Oxalis filifoliolata J. Suda & Krejčíková, 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 : 18-20

Oxalis filifoliolata J. Suda & Krejčíková , sp. nov. ( Fig. 4 )

Species gracillima, multifoliolata. Pedunculi et item petioli tenues, basi articulati. Foliola saepissime 4-7, callosa . Petala coloris arancii, infra albo-marginata, basis viridi-flava, ostium coloris rubri lateris. Filamenta calva , edentata.

Type: — SOUTH AFRICA, Northern Cape Province, Namakwa District, Hantam Local Municipality: Gannabos north of Nieuwoudtville , 31°13’41.0’’S 19°15’33.9’’E, 420 m, 24 May 2011, J . Suda & J . Rauchová J11-155 (holotype NBG!, isotypes BOL!, PRC!, STEU!) .

Stemless, slender geophyte, 40–55 mm tall. Bulbs solitary, fusiform to narrowly ovate, 20–30 mm long, outer tunics dark brown, glabrous, inner tunics reddish-brown, papery. Rhizome 40–100 mm long, covered by glabrous, dark brown sheaths, with large, semi-amplexicaul scales at nodes in distal half, with 2–4 prominent apical scales surrounding bases of petioles and peduncles, apical scales apiculate, reddish-brown, glabrous. Leaves congested at apex of rhizome, 1–8 per plant, erect; petiole 35–50 mm long, with prominent basal articulation, white and slightly dilated below articulation, rigid, wiry, black, filiform above basal articulation, ± 0.4 mm in diameter; leaflets 4–7, peltately spreading, linear, conduplicate, glabrous, 7–15 mm × 1.0– 1.5 mm, apex emarginate with two distinct, round, orange calli. Peduncle 1-flowered, 40–55 mm long, filiform but slightly thicker than petioles, apically swollen, glabrous, black, shiny, basal articulation prominent, with portion below basal articulation slightly swollen and completely surrounded by scales; bracts 2, inserted on distal part of peduncle, alternate, filiform, black. Sepals triangular to lanceolate, 2.5–3.0 mm × 1.0– 1.5 mm, ecallose, acute, brown, streaked and blotched with dark brown markings abaxially, especially around margins. Flowers tristylous, corolla bright orange with brick-red to brownish throat and greenish-yellow, narrowly funnel-shaped tube, conspicuously whitish-edged on outer margin beneath. Petals adhering for ± 3–5 mm to form broadly funnel-shaped tube, oblanceolate, truncate to rounded, glabrous. Stamens 3-seriate with 2 series per plant, the shortest 2.0– 2.5 mm, the middle 3.5–4.0 mm, the longest 5.0–6.0 mm long and exserted ± 2 mm from tube; filaments pale yellow, glabrous, edentate; pollen yellow, tricolpate, tectum reticulate, with prominent blunt, scattered intra-luminary bacules. Ovary 1.2–1.4 mm long, ovoid, glabrous, 5-locular with 2– 3 ovules per locule; styles 5, glabrous, in three series with one series per plant, reciprocally herkogamous to stamen series, shortest ± 2.5 mm long, middle ± 3.5 mm long, longest ± 7.0 mm long; stigmas orange, fimbriate. Fruit not seen. Seeds not seen.

Diagnostic characters:— In its delicate habit, filiform petioles and linear leaflets, the new taxon superficially resembles the recently described O. ericifolia . However, peduncles of the new taxon lack the large swelling surrounding basal articulation that is characteristic of O. ericifolia , while the leaflets lack the large papillae on the adaxial leaflet epidermis. The very short petal claws of O. ericifolia result in open, campanulate flowers without a floral tube. This is very different to O. filifoliolata , which has much longer claws and a well-developed floral tube. The petal claws of O. ericifolia are red, with white petal lobes, while the claws of O. filifoliolata are greenish-yellow, the throat brick-red to brownish and the petal lobes bright orange. The filaments of O. ericifolia are wine-red, while those of O. filifoliolata are pale yellow ( Table 1). Oxalis filifoliolata also shows numerous morphological similarities to members of the highly variable O. flava clade ( Oberlander et al. 2011), and has the same type of pollen as all members of this clade ( Dreyer 1996). Similarities between O. filifoliolata and some of the multifoliolate forms of O. flava include the acaulescent to near acaulescent habit, glabrous leaves, distinct basal articulations on the petioles, with the petiole somewhat dilated below this articulation, and the multifoliolate leaves with a peltate leaflet arrangement. However, O. filifoliolata is substantially more delicate than any of the known forms of O. flava . It has dark brown outer bulb tunics, while the bulb tunics of O. flava are usually light brown. Each leaflet has two distinct orange apical calli, which are absent from the leaflets of O. flava . Oxalis flava usually has orange calli on its sepals, while the sepals of the new taxon are ecallose. Flower colours known from the O. flava complex include white, yellow and light pink, while the new taxon has orange flowers with a brick-red to brownish throat and greenish-yellow tube. The new taxon has glabrous, edentate filaments, while the filaments of O. flava are minutely glandular-pilose with obtuse teeth ( Table 1).

