Wadithamnus gabrielii Baldesi

Baldesi, Giacomo, 2024, A new species of the genus Wadithamnus (Amaranthaceae, Achyranthoid) from north-eastern Somalia, Phytotaxa 641 (2), pp. 170-176 : 171-174

Wadithamnus gabrielii Baldesi , sp. nov. ( Figs. 1–3 ).

Types: — SOMALIA: Bari region, Escushuban (Iskushuban), gebirgsrand NE von Escuschuban (foothills/edge of the mountain range NE of Iskushuban ), ‘schiefe Ebene’ (sloping plateau), 800 m, 19 March 1989, Gabriel s.n. (holotypus: FT barcode FT0010042 !, isotypus: B barcode B10 1161441 !) .

Diagnosis: — Ab Wadithamnus artemisioides (Vierh. & O.Schwartz) T.Hammer & R.W.Davis foliis angustioris (1–2 mm latis vs. 2–12 mm) inflorescentiisque brevissimis distinguitur.

Description: —Shrub, 30 – 40 cm high. Stems terete, densely tomentose with white dendritic hairs (sometimes contracted and appearing stellate). Leaves flat, greyish-green, linear-oblong or narrowly oblanceolate, blade thick (almost sub-succulent). c. 7 – 15 × 1 – 2 mm, with a dense indumentum of short dendritic hairs; base attenuate, sessile or shortly petiolate (petiole up to 2 mm); apex rounded; midrib obscure adaxially and raised abaxially; margins thickened and sometimes appearing revolute. Synflorescence terminal and contracted, with 3-flowered cymules; each cymule 1 – 3 mm long and c. 2 mm wide, the lower ones subtended by a more or less leafy bract; inflorescence branches, bracts, bracteoles and flowers covered with a dense indumentum of whitish dendritic hairs; bracts and bracteoles similar in size and shape, c. 0.5 – 1.0 × 0.5 mm. Flowers subsessile; sepals 6; outer sepals 2, elliptic to ovate c. 1 – 1.3 × 0.6 mm, adaxially glabrous, broadly membranous at margins; inner sepals 4, narrowly elliptic, c. 1 x 0.4 mm, adaxially glabrous, membranous at margins. Staminal cup symmetrical, c. 0.3 mm long; staminal cup appendages present, triangular. Stamens 4; filaments glabrous, c. 0.3 mm long; anthers c. 0.3 mm long. Ovary globose, glabrous, c. 0.4 × 0.4 mm; stigma sessile, capitate. Capsule and seed not seen.

Etymology: —This species is dedicated to Prof. Dr. Baldur Gabriel, hydrogeologist in Berlin. During three field trips to NE-Somalia in the late 1980s he collected around 650 specimens deposited at Berlin herbarium including the only known specimens of the new species.

Distribution and ecology:—The genus Wadithamnus was previously considered endemic to the Arabian Peninsula ( Yemen and Oman), this new taxon broadens the distribution of this genus to include NE-Somalia. Wadithamnus gabrielii is known so far only from the type collection and its distribution is unknown at present. The label of the specimen reports it is growing on a slope in the Dharoor valley NE of Iskushuban. The precise locality is not specified but, according to the label, a mountain ridge is present in proximity to the plain north of Iskushuban (more NW actually), no toponyms are reported for this area so it is likely that geomorphological features were used as a reference point instead. The geologic substrate in the area is sedimentary, the Dharoor valley is covered by sands, silts and gravels of recent deposition over the Iskushuban formation, constituded of lagoonal marls, calys, sandstones, gypsum, limestone and fine conglomerates ( Abbate et al. 1994). While the mountains north of the valley are ascribable to the Auradu limestones (shelf limestones with intercalation of marls and cherts), the Taleh evaporites (anydrithes, gyspum, dolomites, limestones and shales) and in part to the Karkaar limestones (limestones and marl intercalations), the mountain edge (likely where the specimens were collected) is constituted of alluvial fanglomerates (boulder beds) and coarse sandstone ( Abbate et al. 1994). The local climate is classified as very arid; semidesert grassland and shrubland dominate the landscape together with the true desert, which occupies a good portion of the Bari region (Ullah & Gadain 2016).

Notes: — Wadithamnus gabrielii differs from W. artemisioides by its smaller and narrower leaves and the shortened synflorescence. This new species shares similarities with both subspecies of W. atremisioides : the shortly petiolate leaves with a thick blade are similar to those of subsp. batharitica from Oman but the latter has much wider leaves (5–12 mm) compared to W. gabrielii (1–2 mm), while the linear to oblanceolate leaves with an attenuate base are reminiscent of those of subsp. artemisioides , which has long (10–40 mm vs. 7–15 mm) and narrow leaves (2–5 mm vs. 1–2 mm) with a long-attenuate base into petiole and a thin blade. The synflorescence of W. gabrielii is rather characteristc being much shorter and almost contracted in comparison to W. artemisioides subspp., which have long, slender and elongated synflorenscences (up to 7–9 cm) counting many cymules while the former has compact and much shorter synflorescences (up to 2.5 cm) with few cymules instead. Pollen morphology of W. gabrielii was observed under standard light microscopy without any pretreatment; shape and dimension of the pollen grains are practicaly identical to those of W. artemisioides subsp. batharitica as reported and illustrated in Bellini et al. (2022; see supplementary material S 1 p. 3 and p. 13 Fig. S2 a–b ).

Conservation status: —The occurrence of this taxon might be relatively circumscribed and a considerable period of time has elapsed since its last (first and only in this case as it is known from only one gathering in 1989 from an imprecise locality) record. In absence of data about its distribution, conservation status of its habitat and considering no up-to-date information on the nature and extent of threats is available (Ullah & Gadain 2016), this species has to be preliminarily assessed as Data Deficient (DD) ( IUCN 2022).

Figures

FIGURE 1. Scan of the isotype of Wadithamnus gabrielii (B10 1161441).

FIGURE 2. Flower anatomy of Wadithamnus gabrielii: a flower bud with the two cymule bracts; b close up of rehydated flower under water (outer tepals and one inner tepal removed); c flower close up (outer tepals and one inner tepal removed); d flower parts abaxial view, from left: two cymule bracts, two outer tepals, one inner tepal and dissected flower (see c); e adaxial view of outer bracts and two inner bracts; f close up of flower showing the globose and sessile stigma (outer tepals, two inner tepals and anthers removed); g anthers close up; h flower bud close up showing the indumentum. (scale bar 0,5 mm if not indicated).

FIGURE 3. Synflorescence close up. Scale bar 1mm.