karamanicum shows smaller spikelets up to 12 mm long, with the outer bract not calcareous-punctate and shortly mucronate, and the corollas are white.

Regarding A. avanosicum and A. confertiflorum , they have 5-lobed calyx limb, and spikelets with the outer bract calcareous-punctate, aristate or cuspidate, similar to those in A. riyatguelii . However, they strongly differ by their subulate leaves lacking calcareous-punctate depositions, the longer scapes up to 7 cm, and the glabrous outer bracts of the spikelets. Additionally, A. avanosicum also shows smaller spikelets with shorter outer bract (4.5–6 mm long), and A. confertiflorum displays longer and narrower leaves (30–50 × 1 mm), and longer calyces 11–12 mm long.

Resemblances to the recently described A. anatolicum , an endemic gypsophyte from NE Anatolia, are weak. Although both taxa share the dense pulvinate glaucous habit and the long exerted spikes, A. anatolicum differs considerably in its overall morphology. It produces linear-triquetrous leaves that are ciliate only on margins and lack calcareous-punctate depositions; scapes are longer and branched, bearing 2–3 shorter spikes, densely congested apically; bracts of the spikelets are unequal, the outer being 4–5 mm long; and the calyx is larger and with 10-lobed limb. According to those obvious differences, probably they belong to different lineages.

karamanicum , and A. anatolicum .

Systematic position:—Turkish taxa of Acantholimon are usually included into three sections (see e.g., Bokhari & Edmondson 1982, Doğan et al. 2003, 2007), on the basis of leaf morphology (homomorphic vs. heteromorphic), inflorescence features (simple vs. branched spike, capitate or congested apically), number of flowers and bracts per spikelet (one vs. several of them), and calyx shape (tubular vs. infundibular). Characters of A. riyatguelii allow inclusion among members of sect. Staticopsis, because the homomorphic leaves, the spicate inflorescence with 1-flowered, 3- bracteate spikelets distichously arranged, and the infundibular calyx.

However, systematic placement of the new species in any of the subsections in current use (sensu Doğan et al. 2007) is problematic. On the basis of numerical taxonomy analyses of 41 morphological characters, Doğan et al. (2007) presented a subsectional rearrangement of sect. Staticopsis, in which five subsections were accepted. Among them, A. subsect. Androsacea Bunge (1872: 38) was defined to include taxa with leaf bases of the previous year not circinate, inflorescence a simple or shortly branched spikes with spikelets densely congested apically, and calyx limb white (Doğan et al. 2007: 89), and therefore it appeared to be a priori the appropriate subsectional taxon to place A. riyatguelii .

Nonetheless, all taxa in that subsection show a very different habit. They are mostly pulvinate cushion-forming subhrubs, with long subulate pungent leaves that lack calcareous-punctate depositions. Provided that A. riyatguelii exhibits morphological features that are unique among the Turkish species, a new subsection is described below to accommodate the new species in A. sect. Staticopsis:

Figures

FIGURE 1. Acantholimon riyatguelii Yıldırım (from Sivrihisar): A. Habit; B. Spikelet; C. Calyx; D. Outer bract; E. Inner bracts; F. Leaves; G. Fragment of the holotype (EGE-41912).

FIGURE 2. Acantholimon riyatguelii Yıldırım: A−F. Habit and habitat (from Sivrihisar, the type locality).

FIGURE 3. Acantholimon riyatguelii Yıldırım: A−C. Branching pattern; D. Flowering spikelet; E. Spikelet dissection; F. Petals with stamens; G. Petals; H. Calyx, showing androecium and gynoecium; I. Calyx at the anthesis; J−K. Spikelet bracts at the anthesis (the outer one on the right side); L. Branchlet with leaves and spike; M−N. Bracts and calyx in fruiting time; O−P. Leaf rossetes; Q−R. Details of leaves, with apical mucro and calcareous-punctate depositions. Scale bars:A−C, L: in cm; D−K, M−N, Q: in mm.

FIGURE 4. Acantholimon riyatguelii Yıldırım:A. Polar view of pollen grain; B. Equatorial view of pollen grain; C. Exine ornamentation; D. Fruit; E. Papillae of fruit apex; F. Detail of fruit papillae.

FIGURE 5. Known distribution of: A. riyatguelii (9-pointed star), A. anatolicum (open circle), A. karamanicum (5-pointed star), A. avasonicum (rhombus), A. confertiflorum (triangle), A. birandii (solid circle), and A. dianthifolium (squares).