Oxalis pulvinata Salter (1940: 170) is another multifoliolate member of the O. flava clade ( Oberlander et al. 2011) with filiform petioles, which occurs in the same geographic region as O. filifoliolata and may be confused with it. Oxalis pulvinata differs from O. filifoliolata in having pale brown bulb tunics, pale rose or yellow petals and abruptly swollen, pulvinate lower and upper petiole articulations. Both its leaflets and sepals are ecallose, and the often blood red filaments bear distinct teeth.

Distribution and ecology: — Oxalis filifoliolata is known from a single population at Gannabos north of Nieuwoudtville en route to Loeriesfontein ( Fig. 2 ). The population is large, consisting of several thousand individuals spread over approximately two kilometres along the route. It is more abundant in the lower lying flat areas, but some individuals do occur on the slopes and even summits of the surrounding hills. The substrate is dry and very stony. Plants usually grow in open places unassociated with surrounding vegetation and are mostly exposed to full sun.

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

Phylogenetic analysis: —The ITS data set consisted of 41 taxa and 800 characters, of which 110 were parsimony-informative. Parsimony analyses of ITS found 353 trees of length 407 (CI: 0.568; RI: 0.657). Bayesian analyses provided 15 002 trees after burn-in (harmonic mean log likelihood: -3 566.6). All diagnostics indicated that both runs had converged on the same stable posterior distribution. Parsimony and Bayesian trees were very similar to each other and to trees in previous analyses using this marker ( Oberlander et al. 2009, 2011, Dreyer et al. 2010) ( Fig. 3 ). Although the O. flava clade is well-supported (PP: 1.00; BS: 81%), internal relationships are generally poorly resolved. The well-supported sister relationship between O. flava and O. monophylla Linnaeus (1771: 241) is complicated here by the new taxon, which resolves as sister to O. flava with only moderate support (PP: 0.84; BS: 68%). Although we also sequenced a non-coding plastid marker for the new taxon (the trn S- trn G spacer), more limited sampling for the O. flava clade compared to ITS precluded any conclusive findings beyond a well-supported relationship with two sequences of O. flava , although further relationships within this group were unresolved (data not shown).

Genome size: —The mean 2C-value was estimated to be 0.64 pg, showing the new species to be diploid. The monoploid genome size of O. filifoliolata is much smaller than the values determined for other members of the O. flava clade ( Fig. 5A ).

Conservation status: —The species is known from only one rather large population. Due to its restricted geographic area, O. filifoliolata deserves attention of conservation authorities. This plant would qualify as Vulnerable under South African Red List criteria ( Raimondo et al. 2009), due to a known range smaller than 20 km 2 and less than five known populations (Criterion D).

Etymology: —The specific epithet refers to the long, thin leaflets.

Note:— Non-flowering and partially dry material of O. filifoliolata was first observed in the Aloe dichotoma Masson (1776: 310) forest at Gannabos in September 2009, but was considered to be a multifoliolate form of the superficially similar O. ericifolia . Subsequent visits in May and June 2011, however, found the population in full flower, and the striking orange flowers clearly distinguished this species from O. ericifolia . It is very surprising that O. filifoliolata was only discovered now, given that it grows in sympatry with the charismatic and easily visible Aloe dichotoma . Oxalis filifoliolata produces bright orange flowers during May/June, which coincides with the flowering time of A. dichotoma , arguably a phenomenon that would attract many visitors to the site. The most plausible explanation for this late discovery of O. filifoliolata is its very diminutive size, and the inconspicuous leaves and leaflets. An unusual variety of O. flava var. unifoliolata Dreyer & Oberlander (2010: 258) was recently described from this same locality ( Dreyer et al. 2010).

Figures

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 4. Oxalis filifoliolata. a. illustration; b. flowering individual in its natural habitat; c. pollen.

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).