Introduction

Turkey, with about 10 150 vascular plant species (Dönmez & Yerli in press), is one of the richer countries in terms of plant biodiversity. It is likely that the Turkish flora still has many undiscovered plant species, especially in the less botanized areas, such as the southeast of the country. Among the vascular plants of Turkey, Astragalus L. (Fabaceae) is the largest genus, with 444 species representing 3.8 % of the vascular plant species of the country (Dönmez & Yerli in press). Furthermore, 197 Astragalus species were recorded as endemic to Turkey by Chamberlain & Matthews (1970).

According to the recent most comprehensive revision of the genus (Podlech & Zarre 2013), Astragalus has 2950 species and is the largest genus of flowering plants in the world. Since the publication of this three-volume monographic study for the Old World, several new species have been described from Turkey (e.g. Dinç & al. 2013; Karaman Erkul & Aytaç 2013; Çeçen & al. 2016) as well other countries (e.g. Li & Yu 2014; Estrada Castillón & al. 2016; Bagheri & al. 2017), and discovery of new taxa of Astragalus will no doubt continue.

The number of species of Astragalus sect. Incani DC. was given by Podlech & Zarre (2013) as 140, and 22 species were listed by Chamberlain & Mathews (1970) under the name A. sect. Proselius Bunge for the Turkish flora. Based on the taxonomic and nomenclatural changes for the section and additionally the description of new species and new records according to Podlech & Zarre (2013), 36 species are now known to occur in Turkey.

During one of our botanical expeditions to SE Turkey in 2015, an unusual specimen of Astragalus was collected and photographed in Erzurum province. Subsequently, our studies showed its resemblance to specimens of A. glaucophyllus Bunge (1868, 1869) and A. guzelsuensis F. Ghahrem. & al. (Ghahremaninejad & al. 2009) from Turkey as well as A. siahcheshmehensis Maassoumi & Podlech (2003) from Iran. To observe population size and collect seeds, the type locality was re-visited in 2018. After further research on the relevant literature and comparison with herbarium material of the species mentioned above, we recognized that our specimens from Erzurum province represent a species of Astragalus new to science.

Material and methods

The morphological description of the new species was prepared based on the type material collected by the first author from Erzurum province. Material was examined in the herbaria GAZI, HUB and, by means of the JSTOR Global Plants database (JSTOR 2018), B, E, G, MSB, P and W (herbarium codes according to Thiers 2018+). We used a binocular stereoscopic microscope (SM) for detailed examination of indumentum and other fine structures. We also used a Zeiss EVO 50 EP scanning electron microscope (SEM) to create micrographs of surface details of leaflets, bracts and legumes, pieces of which were mounted directly onto stubs and coated with a gold-palladium mixture. Conservation status of the new species was assessed based on field observations and IUCN (2012, 2017) criteria.

Results

Astragalus ihsancalisii Dönmez & Uğurlu, sp. nov. [A. sect. Incani DC.] – Fig. 1, 2A – D, M, N.

Holotype: Turkey, A8 Erzurum, Horasan, 1 km from road junction of İğdeli village to Eleşkirt, 1795 m, 39°56′31″N, 42°19′49″E, 26 Jun 2015, A. A. Dönmez 19559 (HUB!; isotypes: B!, GAZI!, HUB!). – Paratypes: same locality, 14 Jul 2018, A. A. Dönmez 20160, Z. Uğurlu & S. Yüzbaşioğlu (HUB!, ISTE!); same locality, 14 Jul 2018, Z. Uğurlu 599, A. A. Dönmez & S. Yüzbaşioğlu (HUB!).

Diagnosis — Astragalus ihsancalisii is similar to A. glaucophyllus Bunge, A. guzelsuensis F. Ghahrem. & al. and A. siahcheshmehensis Maassoumi & Podlech. The new species differs from A. glaucophyllus by having fewer flowers per raceme (3 – 6 vs 8 – 15 to many), shorter bracts (2 – 3 mm vs 5 – 7 mm), longer pedicels (4 – 6 mm vs 3 – 4 mm) and a distinctly stipitate ovary and legume (legume stipe c. 1 mm long vs absent). The new species differs from A. guzelsuensis by having fewer flowers per raceme (3 – 6 vs 4 – 12), shorter bracts (2 – 3 mm vs 4 – 5 mm), longer pedicels (4 – 6 mm vs 2.5 – 3 mm), a shorter standard (20 – 23 mm vs 29 – 31 mm) and a longer legume beak (4 – 5 mm vs 2 – 2.5 mm). The new species differs from A. siahcheshmehensis by having a shorter standard (20 – 23 mm vs c. 25 mm), a longer keel (18 – 20 mm vs c. 17 mm) and a longer legume beak (4 – 5 mm vs 1 – 2(– 3) mm).

