Allium elaounii El Mokni, 2022

Mokni, Ridha El, 2022, Allium elaounii: a new species of A. sect. Pseudoscorodon (Amaryllidaceae, Allioideae, Allieae) from Kroumirian mountains, Tunisia, Phytotaxa 533 (4), pp. 205-215 : 207-212

Allium elaounii El Mokni sp. nov. ( Figs. 1 , 2 , 3 )

Allium elaounii differs from closely related species with yellow/yellowish/yellowish-green/greenish-yellow perigone of the sect. Pseudoscorodon in the Mediterranean area by being a discreet small stemmed geophyte with typical bulbilliferous bulb in the sandstony Kroumirian-Tunisian oak forests mountains with leaves totally glabrous rather than hairy, face blades striated abaxially, inflorescences obviously hemispherical to fastigiate rather than densely and elliptical to fastigiate, ovary ovoid to pyriform rather than subglobose and trigonous, seeds granular to tuberculate with fine ridges and few folds rather than irregularly ovate-angular or semi-ovoid.

Type:— TUNISIA. Kroumirian-Jendouba Province: Béni Mtir Village , in the mixed oak forest, elevation 907 m, 19 May 2020, R . El Mokni 11190520 (holotype: Herbarium El Mokni at the Faculty of Pharmacy of Monastir! Isotypes : HFLA!, PAL!) .

Bulb ovoid-ellipsoid to ellipsoid, 12–18 × 10–12 mm, solitary, sometimes with 1–2 bulbils 5–6 × 3–4 mm; outer tunics fibrous, light brown to brownish, and inner ones membranaceous, whitish. Stem 21–26 cm tall, cylindrical, erect, striate, glabrous, pale yellow, covered by leaf sheaths up to 1/3–3/5 of total length. Leaves 4, green, glabrous; blade 10–13 cm long, 3.6–4.0 mm wide, linear, semi-cylindrical, fistulous, striated abaxially. Spathe persistent, with two unequal, opposite, erect valves, much shorter than the inflorescence, markedly beaked, the longer 4–6 nerved with 8.3–11.7(–18.7) mm long and 2.8–4.8(–6.2) mm large, the shorter 3 nerved with 5.8–11.1(–12.4) mm long and 1.8–3.6 mm large. Inflorescence hemispherical to fastigiate, lax, 16–25 × 14–19 mm, 11–16(–20)-flowered; pedicels unequal, 4–13(–14) mm long, erect to slightly curved at anthesis. Perigone campanulate, with tepals sub-equal, yellow with pale green, oblong to ovate, obtuse at apex, 4.8–6.6 mm long, 1.6–2.2 mm wide, with greenish-brownish midvein. Stamens exserted from the perigone, with filaments unequal, yellow-brownish, the outer ones 6.8–8.1 mm long, the inner ones 3.5–4.6 mm long, connate below into an annulus ca. 0.6–0.8 mm high; anthers yellow-brownish, oblong, 1.9 2.0 × 0.9–1.1 mm, rounded at apex. Ovary ovoid, smooth, greenish-yellow, 1.7–2.2 × 1.3–1.4 mm, papillose in the upper part with well-developed nectariferous pores ca. 1/3 to 3/5 high; style pale yellow, 1.2–3.1 mm long, extending up to 4 mm after fertilization. Capsule subglobose to pyriform, 4.2–4.6 × 4.1–4.3 mm, greenish with purplish-brown apical part. Seeds 3 × 1.5 mm, trigonous, granular to tuberculate with fine ridges and few folds, black.

Phenology:— Allium elaounii flowers in late spring-early summer from June to July; capsules are mature from the second half of July to August.

Etymology:—This species is named in honor of the eminent Tunisian Professor Mohamed Hédi El Aouni, who dedicated his life in teaching Plant diversity, Ecology and Taxonomy of the Tunisian Flora at the Faculty of Sciences of Bizerta (Carthage University), since 1981 and with whom I had my first lessons in Botany.

Common name (assigned here):—elaouni garlic (“ ’’: Tunisian name).

Distribution and ecology:—The distribution of Allium elaounii is restricted to Kroumirian-Jendouba Province, Béni Mtir region in the Northwestern of Tunisia, where it grows on loamy-sandy soils (deriving from clay sandstone series of the ‘ numidian flyshs ’) in wet meadows and scrubs of mixed oak ( Quercus suber L. and Q. canariensis Willd. ) forest between 860–920 m of elevation. Species associated with A. elaounii include mainly Aira tenorei Guss. , Aphanes arvensis L., Brachypodium distachyum (L.) P.Beauv., Calicotome villosa (Poir.) Link , Carthamus caeruleus L., Cistus monspeliensis L., C. salviifolius L., Convolvulus durandoi Pomel , Cytisus villosus Pourr. , Dactylis glomerata L., Erica arborea L., Erodium populifolium L’Hér. , Filago asterisciflora (Lam.) Sweet , Hypericum humifusum L., Hypochaeris glabra L., Luzula forsteri (Sm.) DC. , Medicago sp. pl., Quercus canariensis Willd. , Q. suber L., Stachys arvensis L., Veronica agrestis L., Lythrum junceum Banks & Sol. , Mentha pulegium L., Paronychia echinulata Chater , Plantago sp. pl., Prunella laciniata (L.) L., Sherardia arvensis L., and Trifolium sp. pl.

