Bituminaria bituminosa(L.) C.H. Stirt. affinis, sed habitu suffruticoso, ramis lignosis, foliolis glabris vel sparsim pilosis, subrotundatis vel ovatis, max. 35 mm longis, petiolis usque ad 6 cm longis, inflorescentia laxa, saepe subspicata, 1,5-2 cm longa, 3-10-flora, calice 12-13.5 mm longo, corolla pallida.

Figure 1. 

Diagnostic features regarding the reproductive structures of Bituminaria antiatlantica. A Flower (ventral view) B Flower (dorsal view) C Flower (lateral view) D Bud E Standard F Wings G Keel (lateral view) H Calyx (open) I Staminal tube J Anthers K Pisti L Stigma M Fruiting calyx and pod N Pods O Seed. Illustration by S. Brullo based on living material coming from Mount Tachilla and Djebel Imzi in Morocco (CAT).

Figure 2. 

Diagnostic features regarding the vegetative structures of Bituminaria antiatlantica. A Habit B Leaves C Leaf apex (abaxial side) D Leaf apex (adaxial side) E Stipules. Illustration by S. Brullo based on living material coming from Mount Tachilla and Djebel Imzi in Morocco (CAT).

Psoralea bituminosa L. var. rotundata Maire, Bull. Soc. Hist. Nat. Afr. N. 27(8): 222, 1936.

Morocco: In rupibus arenaceis Mountis Tachilla ad radices septentr. Anti-Atlantis, 400 m, 10 April 1935, R. Maire & E. Wilczek s.n. (holotype MPU!; isotype RAB!), sub Psoralea bituminosa L. var. latifolia Moris f. rotundata).

Perennial, suffruticose, dark green, erect to ascending, up to 60 cm tall. Stems dark green-brown, sparsely hairy, with hairs short and appressed, very branched; branches woody, leafy along entire length. Stipules 5–6 mm long, rigid, linear-triangular, adnate to the petiole. Leaves pinnately 3-foliolate, green, with petiole 1.8–6(7) cm long, sparsely hairy; leaflets semi-round to ovate, subglabrous above and sparsely hairy below, 10–35 × 8–21 mm, with apex obtuse to acute, ending in a straight mucro 0.3–0.5 mm long. Inflorescence definite, subspicate, lax, 1.5–2 cm long, with 3–10 flowers. Peduncle 3.5–14 cm long, overtopping the leaves. Bracts 1–3 toothed, 5–8 mm long, subtending 2 or more flowers. Flowers 16–17 mm long. Calyx 12–13.5 mm long, green, densely hairy, with hairs white mixed to short black hairs; lower teeth 7–8 mm long, laterals shorter, 5.5–7 mm long. Corolla whitish-pink to whitish lilac; standard 16–16.5 × 7–7.5 mm, elliptic, striate with lilac in the middle, apex obtuse; wings 14–15 × 3–4 mm; keel 10.5–11 × 2–2.3 mm, having a macula dark violet in the upper part. Staminal tube 11–11.5 mm long, with anthers yellow, 0.7–0.8 × 0.3–0.35 mm; vexillary w with filament fused below with the other ones. Pistil 10–10.5 long, ovary hairy, style curved towards the apex, thickened at point of flexure, stigma capitate, penicillate. and ovary hairy. Pod 11–23 mm long (beak included), with beak pubescent, 14–16 mm long. Seed reniform, 6–7 × 3.4–4 mm.

Bituminaria antiatlantica is a rare and localized species, currently known only from Mount Tachilla and Djebel Imzi in the Anti-Atlas Mountains in southern Morocco, (Fig. 3). It grows between 300 and 1500 m of altitude, on steep, north-facing slopes, chiefly constituted of Precambrian quartzite. From the bioclimatic viewpoint, this area falls within the infra- and the thermo-mediterranean type, with semiarid to subhumid ombrotype (Benabid and Cuzin, 1997). This species is an element of a chasmophytic vegetation type characterized by Celsia longirostris Murb. var. antiatlantica Emb., Salvia taraxacifolia Coss. & Balansa, Chiladenus hesperius (Maire & Wilczek) Brullo, Teucrium werneri Emb., Aeonium arboreum (L.) Webb & Berthel, Dianthus lusitanus Brot., Micromeria hochreutineri (Briq.) Maire, Caralluma hesperidum Maire, Teline segonnei (Maire) Raynaud, Davallia canariensis (L.) Sm., Asplenium aethiopicum (Burm. fil.) Becherer (Fig. 4C). Besides, several phanaerophytes occur in these rupestrian habitats such as Dracaena draco L. subsp. ajgal Benabid & Cuzin, Laurus azorica (Seub.) Franco, Argania spinosa L., Kleinia anteuphorbium (L.) Haw., Rhus tripartita (Ucria) Grande, Euphorbia echinus Hook.f. & Coss., Warionia saharae Benth. et Coss. Many of these species are rare and endemic to the southern part of Morocco, thus highlighting the relic character of this plant community. In particular, Benabid and Cuzin (1997) consider B. antiatlantica (sub Psoralea bituminosa var. rotundata) as characteristic of a very peculiar and remarkable association exclusively occurring in a small area of the Anti Atlas range.

Figure 3. 

Distribution map of Bituminaria antiatlantica (red dots) based on herbarium specimens.

Figure 4. 

