Oxalis carolina J. Suda & Sudová, 2013

Suda, Jan, Krejčíková, Jana, Sudová, Radka, Oberlander, Kenneth C. & Dreyer, Léanne L., 2013, Two new species of Oxalis (Oxalidaceae) from the Greater Cape Floristic Region, Phytotaxa 124 (1), pp. 13-24 : 15-17

Oxalis carolina J. Suda & Sudová , sp. nov. ( Fig. 1 )

Species multifoliolata, O. tomentosae similis , sed robustior, petiolis longioribus, foliolis paucioribus (numero 9-11) sed maioribus. Corolla cum tuba calva . Sepala cum apicibus retrorsis.

Type: — SOUTH AFRICA, Northern Cape Province, Namakwa District, Hantam Local Municipality : southwest-facing slopes above the road R357 , 12.3 km north of Nieuwoudtville , 31°16’52.6’’S 19°08’37.2’’E, 550 m, 9 June 2010, J . Suda & R . Sudová J628 (holotype NBG!, isotypes PRC!, STEU!) .

Robust geophyte, stemless or rarely with shortly (<12 mm) exserted above-ground stem. Bulbs solitary, ovate with prominent beak, up to 25 mm long, outer tunics dark brown, glabrous, inner tunics reddish-brown; young bulbs lanceolate, much narrower (usually less than 5 mm broad) than mature bulbs, with paler tunics. Rhizome up to 30 cm long, often with numerous, prominently beaked bulbils. Leaves congested at apex of rhizome or above-ground stem, 3–12 per plant, erect, increasing in size after flowering; petiole 3–13 cm at flowering, elongating up to 25 cm later in the season, densely pilose with long (exceeding the diameter of the petiole), patent, stout, grey trichomes; leaflets (7–)9–11(–12), peltately spreading, oblong to narrowly obovate, 10–40 mm × 1–8 mm (larger in full shade), slightly conduplicate at flowering, but flat or weakly involute at fruiting stage, tomentose with grey, stout hairs, more densely so abaxially, mid-vein dilated and prominent beneath in proximal half of leaflet, apex emarginate, abaxial surface with scattered, round, orange calli that became larger and elongated towards apex. Peduncle 1-flowered, 3–14 cm long, usually only slightly longer than leaves, pilose with long grey hairs; bracts alternate, enclosing calyx, filiform to narrowly lanceolate, 2.0–3.0 mm × 0.2–0.3 mm, sparsely pilose. Sepals narrowly to broadly lanceolate, 4–6 mm × 1–2 mm, tips distinctly recurved, densely pilose abaxially (especially near base), glabrous adaxially, margins and sometimes surface brownish red, with two inconspicuous, orange calli near apex. Flowers tristylous, corolla white to pale lilac, with narrowly funnel-shaped, white to yellow, glabrous tube. Petals broadly obovate, 2.0– 3.5 cm × 0.8–1.2 cm, with distinct claw ± as long as or slightly shorter than lamina. Stamens 3-seriate with 2 series per plant, shortest series 2.5–3.5 mm, middle 4.0–5.0 mm, longest 8.0–10.0 mm long, filaments sparsely pilose, dilating towards base, with distinct, glabrous, papery teeth on the longer filaments, ± 2.5 × 0.2 mm; pollen tricolpate, tectum reticulate, with prominent blunt, scattered intra-luminary bacules. Ovary ovoid, densely pilose in distal half; styles 5, pilose, in three series with one series per plant, reciprocally herkogamous to stamen series, shortest ± 3 mm long, middle 5–6 mm, longest 8–10 mm long; stigmas yellow, fimbriate. Fruit not seen. Seeds not seen.

Diagnostic characters:— Oxalis carolina is morphologically most similar to O. tomentosa from the SW Cape. In addition to a clear geographic gap between the distributional ranges of these two species, O. carolina is a more robust plant, with longer petioles and fewer, but larger leaflets (mostly 9–11 compared to 10–20 in O. tomentosa ). Another distinct feature of O. carolina is the presence of recurved sepal tips ( Table 1, Fig. 1 ). In addition, O. tomentosa has a pubescent corolla tube, while the corolla tube of O. carolina is glabrous. Despite morphological similarities, O. carolina can hardly be regarded as a recent autopolyploid derivative of the diploid O. tomentosa , because their monoploid genome sizes differ by ca. 10% (1Cx-values for O. carolina and O. tomentosa are 0.29 pg and 0.32 pg, respectively). Nonetheless, detailed molecular work is required to accurately identify progenitors of the new species. Oxalis palmifrons T.M. Salter (1936: 161) and O. saltusbelli are two other multifoliolate species found in the Northern Cape Province. The former is easily recognized by very numerous leaves with more than 20 leaflets and markedly compressed petioles. The recently described O. saltusbelli from the Nieuwoudtville area has uniquely grooved petioles, its mature leaflets are narrower and indumentum is sparser and softer than that of O. carolina ( Table 1). Other potentially sympatric multifoliolate species (e.g., O. zeyheri Sonder in Harvey & Sonder (1860: 347)) are prominently caulescent and thus easy to distinguish from O. carolina .