Description — Plants 10 – 20 cm tall, caespitose, with a woody caudex enclosed in remains of old stipules and petioles. Rootstock 6 – 8 mm in diam. Stipules adnate to petiole for 1 – 2 mm, triangular to lanceolate, 2 – 5 × (1 –)2 – 3 mm, hard papery, mostly white bifurcate hairy outside, with few hairs inside. Leaves 6 – 12 cm long; petiole purple-flushed, 2 – 3 cm long, narrowly grooved adaxially, sparsely white bifurcate hairy throughout. Leaflets in 5 – 8 pairs, glaucous, broadly elliptic to suborbicular, 8 – 12 × 6 – 8 mm, sparsely to loosely bifurcate hairy abaxially, glabrous or with few hairs along midrib adaxially, rounded to obtuse at apex. Peduncle arcuate ascending, slender, 5 – 8 cm long, finely striate throughout, sparsely covered with white (rarely a few black) hairs proximally. Raceme 3 – 6-flowered, later elongating up to 2 cm; axis mostly with black hairs. Bracts narrowly triangular to lanceolate, 2 – 3 × 1.5 – 2 mm, with subsessile minute glands, with white and few black hairs at margin, scarious at margin, obtuse to acute at apex. Bracteoles in a pair at base of calyx, subulate, 1 – 1.5 mm long. Pedicel 4 – 6 mm long, white and black hairy. Calyx tubular, oblique at mouth, 9 – 12 mm long, loosely covered with appressed mostly black hairs; teeth subulate, 2 – 3(– 3.5) mm long, sparsely hairy on inner side. Corolla purple to violet. Standard 20 – 23 mm long; limb straight, obovate, 6 – 8 mm wide, obtuse to slightly emarginate at apex. Wings 19 – 22 mm long; limb narrowly oblong, 9 – 11 × 2 – 2.5 mm, slightly emarginate and obtuse at apex; auricle 1.3 – 1.6 mm long; claw 9 – 11 mm long. Keel 18 – 20 mm long; limb obliquely elliptic-curved with widely curved lower edge and concave upper edge, 6 – 8 × 3 – 3.5 mm, obtuse at apex; auricle c. 1 mm long; claw 9 – 11 mm long. Stamen tube 10 – 12 mm long, truncate at mouth. Ovary stipitate, linear, glabrous; style 10 – 11 mm long. Legume erect, linear, straight or slightly curved, slightly flat, 20 – 35 × 3 – 4 mm, keeled abaxially and adaxially, fully bilocular, with a stipe c. 1 mm long at base, gradually contracted into a straight 4 – 5 mm long beak at apex; valves purplish to straw-coloured, irregularly purplish mottled, thick and tenacious, glabrous. Seeds 6 – 9 in each locule, brown, oblong-reniform to deltoid, 3 – 4 × 1.5 – 2.2 mm, smooth.

Phenology — Flowering in June; fruiting in July and August.

Distribution and ecology — The new species is an Irano-Turanian element currently known only from the type locality in the eroded hills of Horasan in Erzurum province, E Turkey. The habitat of the species is a semi-desert steppe with weak vegetation cover. Dominant plant taxa of the area include Astragalus mesites Buhse, Convolvulus arvensis L., Lolium persicum Boiss. & Hohen., Onobrychis cornuta (L.) Desv., Piptatherum holciforme (M. Bieb.) Roem. & Schult. var. holciforme, Prangos pabularia Lindl. and Stipa capillata L. Alongside these taxa, Astragalus microcephalus Willd. is the dominant element of the vegetation especially on uneroded slopes. The altitude of the new species ranges from 1750 – 1900 m.

Fig. 1.

Astragalus ihsancalisii – A: habit of fruiting plant; B: leaves and infructescences; C: part of leaf, adaxial surface; D: flowers, one truncated; E: stipe of legume. – Type locality, 26 June 2015, photographed by A. A. Dönmez.

Conservation status — The type locality of the new species is a semi-desert steppe with saline soil, vegetation cover is weak and water supply is low. Overgrazing has not been observed in the area, especially for the new species. The topography and soil structure in the area are not appropriate for various agricultural activities and there is no distinct threat to the new species. In 2018, the type locality was re-visited for further research on the population and to discover possible new subpopulations. Consequently, the new species remains known from a single locality with a small population composed of 20 – 25 observed individuals. The area of occupancy is estimated to be less than 1 km². According to IUCN (2012, 2017) criteria, the new species should be assigned to the category Critically Endangered: CR B1ab(iii,v)+2ab(iii,v).

Eponymy — Astragalus ihsancalisii is named in honour of the plant phytochemist, İhsan Çalış, retired from Hacettepe University. He is a well-known specialist on various major chemical components and has several publications on phytochemistry of Astragalus.

Discussion

Astragalus ihsancalisii is similar and possibly related to A. glaucophyllus, A. guzelsuensis and A. siahcheshmehensis. Hence, for a better insight into the identification of A. ihsancalisii, we compare all four species in Table 1.