Phenological features of Bituminaria antiatlantica A Natural habitat with Bituminaria antiatlantica in Djebel Imzi (Morocco) B Habit of B. antiatlantica in Mount Tachilla (Morocco) C Natural habitat of B. antiatlantica with Dracaena draco L. subsp. ajgal in Djebel Imzi (Morocco) D Inflorescence detail of B. antiatlantica E Fructified inflorescence of B. antiatlantica F Leaf detail of B. antiatlantica (Photos by S. Cambria).

The specific epithet refers to the Anti-Atlas range, where the species occurs.

Based on current knowledge, Bituminaria antiatlantica seems to have a scattered distribution over an area smaller than 2,000 km2. Therefore, following the IUCN criteria (2014), this species should be classified as “Vulnerable” (VU B2). As regards the conservation policy of the growing site, it has been proposed its inclusion in the list of the UNESCO World Heritage Sites for its richness in endemic, rare or important plants, as well as for its breath-taking landscape (see http://whc.unesco.org/en/tentativelists/1180/).

As emphasized by several authors (Barthlott 1981, Koul et al. 2000, Kirkbride et al. 2003, Celep et al. 2012, Gandhi et al. 2011Brullo et al. 2011, 2013) seed coat micro-morphology plays an important role in the taxonomic survey at generic and specific level, especially in those rather critical groups. The seed testa sculptures of Bituminaria were investigated by Minissale et al. (2013), Giusso et al. (2015), Brullo et al. (2016) and Bogdanović et al. (2016), who highlighted the systematic relevance of these features providing additional information in order to discriminate among the allied species. In particular, the species hitherto examined are B. bituminosa, B. palaestina, B. kyreniae, B. basaltica and B. plumosa, which are characterized by different patterns of seed testa. In this study SEM investigations were carried out on the seed of B. antiatlantica, according to the protocol of Stork et al. (1980) using the terminology followed Bartholot (1981) and Gontcharova et al. (2009). The results revealed that seed coat sculptures of B. antiatlantica differ markedly from the species mentioned above. The seed testa of B. antiatlantica is characterized by a fine and inconspicuous reticulum, bordering the cells, which appears irregularly polygonal and 3.5–9(10) µm wide. The anticlinal walls are irregularly curved to straight, slightly grooved and smooth, while the periclinal walls are flat with the epidermis smooth to finely rugose (Fig. 5B–C). The pod corpus is characterized by minutely rugose surfaces, and the indumentum hairs are minutely papillose, with the longitudinal furrow broadly widened at the base (Fig. 5E–F).

Figure 5. 

SEM micrographs of seed testa (A–C) and pod hairs (D–F) of Bituminaria antiatlantica from Mount Tachilla in Morocco. A Seed at low magnification (× 15) B Seed testa at medium magnification (× 1000) C Seed testa at high magnification (× 2500) D Pods at low magnification (× 10) E Pod hairs at medium magnification (× 250) F Pod hairs at high magnification (× 700).

Previous studies of pollen morphology of Bituminaria included those by La Serna Ramos and Gó Mez Ferreras (2006) and Halbritter and Weis (2015), who published a SEM picture of B. bituminosa s.l., while Brullo et al. (2016) examined the pollen grains of B. bituminosa s.str. and B. palaestina, pointing out distinctive morphological differences between the pollen of the two species. In this study pollen grains of B. antiatlantica were excised from flower buds in ahydrated state and were examined according to Walker and Doyle (1975), Punt et al. (1994, 2007) and Hesse et al. (2009). The pollen grains are very similar to that of B. bituminosa sensu stricto from Sicily, which has been examined in detail by Brullo et al. (2016), although there are differences in size and ornamentations which distinguishes clearly the pollens of the two species. Actually, The pollen grain of B. bituminosa (Brullo et al., 2016, Fig. 6A) is smaller with a size of 25–30(34) µm, with larger brochi (4–17 µm) and fewer in number, showing a laxly papillose lumen and less deep (0.5–1 µm) and narrower (1–1.2 µm) muri. In B. antiatltantica, the pollen grain (Fig. 6) is slightly larger (37–38 µm) with smaller brochi (4.3–11 µm) and more numerous, with a lumen minutely papillose and muri deeper (1.4–1.8 µm) and larger (1.4–1.7 µm).

Figure 6. 

SEM micrographs of pollen grains of Bituminaria antiatlantica from Mount Tachilla. A–B Polar view (× 1600) C Equatorial view (× 1600) D Detail of pollen surfaces (× 4000).

Bituminaria antiatlantica shares some ecological and morphological characteristics with B. flaccida, a very rare species occurring in the semidesert countries of Jordan and Sinai in the Middle East; e.g., reduced leaflets, the size and few-flowered inflorescences, and flower colour. However, the latter differs from B. antiatlantica in several significant features (Table 1), such as its herbaceous habit, greyish-glaucous stems and leaves, obovate to linear-lanceolate and densely pubescent cauline leaflets, shorter calyx, longer and slightly retuse standard, shorter staminal tube, and feature of pod and seed.

Other specimens examined (paratypes). Morocco: Sulle rupi di quarzite arenacea del Jebel Tachilla a circa 200 m di altitudine, 16 June 2015, S. Cambria (CAT!); Sulle rupi di quarzite arenacea in una gola di Jebel Imzi, 300–400 m di altitudine, 19 June 2015, S. Cambria (CAT!); Sulle rupi di quarzite arenacea del Jebel Imzi a 1450 m di altitudine, 18 June 2015, S. Cambria (CAT!).