Ochna barbertonensis T.Shah, 2018

Shah, Toral, Burrows, John & Darbyshire, Iain, 2018, A new species of Ochna (Ochnaceae) from the Barberton Mountains of Mpumalanga, South Africa, Phytotaxa 374 (3), pp. 241-248 : 243-246

Ochna barbertonensis T.Shah sp. nov. ( Figs. 1 and 2 )

Diagnosis:— Ochna barbertonensis is most similar to Ochna confusa Burtt Davy with regards to its dwarf suffrutescent habit, narrowly elliptic leaf shape and serrulate leaf margin. However, it differs significantly in floral morphology: Ochna confusa has longitudinal anther dehiscence, an anther to filament ratio of 0.5:1 and a capitate stigma, whilst Ochna barbertonensis has poricidal anther dehiscence, anthers almost twice as long as the filaments and a style apex of 5 free, recurved lobes. In addition Ochna confusa has a large lignotuber with more robust erect branching, whilst Ochna barbertonensis has a thick horizontal woody rhizome with well-spaced, slender annual stems. (See Table 1.)

Type:— SOUTH AFRICA. Mpumalanga Province. Bearded Man, extreme eastern corner of Songimvelo Nature Reserve on border of Swaziland [eSwatini], above Satico Plantations , 1279 m, 26 September 2013, J. E. Burrows & S. M.Burrows 13729 (holotype: K!; isotypes: BNRH, LYD, PRE) .

Geoxylic suffrutex with thick horizontal rhizome, 2 cm thick, bearing multiple erect annual shoots up to ca. 20 cm tall. Branches grey, glabrous, lenticellate, sometimes peeling off in thin papery pieces, cylindrical; leafy branchlets brown, puberulent. Leaves lamina green when mature, reddish brown when young, glabrous, blade narrowly elliptic, 21–47 mm long, (6–)9–15(–18) mm wide, apex acute or sometimes obtuse, often with a conspicuous mucro extending up to 2.5 mm long, more so in young leaves, base attenuate to obtuse, margins serrulate with teeth incurving often ending in darkened mucronate tips, venation conspicuous, midrib raised abaxially and adaxially, lateral veins prominent extending to leaf margin, 10–14 pairs, tertiary veins reticulate, conspicuous; petioles up to 2 mm long. Stipules lateral to the petiole, sometimes nearly fused at base, semi-persistent, variable, linear to elongate-deltoid sometimes with broadened base, margins fringed, up to 5(–6.5) mm long. Inflorescences terminal, on leafless shoots from rhizomatous base, 2- to 9-flowered, condensed racemes, total inflorescence length 1.0– 3.5 cm, inflorescence axes puberulent, pale green, total length of pedicels (4–) 9–17 mm long at anthesis, length of pedicels below articulation point 2.5–6.0 mm, articulated mostly in proximal half; scales present on pedicels, translucent brown with darkened central line, linearensiform, navicular, caducous, 1.2–3.0 mm long; pedicels 12–18 mm long in immature fruit. Sepals 5, green, narrowly ovate to ovate, 5–7 mm long, 2–4 mm wide at anthesis; deep red, extending to 7–9 mm long in fruit, not reflexed (only immature fruits seen). Petals 5, bright yellow, obovate, clawed, concave when live, 6.0– 10.5 mm long, 3.5–6.0 mm wide, glabrous. Stamens many, more than 10, filaments 1–3 mm long, anthers 2–4 mm long, apically biporose. Carpels 5, styles gynobasic, united almost to the apex, 2.5–4.5 mm long, apices free with five spreading or recurved stigma lobes. Drupelets (immature) black, subglobose, attached at base, ca. 6 mm long, ca. 8 mm wide.

Distribution:— Ochna barbertonensis is confined to the Barberton Centre of Endemism ( Van Wyk & Smith 2001: 116), Mpumalanga, South Africa at an elevation of 1104–1320 m ( Fig. 3 ).

Habitat & Ecology:— The species grows on reddish clay-loams in short Barberton Montane Grassland ( Mucina & Rutherford 2006), which is usually burnt at least every second year. The geology is predominantly derived from shales, conglomerates, sandstones and siltstones of the Moodies Group of the Barberton Greenstone Belt ( Brandl et al. 2006). Associated geoxylic suffrutices growing with it are Parinari capensis Harvey (1862: 597) subsp. capensis and sometimes Elephantorrhiza elephantina ( Burchell 1824: 236) Skeels (1910: 29) .