Leaf surfaces show a similar structure based on SM and SEM observations (Fig. 2A – L). The adaxial surface is glabrous in Astragalus ihsancalisii (Fig. 1C; Fig. 2A, B), whereas it is sometimes sparsely hairy along the midvein in A. guzelsuensis according to the protologue (Ghahremaninejad & al. 2009), although our examination of the paratype of A. guzelsuensis (in GAZI) showed the adaxial leaflet surface to be glabrous (Fig. 2I, J). The abaxial surface of the leaflets in A. ihsancalisii and A. glaucophyllus is sparsely hairy (Fig. 2C, D, G, H), whereas in A. guzelsuensis it is glabrous (Fig. 2K, L). The trichomes of A. ihsancalisii and A. glaucophyllus are unicellular and densely papillose on the surface (Fig. 2C, G). All examined leaflets are amphistomatic, but the stomata are denser and larger on the adaxial surface (Fig. 2A, E, I). Stomata are also seen on the bract and legume surfaces. The stomata range from 15 – 20 µm in diameter and are of the Amaryllis type. Moreover, the stomata can also be considered as anomocytic and surrounded by polygonal epidermal cells (Fig. 2A – L). The leaflets seem to be glaucous under SM because of the thick epicuticular layer, which makes the plants adaptable to severe desertic conditions (Barthlott & al. 1997). Leaflets of all studied taxa exhibit a platelet wax type characteristic of Fabales (Barthlott & al. 1998). The variation observed for this character is insufficient to serve as a practical tool for taxonomic purposes in this group.

Table 1.

Comparison of Astragalus ihsancalisii with A. glaucophyllus, A. guzelsuensis and A. siahcheshmehensis.

The legumes of Astragalus ihsancalisii (Fig. 1E) and A. guzelsuensis are distinctly stipitate; this is according to our own observation of the paratype of A. guzelsuensis, although the protologue (Ghahremaninejad & al. 2009) described the legume as sessile. On the other hand, the legume of A. glaucophyllus is clearly sessile and can be used for definite discrimination of this species from the other three (Table 1).

Bract and legume micromorphology of the taxa (Fig. 2M – T) was compared to assess its taxonomic implications. The legume surface of Astragalus ihsancalisii and A. guzelsuensis is glabrous (Fig. 2M, N, Q, R, S), whereas that of A. glaucophyllus has white hairs and stomata (Fig. 2O, P). The legume surface in all species examined shares the same ornamentation composed of short parallel striae. Bracts are similar in terms of shape and papillate hairs at the apex (Fig. 2T), but bract length differs among the examined species (Table 1).

The calyx of Astragalus ihsancalisii has white and black hairs on both the tube and the teeth. In contrast, the calyx of A. guzelsuensis has a glabrous tube but has white and black hairs on the teeth.

Fig. 2.

Comparison of surface details of leaves, legumes and bracts by SEM. – Astragalus ihsancalisii (from A. A. Dönmez 19559): A, B: adaxial surface of leaf; C, D: abaxial surface of leaf; M, N: legume and detail of surface. – Astragalus glaucophyllus (from H. Sümbül 3639): E, F: adaxial surface of leaf; G, H: abaxial surface of leaf; O, P: legume and detail of surface; T: bract. – Astragalus guzelsuensis (from İ. Demir 496): I, J: adaxial surface of leaf; K, L: abaxial surface of leaf; Q, R, S: legume and detail of surface. – Scale bars: J = 10 µm; B, D, F, H, I, L = 20 µm; A, C, E, G, K, N, P, R, S = 100 µm; T = 0.5 mm; M, O, Q = 1 mm.

Additional specimens examined

Astragalus glaucophyllus Turkey: Amasya, in valle Kyrass-dere pr. Amasia, 400 m, 15 May 1890, J. Bornmüller 2802 ( P P03203374); Kirazdere, Logman Dapi etekleri, 800 m, 23 May 1990, H. Sümbül 3639 ( E E00341531, HUB); Sivas, Sivas-Zara road, 1300 m, 20 May 1960, Stainton 8452 ( E E00341530); “Tokat Anatoliae”, Wiedemann ( G G00020567); “Tokat” & “prope Tokat”, 21 Jul 1835, Wiedemann ( P P00605917). — Astragalus guzelsuensis Turkey: Van, Gürpınar, Güzelsu (Hoşap), between Zernek dam and Üçgen village, 2000 – 2200 m, 10 Jul 2007, İ Demir 496 (GAZI [paratype]); same locality, 2063 m, 12 May 2007, İ Demir 125 ( W 2008-07014 [isotype]). — Astragalus siahcheshmehensis Iran: Azarbayejan: Maku, Shote, Ghara Kelisa, NW slope, 39°05′29″N, 44°32′43″E, 1860 m, 7 Jun 2002, A. A. Maassoumi & S. R. Safavi 82564 ( B B10 0137935 [isotype],  MSB MSB-163532 [isotype]).