Oxalis nivea Roets, Dreyer & Oberl., 2013

Dreyer, Léanne L., Roets, Francois & Oberlander, Kenneth C., 2013, Two new Oxalis (Oxalidaceae) species from the Richtersveld National Park, South Africa, Phytotaxa 89 (2), pp. 53-63 : 57-58

Oxalis nivea Roets, Dreyer & Oberl. , spec. nov. ( Figure 1 )

Oxalis nivea is characterized by having multi-flowered inflorescences with white flowers, carried on very long peduncles. It has dark brown to blackish bulbs, with hard sclerenchymatous tunics that are irregularly ridged due to large internal channels.

Type:— SOUTH AFRICA. Northern Cape Province: Richtersveld National Park , ca. 1 km from R14 turn-off to Kokerboomkloof, 28°17.692S, 17°02.214E, 420 m, 11 July 2011, Roets, Dreyer & Oberlander 2011 /07-11 (holotype STEU!, isotypes NBG!, BOL!) .

Geophyte, up to 400 mm tall. Bulb ovate to ovoid, with a contractile root, clear apical beak present, beak a third to half of total length, 25–35 × 20 mm, tunics irregularly longitudinally ridged due to large internal channels, sclerenchymatous, dark brown to blackish, glabrous, surface finely reticulate. Rhizome vertical, up to 70 mm long, thickening conspicuously at ground level, sparsely glandular-hairy, adventitious roots arising along entire length, upper rhizome nodes with pale, glabrous, semi-amplexicaul scales; sheath absent. Aboveground stem present, 20–100 mm long, semi-succulent, glabrous, nodes with 1–2 scales or cauline leaves. Leaves 10–20 per plant, apically congested, trifoliolate, bright green; petioles 20–60 mm long, with prominent basal articulations, sparsely covered with simple hairs; leaflets distinctly petiolulate, obcordate, 7–13 × 8–18 mm, adaxially sparsely hairy along main veins, abaxially sparsely hairy, becoming more hairy towards base, margin sparsely hairy. Peduncles 1–4 per plant, each with 6–11 terminal flowers, at least three times as long as petioles, up to 250 mm long, twice as thick as petioles, semi-succulent, glabrous; bracts many, 4–6 mm long, distinctly callose on upper margins for up to half of bract length, sparsely hairy abaxially, linear to linear-lanceolate, with acute tip. Pedicels slender, sparsely hairy, 8–20 mm long when mature. Sepals of unequal length, 4–9 × 1–2 mm, linear-lanceolate, apex acute, mostly with two small, distinct orange calli, sparsely hairy. Corolla 17–20 mm long, white with funnel-shaped light yellow tube, tube about half the length of corolla, petals oblanceolate, apex truncate with margin finely irregular, glabrous, ecallose. Stamens in 3 series, 2 series per plant, the shortest level 3–4 mm, the middle level 3.5–4 mm and the longest level 7.5–8 mm long, basally connate; anthers oblong, yellow to orange; filaments pale, with simple hairs along entire length; filament teeth 1.8–2 mm long from base, apically acute. Ovary 2 mm long, narrowly ovoid, densely hairy on upper half, with few scattered hairs on lower half, 5-locular with 20–22 ovules per locule; styles 5, separate, in three series with one series per plant, shortest level 3.5 mm long, middle level 4.0 mm long, longest level 7.5 mm long, erect, densely hairy; stigmas green, fimbriate. Fruit an elongate capsule extending well beyond the sepals, up to 15.0 mm long. Seeds with endosperm.

Distribution:— Oxalis nivea is known from the type locality only. The species was discovered growing on south-facing slopes near the base and at the summit of the Koeroegab Pass in the Richtersveld National Park. It grows in full sun on these cooler slopes, in very rocky soil. Oxalis nivea was in full flower in mid- July. All three stylar morphs were observed in this population.

Notes:— The specific epithet of O. nivea refers to its pure white petal laminas, which clearly distinguish it from O. pes-caprae , the species to which it bears the strongest resemblance.

Figures

FIGURE 1. Bayesian analyses 50% majority-rule consensus trees. Parsimony bootstrap support values> 70 % are shown above branches, Bayesian posterior probability values> 0.95 are shown below the branches. The O. pes-caprae clade is indicated. The two new species are indicated in bold. Bars below trees indicate expected number of substitutions per site. A) tree based on ITS data. B) tree based on trnSG data.