Acantholimon subsect. Exacantha Yıldırım & M.B.Crespo, 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 : 81-82

Acantholimon subsect. Exacantha Yıldırım & M.B.Crespo , subsect. nov.

Type: — Acantholimon riyatguelii Yıldırım (holotype).

Diagnosis: — Ex sectione Staticopsi, haec subsectio combinatione insolita characterum ab aliis Anatolicis subsectionibus Acantholimonis diversa suffruticibus inermis , laxe caespitosis; foliis subcarnosis, breve mucronatis haud pungentibus, calcareo-punctatis; caudiculis incrassatis, subcarnosis, foliorum vetustiorum vestigiis persistentibus non circinatis in parte superiore vestitis; spicis longis, simplicissimis, nonnunquam folias valde superantibus; spiculis numerosis, distichis, dense dispositis; bractea exteriore quam rachidis internodio duplo longiore; limbo calycis albido. Species unica: A. riyatguelii .

Taxonomical notes:—The new subsection is related to other groups of A. sect. Staticopsis, e.g. A. subsect. Androsacea and subsect. Caryophyllacea Bunge (1872: 31), with which it shares some characters. Leaves are homomorphic, with remains of leaf bases of the previous year not circinate; inflorescence is a long, simple spike (neither subcapitate nor congested terminally), usually exceeding leaves; the spikelets are dense, distichously arranged, the outer bract being at least twice longer than rachis internodes; and the calyx limb is white. However, the peculiar combination of characters found in the new subsection (e.g., the fleshy, not pungent and calcareous-punctate leaves, the swollen fleshy branchlets, and the long exerted spikes) makes it to stand apart from all other subsectional taxa in A. sect. Staticopsis.

Certainly, simple and elongated spikes also occur in members of A. subsect. Caryophyllacea, though spikelets are more laxly arranged, the outer bract equalling or being at most 1.5 times longer than rachis internodes. Furthermore, members of A. subsect. Androsacea produce 1–2-branched (occassionally simple) usually short spikes, with rather dense spikelets, imbricate or congested apically.

Segregation of the new subsection from members of A. subsect. Robusta Doğan & Akaydın in Doğan et al. (2007: 87) and subsect. Circinata Doğan & Akaydın in Doğan et al. (2007: 88) is based on the occurrence of circinate base remains of leaves of the previous year, which are absent in taxa of A. subsect. Exacantha, among other characters. Similarly, the monotypic A. subsect. Dianthifolia Doğan & Akaydın in Doğan et al. (2007: 88) includes plants easy to recognize because their linear-lanceolate flat leaves, the scapes usually lacking scales, the inner bracts of the spikelets retuse-mucronate, and the calyx with excurrent ribs.

Nonetheless, the peculiar morphological characters of A. riyatguelii put it apart from the rest of members of sect. Staticopsis, and in the future it could be placed in its own section. Ongoing preliminar molecular work ( Crespo et al. in prep.) supports separation of A. riyatguelii , and will help to clarify the phylogenetic relationships of this outstanding new taxon..

Conservation status:—The occupancy area (AOO) of A. riyatguelii was calculated as 0.683 km 2 in which about 750−850 individuals were estimated to occur. Overgrazing by sheep and goat herds and development of new farming areas were observed to be producing negative effects on the surroundings of the known populations, which are seriously threatened as well as other similar habitats in Central Anatolia ( Böcük et al. 2009). These strong anthropic pressures on this new gypsophyte are responsible for rapid habitat destruction, and they could cause a dramatic decrease of the number of reproductive individuals in the near future. Therefore, in accordance with the criteria of the IUCN (2012), A. riyatguelii is here assessed as “Critically Endangered” (CR) B2ab(i,ii,iii), on account of its restricted distribution in Turkey with an inferred severe decline of the extent of occurrence, the occupancy area and quality of the habitat. In consequence, this new Irano-Turanian element stands among other Turkish threatened endemic taxa of Acantholimon (cfr. Doğan et al. 2011).

Urgent legal measures should be implemented to ensure conservation of A. riyatguelii , which should be included in the red list of Turkish vascular plants. Similarly, the habitat in which it grows should also be protected, since gypseous outcrops of Central Anatolia host a remarkable phytodiversity with a high number of narrow endemics (cfr. Yıldırımlı 2012) in need of conservation.