Distribution and ecology: — Oxalis carolina grows on southwest-facing slopes above the road R357 north of Nieuwoudtville, in open Hantam Karoo vegetation ( Fig. 2 ). Other Oxalis species recorded at this locality include O. callosa R. Knuth (1927: 15) , O. flava , O. obtusa and O. suteroides T.M. Salter (1935: 116) . The slope is very stony and the long rhizome of O. carolina appears to be an adaptation to these conditions. Bulbs are deeply-seated in loamy soil and were often found below boulders or in crevices between stones. A regular sympatric occurrence of mosses indicates enough moisture during the growth season. Oxalis carolina generally favours shaded microsites, sheltered either by boulders or by surrounding shrubby vegetation, and the species is exposed to direct sunlight only occasionally and for short periods. The size of the population was estimated at a few hundred individuals. Plants often grow aggregated into clumps. Only a small proportion of individuals were flowering (and flowers were seldom fully open), while most plants produced only leaves. The palmately compound leaves superficially resemble some multifoliolate Lupinus (Fabaceae) species. Vegetative reproduction via bulbils seems to be the prevailing mode of propagation; bulbils are especially common along the rhizome in autumn. Although it is possible that other populations of O. carolina occur in the area, our repeated searches during 2011–2012 in localities with similar ecological conditions were not successful.

Phenology: —The species flowers from mid-May to late June.

Phylogenetic analysis: —The ITS data set consisted of 20 taxa and 783 characters, of which 58 were parsimony-informative. The trn L- trn L- trn F data set consisted of 20 taxa and 937 characters, of which 16 were parsimony-informative. Parsimony analyses of ITS and trn L- trn L- trn F found 15 trees of length 221 (CI: 0.760; RI: 0.694), and 78 600 trees of length 81 (CI: 0.951; RI: 0.909), respectively. Bayesian analyses provided 15 002 trees after burn-in (harmonic mean log likelihood ITS: -2 437.37, trn L- trn L- trn F: -1 854.72). All diagnostics indicated that all runs for each marker had converged on the same stable posterior distributions. Parsimony and Bayesian trees were very similar, and similar to previous analyses using these markers ( Oberlander et al. 2009, 2011, Dreyer et al. 2010). The O. tomentosa alliance is strongly supported as a monophyletic group in the ITS data set ( Fig. 3 ), with O. carolina and two accessions of O. palmifrons resolving with the multifoliolate members of the alliance (PP: 1.00; BS: 98%). In contrast, O. palmifrons does not group with the remainder of the alliance in trn L- trn L- trn F trees, and O. carolina is only weakly supported (PP: 0.98; BS: 53%) as sister to the remaining species of the alliance. The ILD test in PAUP* showed that the ITS and trn L- trn L- trn F data sets were barely congruent with one another (P = 0.067). Although clearly associated with members of the O. tomentosa alliance in both analyses, neither nuclear nor plastid data support a close relationship of O. carolina to any particular member species.

Genome size: —The mean 2C-value was estimated to be 1.16 pg, showing the new species to be tetraploid. The amount of nuclear DNA is very different from the closest relatives of O. carolina (i.e., O. oligophylla T.M. Salter (1938: 114) , O. palmifrons , O. saltusbelli and O. tomentosa ), all of which are uniformly diploid according to flow cytometric analysis ( Fig. 5B ); another related species, O. hygrophila Dreyer (2004: 262) , seems to be hexaploid on the basis of genome size data.

Conservation status: —The species is known from only one very localized population consisting of a few hundred individuals. Because the population occurs close to the road verge, it may be threatened by possible future road construction. This species would qualify as Vulnerable under South African Red List Criteria ( Raimondo et al. 2009), due to a geographic range of less than 20 km 2 and only one known population (Criterion D).

Etymology: —The specific epithet honours the Charles University in Prague (Universitas Carolina Pragensis), which is the oldest university in Central Europe and Alma Mater of the first three authors.

Figures

FIGURE 1. Oxalis carolina. a. flowering individual in spring; b. bulb; c. sterile plant in autumn; d. pollen.

FIGURE 2. Geographic distribution of Oxalis carolina (circle) and O. filifoliolata (diamond).

FIGURE 3. Phylogenetic placement of a) Oxalis carolina based on ITS and trnL-trnL-trnF sequence data; and b) O. filifoliolata based on ITS sequence data. All trees presented are Bayesian 50% majority-rule consensus trees. Numbers below the branches indicate Bayesian Posterior Probability values, numbers above the branches refer to Parsimony Bootstrap values. The new taxa are highlighted in larger, bold font. The shading in a) indicates the O. tomentosa alliance.

FIGURE 5. Fluorescence histograms showing simultaneous analysis of a) O. filifoliolata and its closest relative O. flava (differing ~20% in their genome sizes); and b) O. carolina and morphologically most similar O. tomentosa (differing ~80% in their genome sizes).