Conservation Status:— Least Concern (LC). Ochna barbertonensis is only known from five collections within the Barberton Nature Reserve Phase 3 (Barberton Mountainlands Nature Reserve), the Songimvelo Nature Reserve and one collection from Shiyalongubo road where it is confined to a grassy verge between the road and a pine plantation. It has an estimated Extent of Occurrence (EOO) of 34 km 2 and Area of Occupancy (AOO) of 16 km 2, the latter using the standard 2 × 2 km grid cell recommended by the IUCN Standards and Petitions Subcommittee (2017). The Barberton Mountainlands Nature Reserve is a protected and well managed area, where the grasslands undergo rotational burning every three to four years and is irregularly grazed by herbivores. These conservation management practices favour this species and its associated habitat (D. Oosthuizen pers. comm.). The Songimvelo Nature Reserve forms part of the Lubombo Transfrontier Conservation Area established in June 2000, which is protected as a peace park between Swaziland and South Africa ( Smith et al. 2008). Therefore, although the geographic range of the species falls within the threatened categories ( IUCN 2012), the species is well protected and currently there are no immediate threats. However, due to its restricted distribution and its presence close to a road at one of its localities, it has the potential to fall into a threatened category if a threat arises in the future. It is therefore essential to continuously monitor this species. Furthermore, this species qualifies as ‘Rare’ under the Red List of South African Plants ( SANBI 2011) by having a restricted range of <500 km 2, whilst not being exposed to any direct or plausible potential threat and so not qualifying for a threatened category under the IUCN criteria.

Phenology:— Collected in flower between September and November. Collected with immature fruit in October. The Barberton Greenstone Belt has a summer rainfall pattern mainly from November to March, the flowering time of Ochna barbertonensis may correspond with early rains ( Changwe & Balkwill 2003, Williamson & Balkwill 2015).

Etymology:— The specific epithet refers to the Barberton Centre of Endemism to which the plant is restricted.

Additional specimens examined (Paratypes):— SOUTH AFRICA. Mpumalanga: Barberton Nature Reserve phase 3, Airstrip between Dycedale 368 JU and Wonderscheur 362 JU, 1104 m, 21 October 2017, Oosthuizen 2575 ( BMLH!) ; Shiyalongubo road embankment, straight section uphill and west of turnoff to remnants of Twello forestry station, Twello 373 JU, close to boundary of Zeist 363 junction, 1198 m, 1 November 2017, Oosthuizen & Froneman 2630 ( BMLH *) ; Barberton Mountainlands Private Nature Reserve , 1100 m, 28 October 2012, Turpin & von Staden 548 ( BNRH!) ; Barberton Mountainlands Private Nature Reserve, Shiyalongubo Gate on track leading W along fence, 1320 m, 10 November 2012, J. E. Burrows & S. M. Burrows 13080 ( BNRH!, J) .

Figures

FIGURE 1.—Ochna barbertonensis. A. Habit. B. Abaxial leaf surface. C. Detail of adaxial leaf margin. D. Detail of single serrulation showing mucronate tip. E. Two leaf apices: adaxial above, abaxial below. F. Three stipules. G. Open flower. H. Inner surface of sepal showing natural curvature. I. Inner surface of petal. J. Details of inner flower organs: gynobasic style, stigma lobes and anthers. K. Crosssection showing receptacle and ovules. L. Stamen. M. Scale. N. Immature fruits with persistent (not reflexed) sepals. O–P. Immature drupe. Q. Cross-section of single seeded fruit. Drawn by Andrew Brown from J.E.Burrows & S.M.Burrows 13729 (A–M) and Oosthuizen 2575 (N–Q).

FIGURE 2.—Photographs of Ochna barbertonensis in the field. A. Showing the grassland habitat. B. Showing suffrutescent habit. C. Flowers. D. Close of up of the flower showing poricidal anthers and style. Photos: John Burrows.

FIGURE 3.—Distribution map of Ochna barbertonensis in South Africa. Red circles represents the known species distribution based on herbarium specimens.