Barleria lebomboensis I.Darbysh., McCleland & Froneman, 2017

Darbyshire, Iain & Froneman, Willem, 2017, Barleria lebomboensis (Acanthaceae), an endangered new species from the Lebombo Mountains of Swaziland, Phytotaxa 323 (2), pp. 173-181 : 174-178

Barleria lebomboensis I.Darbysh., McCleland & Froneman sp. nov. ( Fig. 1 , 2 )

Type: — SWAZILAND. Lubombo District, Mhlumeni , 530 m, 6 June 2016, McCleland 1049 (holotype BNRH!; isotypes BNRH!, K!, SDNH!) .

Diagnosis:— Differs from Barleria meyeriana in the leaves being broadly ovate, length:width ratio 1.15 − 1.75(− 2) (versus in B. meyeriana leaves lanceolate or more rarely ovate, length:width ratio (1.5 −)2 − 4(− 6)), with base shallowly cordate or truncate (versus cuneate to rounded) and the lower surface conspicuously pubescent on the main veins and margin (versus lower surface with hairs restricted to margin and midrib); the inflorescence being a contracted spike (versus a lax spike with at least the lower flowers widely spaced); the corolla being markedly smaller, 21.0 − 25.5 mm (versus 35 − 48 mm) long; the limb and throat without darker markings (versus corolla with a conspicuous darker line running from the centre of the proximal portion of each lobe into the throat); and the capsule puberulent throughout (versus glabrous or puberulent only on the beak) and shorter, c. 11 mm (versus 14 − 17 mm long).

Differs from Barleria dolomiticola in the corolla limb being subregular, the abaxial lobe barely offset from the other four lobes (versus in B. dolomiticola corolla in marked 4+1 configuration, the abaxial lobe offset by 6 − 7 mm from the other four lobes); the corolla being smaller, 21.0 − 25.5 mm long (versus 30 − 50 mm), with the limb and throat without darker markings (versus corolla with conspicuous darker lines running from both the centre of the proximal portion of each lobe and the sinuses between the lobes into the throat); and the long eglandular stem and leaf hairs being ascending or sub-spreading and simple (versus hairs stiffly appressed and biramous).

Perennial herb with numerous trailing or procumbent stems from a woody base and rootstock, stems to 200–250 mm long, distal portion sometimes decumbent. Stems red-brown, later turning greenish, subangular, with numerous pale ascending to sub-spreading bristly hairs 0.7–1.1 mm long throughout, these sometimes with a bulbous base, and with short finer spreading hairs mostly on two opposite sides, distal-most internodes also with patent glandular hairs. Leaves sessile; or with petiole 3 mm long, broad and winged, with bristly hairs beneath; blade bluish-green often with purplish margin and veins beneath or suffused purple throughout abaxially, broadly ovate, 17–30 × 11.5– 23.0 mm (length:width ratio 1.15–1.75(–2):1), base shallowly cordate or truncate, apex acute or obtuse, minutely apiculate, adaxial surface glabrous, margin and main veins beneath with pale ascending hairs, often with a bulbous base, sometimes also with few short patent glandular hairs along margin of proximal half; lateral veins 3–5 pairs, ascending; cystoliths conspicuous on adaxial surface in dried material. Inflorescence a contracted terminal spike 20– 30 mm long, comprising a series of single-flowered opposite cymes; bracts foliaceous, but reducing upwards and becoming more elliptic or obovate, typically 11.5–15.5 × 4–7 mm, bracts of distal flowers can be oblanceolate and only 2.5 mm wide, indumentum as that of leaves, but glandular hairs often more numerous and can also be on the abaxial surface; bracteoles spathulate or linear-spathulate, 9.0–13.2 × 0.8–2.0 mm, apex acute or obtuse, often purple tinged towards apex and/or along margin, midrib prominent, strigulose, surface glandular-pubescent at least along margin. Calyx green in proximal portion, purple distally and along margin; anterior lobe oblong-lanceolate, 11–13 × 2.7–3.3 mm, widest at base, apex acute or usually notched for up to 1 mm, external surface with 4 or 6 prominent parallel veins, patent glandular pubescent and veins also ascending-strigose; posterior lobe as anterior lobe, but 11.7–13.7 mm long, marginally narrower, apex acute, surface with (3 or) 5 prominent veins; lateral lobes linear-lanceolate, 6.5–10.0 × 1.0– 1.3 mm, glandular-pubescent in distal half. Corolla pale blue or lilac with a white tube, lobes with marginally darker midvein, 21.0– 25.5 mm long, shortly glandular- and eglandular-pubescent externally especially on lateral lobes; tube 10.0– 12.5 mm long, widening slightly above insertion point of stamens, mouth 3.8–4.5 mm wide; limb 5-lobed, abaxial lobe only very slightly offset from other lobes by 1.0– 1.7 mm, broadly obovate, 10.5–11.0 × 8.0– 8.5 mm, apex emarginate, lateral lobes elliptic, 10.0–11.5 × 5.7–7.0 mm, apex rounded or emarginate, adaxial lobes as lateral lobes but narrower, 9.8–10.5 × 4.3–5.0 mm. Stamens inserted ± 5.5 mm from base of corolla tube, filaments ± 15.5 mm long, flattened and glandular-puberulent towards base; anthers exserted, 2.8–3.2 mm long; lateral staminodes 1.2–1.5 mm long, glandular-puberulent, adaxial staminode somewhat shorter. Ovary puberulent; style glabrous; stigma purple, linear, curved 1.6–1.8 mm long, with shallowly 2-lobed apex. Capsule 2-seeded, ± 11 mm long including prominent beak 4.5 mm long, eglandular-puberulent, hairs spreading or slightly antrorse; seeds only seen in immature state, 4 × 3 mm, with wavy cream-coloured hygroscopic hairs.