Conservation status:— Based on our observations, the type locality of A. elaounii is under over-grazing pressure and eventual man-made fires. The Area Of Occupancy (AOO) does not reach 8 km 2 and the Extent Of Occurrence (EOO) is less than 100 km 2 for both known sites. Hence, following the criteria established by IUCN ( IUCN 2021 ) and by the application of the criterion D (number of mature individuals ca. 27 ≤ 50), also according to the criterion C2 a(i) (only one subpopulation, and number of individuals ca. 13 ≤ 50 for each location), we here propose a provisional assessment of the Red List category for A. elaounii as a ‘ Critically Endangered’ species (CR, C2 a(i)+D).

Taxonomic notes:— Allium elaounii is morphologically closely related to A. rouyi group and A. valdecallosum . All five species share traits of reduced number of leaves (3–4), unequal and persistent spathe valves, absence of bulblets, lax umbel, campanulate perigone, yellow to yellowish tepals, simple stamens longer than perigone, almost ovoid ovary. However, some relevant morphological features differentiate A. elaounii from these two species, in its bulb outer coat, stem, leaves, inflorescence, pedicels, stamens, and seeds characters. The three species (where A. rouyi is considered in sensu lato) are compared in Table 1 and these traits are illustrated in Figs. 1–3 . In fact, detailed morphological investigations carried out on living plants allowed us to conclude that A. elaounii is a well differentiated species, clearly distinct from A. valdecallosum , which perigone shows typical basal callous thickening. Both share the tepal colour and the exserted stamens with A. flavum L. but have no strong affinities to this latter that has spathe valves much longer than the inflorescence. As highlighted in Table 1 , despite close affinities that A. elaounii shows with A. rouyi s.lat. and A. valdecallosum in sharing the same number (3–4) of leaves, campanulate perigone, obtuse tepals with greenish midvein, almost exerted stamens, yellow to yellow-brownish anthers, it differs by its short stem (21–26 cm) and small and typical bulbilliferous bulb with light-brown to brownish fibrous outer tunics. Moreover, in A. elaounii leaves are totally glabrous (including sheath and blade base) with a wider blade (3.6–4.0 mm) striated abaxially while A. valdecallosum diverges in having hairs on the sheaths and at the base of the blades with thinner blades (1.5–3.0 mm wide) when A. rouyi s.lat. shows very scattered leaf indumentum with generally thinner blades (0.5–1.0(–3.0) mm wide). In addition, inflorescence shows hemispherical to fastigiate shape with a low number of flowers (up to 20) opposing to ellipsoid to fastigiate, expanded or wide and hemispherical umbel with a high number of flowers (up to 58) in A. rouyi s.lat., a medium sized annulus (0.6–0.8 mm) compared to a much shorter (0.5 mm) and the longest (1.0 mm) in A. rouyi s.lat. and A. valdecallosum , respectively. Interestingly, stamens filaments are yellow-brownish colored in A. elaounii opposing to yellowish-purplish in A. rouyi s.lat. and only yellowish in A. valdecallosum . Besides, A. elaounii differs from A. valdecallosum in having ovoid to pyriform ovary rather than subglobose. One more relevant difference concerns seeds shape of A. elaounii , since preliminarily macromorphological photos show trigonous shape, granular to tuberculate aspect with fine ridges and few folds contrary to irregularly ovate-angular in A. rouyi s.lat. and semi-ovoid in A. valdecallosum .

From a chorological viewpoint ( Fig. 4 ), Allium elaounii shows a clearly distant distribution area from A. rouyi group, a southern Spanish endemic ( Stearn 1980, Pastor & Diosdado 1995, Aedo Pérez 2013) and A. valdecallosum Maire & Weiller , a calcareous chasmophyte endemic of the Moroccan High Atlas Mountains ( Rankou et al. 2013, Brullo et al. 2018). No data till now from Algeria about Allium subg. Allium sect. Pseudoscorodon with yellow/ yellowish perigone, albeit unpublished data were recent presented by Vela & Rebbas (2021).

According to Dobignard & Chatelain (2010), APD (2021), Euro+Med PlantBase (2006+) and Brullo et al. (2019), the number of Allium species belonging to A. sect. Pseudoscorodon sensu Brullo et al. (2019: 130) currently occurring in North Africa does not exceed 4. We here present a diagnostic key to these species together with Allium elaounii in which main distinguishing morphological features (referring essentially to leaves aspect and perigone/tepals color) are highlighted.

Figures

FIGURE 1. Allium elaounii sp. nov. (A) habit and habitat; pale yellow, erect stem (B) glabrous leaves including sheath and blade base, (C) umbel with closed spathe valves before blooming, (D–E) bulb with bulbils; whitish membranaceous inner tunics, light brown fibrous outer tunics. Phot. by R. El Mokni.

FIGURE 2. Allium elaounii sp. nov. (A–H) sequential stages of anthesis, 4–6 nerved longer spathe valve markedly beaked, campanulate perigone with sub-equal yellow with pale green tepals and greenish brownish midvein, exserted stamens, (J) full flowering umbel, (K) end of anthesis with persistent spathe valves, greenish subglobose capsule with purplish-brown apical part. Phot.by R. El Mokni.

FIGURE 3. Macromorphological shape of seeds of Allium elaounii. (A) and (B) dorsal face, (C) ventral face, (D) dorsal face.

FIGURE 4. Distribution map and main localities of Allium species with yellow/yellowish/yellowish-green/greenish-yellow perigone of A. sect. Pseudoscorodon in the Mediterranean area, still no published data available from Algeria (Wilaya of M’Sila).