Distribution: — Swaziland, Lebombo Mountains, between the Umbeluzi River and Siteki ( Fig. 4 ).

Etymology: —Named after the Lebombo Mountains, a proposed sub-centre of endemism within the Maputaland Centre of Endemism ( Loffler & Loffler 2005).

Habitat and Ecology: —Both localities at which Barleria lebomboensis has been collected are situated in Southern Lebombo Bushveld within the Savannah Biome ( Mucina & Rutherford 2006). The type locality is in a mosaic of short, closed grassland on shallow, gravel soils with numerous low rhyolite outcrops and scattered dense, low evergreen thickets. This is the typical vegetation association on hilltops above 450 m elevation on the summit of the Lebombo range in Swaziland. The plants grow in grassland in full sun or in partial shade of low shrubs.

Conservation status: — Barleria lebomboensis is here assessed as Endangered EN B1ab(iii)+2ab(iii), following the Categories and Criteria of IUCN (2012). Justification for this assessment is the very small extent of occurrence of this species (estimated as a maximum of approximately 80 km 2 based upon modelling of its ecology), very small area of occupancy (estimated at less than 1 km 2), its occurrence at two locations and an inferred decline in habitat status through overgrazing and an increase in cultivation of summit grasslands within its range. The type locality is in the proposed Mhlumeni Community Conservation Area, an ecotourism initiative within the Lubombo Conservancy. However, this site does not have any formal conservation status at present and it is still heavily grazed. This species may also qualify as Endangered under Criterion C, but more complete population data are needed before this can be confirmed.

Taxonomic notes: —The combination of the prominently beaked, 2-seeded capsule, seeds with wavy pale hygroscopic hairs, the androecium comprising two fertile stamens and three small staminodes lacking antherodes, and the lack of axillary spines places this species in Barleria sect. Somalia (Oliver in Hooker 1886: t. 1528) Lindau (in Engler & Prantl 1895: 315) ( Balkwill & Balkwill 1997). On morphological grounds, Barleria lebomboensis belongs to Balkwill’s (1993) “Group 3” of sect. Somalia, which includes B. meyeriana and B. dolomiticola . The differences between these three species are considered in detail in Table 1, and are illustrated in Figs. 1–3 . Barleria lebomboensis is considered here to be most closely allied to B. meyeriana . It is usually easily separated from that species by the broadly ovate leaves, B. meyeriana usually having narrow, lanceolate leaves ( Fig. 3C ). Occasional ovate-leaved variants of B. meyeriana do occur (e.g. Germishuizen 5942 ex Swaziland, K!), but B. lebomboensis is still easily separated from these by the more dense indumentum throughout, the much more clearly defined and contracted inflorescence spikes, the smaller flowers and the densely puberulent capsules. The small, proportionately broad leaves and small puberulent capsules are reminiscent of B. dolomiticola , but the markedly different corolla form and size and the differing indumentum easily separate the two (see Table 1).

A further two species are listed in “Group 3” of Barleria sect. Somalia by Balkwill (1993): B. hirta Obermeyer (1933: 148) and B. pretoriensis Clarke (1901: 54) . These two species are very easily separated from B. lebomboensis by having narrow, lanceolate, narrowly oblong or linear leaves and larger corollas of 25–60 mm long, amongst other differences and so are not included in Table 1. Barleria hirta occurs in the Lebombo Mountains, but has so far not been recorded from the Swaziland portion of this range. That species also has glabrous or sparsely hairy capsules as in B. meyeriana .

Additional material studied (paratypes): — SWAZILAND. Blue Jay Ranch, 3.5 miles S of W entrance to Umbuluzi Gorge, Lubombo Mts. [1750 feet] 530 m, 10 April 1977, Culverwell 725 (K!, PRE).

Figures

FIGURE 1.—Barleria lebomboensis. A. Habit. B. Mature leaf, abaxial surface. C. Detail of stem indumentum. D. Pair of bracteoles and dissected calyx, with detail of indumentum. E. Flower in situ. F. Stamens and staminodes. G. Capsule valve, lateral and internal views. H. Seed. Drawn by Juliet Beentje, all from McCleland 1049 and associated photographs, except F from Culverwell 725. Scale bars:A = 3 cm; B, D, E, F = 2 cm; C, G, H = 4 mm.

FIGURE 2.—Photographs of Barleria lebomboensis in the field. A. Flower, face view. B. Inflorescence with open flower. C. Flower, lateral view. D. Inflorescence. E. Mature leaves. F. Habit and habitat.All taken by W. McCleland, Mhlumeni, Swaziland, 6 June 2016.

FIGURE 3.—Photographsof species allied toBarleria lebomboensis.A & B. Barleria dolomiticola, taken by W.Froneman,Lekgalameetse Nature Reserve Limpopo Province, South Africa, 1 March 2013. C & D. Barleria meyeriana, taken by W. Froneman, growing naturally in the Lowveld National Botanical Garden, Nelspruit, South Africa, 20 February 2013.

FIGURE 4.—Known and modelled distribution of Barleria lebomboensis.