Barleria thunbergiiflora I.Darbysh.

Darbyshire, Iain, Manzitto-Tripp, Erin A. & Chase, Frances M., 2021, A taxonomic revision of Acanthaceae tribe Barlerieae in Angola and Namibia. Part 2, Kew Bulletin 76 (2), pp. 127-190 : 164-166

51. Barleria thunbergiiflora I.Darbysh. sp. nov.

Type: Angola, Moxico Prov., confluence of Cuito R. and Calua R. , fl. 25 Feb. 2016, Goyder 8343 (holotype K! [ K001333932 ] ; isotypes INBAC, LUBA, PRE !).

http://www.ipni.org/urn:lsid:ipni.org:names:77215732-1

Barleria benguellensis sensu Benoist (1950: 18) , pro parte quoad Exell & Mendonça 1345, non S. Moore (1911: 305) — see note.

Suffruticose herb, with erect unbranched or fewbranched stems 30 – 50 cm tall from a woody base, this sometimes shortly rhizomatous, with numerous fleshy roots; stems 4-angular, with short white antrorse or appressed hairs concentrated in two opposite bands, or these sparse (possibly glabrescent on mature stems). Leaves sessile or petiole to 2 mm long; blade somewhat coriaceous, held erect or ascending, largest cauline leaves ovate, elliptic or obovate, 4.4 – 7.8 × 2 – 4.3 cm (l:w ratio 1.3 – 2.5: 1), base cordate, rounded or obtuse to cuneate or attenuate, margin entire, apex obtuse to rounded, apiculate, surfaces glabrous or with few pale hairs along midrib beneath; lateral veins 4 – 8 pairs, these and fine reticulate tertiary venation prominent on both surfaces. Inflorescences of opposite single-flowered cymes aggregated into loose spikes 5 – 15 cm long; bracts foliaceous but rapidly reducing upwards, those towards stem apices ovate, oblongelliptic or somewhat -obovate, 12.5 – 30 × 8 – 15 mm, base shallowly cordate to cuneate; cymes at lowermost fertile axils on peduncle 9 – 19 mm long, peduncles shortening distally where 2.5 – 5 mm long; bracteoles ± tightly conduplicate and clasping calyx base, ovate to lanceolate or elliptic to oblanceolate, 13.5 – 28 × 5.5 – 12 mm, glabrous; pedicels 2 – 4 mm long, palepuberulous. Calyx pale yellowish green with reddish, purple or purple-brown tinge towards or along margins and/or in distal half, somewhat accrescent; anterior lobe broadly ovate, 23 – 27 × 16.5 – 21 mm in flower, up to 31 × 23.5 mm in fruit, base rounded to cordate, margin entire, often involute, apex very shallowly notched or obtuse to rounded, external surface glabrous, with prominent palmate venation, internal surface finely appressed-puberulous; posterior lobe as anterior lobe but 24.5 – 30 × 17.5 – 21 mm in flower, up to 32.5 × 26 mm in fruit, apex obtuse or rounded, apiculate; lateral lobes pale green, lanceolate-attenuate, 14 – 15 mm long, puberulous. Corolla 42 – 53 mm long, lilac-blue, glabrous externally; tube 17 – 19 mm long, cylindrical below insertion point of stamens, markedly funnel-shaped above, mouth c. 12 mm in diam.; limb in “4+1” configuration, abaxial lobe offset by 3.5 – 5.5 mm, broadly obovate to obovate-orbicular, c. 21.5 × 18.5 mm, apex rounded or slightly emarginate, lateral lobes obovate-elliptic, 23 – 25.5 × 18 – 21 mm, adaxial lobes somewhat narrower, 19.5 – 25 × 16 – 18 mm. Stamens inserted c. 7 mm from base of corolla tube; filaments 17 – 18.5 mm long, with subsessile glands throughout and glandular-puberulous at base; anthers c. 5 mm long, shortly exserted; lateral staminodes 2 – 3 mm long. Pistil glabrous; stigma linear, 2.9 – 4.5 mm long, curved. Capsule 4-seeded, 23 – 24.5 mm long including beak ± 5 mm long, glabrous; seeds ± 7.5 – 8 × 6.5 mm. Figs 7E – G & 9 .

RECOGNITION. Barleria thunbergiiflora is most closely allied to B. kacondensis , with which it shares a large corolla with a broadly funnel-shaped tube and glandular staminal filaments. It differs in having ovate or elliptic to obovate leaves, with l:w ratio 1.3 – 2.5: 1, held erect or ascending (vs leaves spreading, oblongelliptic to lanceolate, l:w ratio 3.3 – 8.4: 1), in the corolla being blue-lilac (vs white to pale pink) and in having broader calyces with a more broadly obtuse or rounded apex to the posterior lobe (vs usually acute or attenuate in B. kacondensis ). It additionally differs from B. kacondensis subsp. kacondensis in being largely glabrous (vs coarsely hairy throughout) and in the plants being less widely branched. Vegetatively, this species most closely resembles B. eburnea but it is easily separated by the much larger, blue-lilac flowers 42 – 53 mm long, with longer staminal filaments 17 – 18.5 mm long that are glandular throughout (vs corolla white to pale yellow, 28 – 31 mm long, staminal filaments 6.5 – 8 mm long, glabrous except at the base in B. eburnea ); B. eburnea also has narrower, subulate to oblancelate bracteoles that are markedly arcuate.

DISTRIBUTION. Endemic to Eastern Angola (Lunda Sul and Moxico Provs.); Map 4 .

ADDITIONAL COLLECTION STUDIED. ANGOLA. Lunda Sul Prov., Biula, R. Cassai [Kasai], old infl. 28 April 1937, Exell & Mendonça 1345 (BM!, P*) — see note; Moxico Prov., upper Lungue Bungu river valley 77 km SE of Cuemba and 48 km S of Munhango, fr. 25 April 2018, Goyder 8952 (INBAC, K!, LUBA!, PRE!).

HABITAT & ECOLOGY. Barleria thunbergiiflora occurs in open grassland rich in geoxylic suffrutices on deep Kalahari Sands on plateaux above rivers, and in seasonal marshes (“tengas”) at 1190 – 1400 m alt. It appears to occur on more nutrient-poor sites than most of the allied species in sect. Somalia.

CONSERVATION STATUS. This species is currently known from three localities, two of which are in close proximity in western Moxico Province. The third locality is over 200 km to the northeast of the Moxico sites, in southern Lunda Sul Province. However, the area of Angola in which it occurs is one of the least well botanised regions of continental Africa (see Discussion) and its range is likely to be larger than currently known given the fact that its preferred habitats are widespread there. Of the two populations found by D. Goyder (pers. comm.), only a single patch of this species was found at the type locality, but at the second locality (his collection 8952) the population was much larger and scattered over several kilometres. The perched valley-grasslands on sand that this species occupies are nutrient-poor and are not suitable for agriculture, so there are no obvious threats. Increased frequency of burning, observed in some areas (D. Goyder, pers. obs.), may result in gradual ecological changes over time but the human population remains low within much of its range at present. It is therefore assessed as of Least Concern — LC.

ETYMOLOGY. The species epithet “ thunbergiiflora ” refers to the fact that the flowers of this species superficially resembles the genus Thunbergia in having large, funnel-shaped corollas and in the large calyx lobes resembling the conspicuous paired bracteoles in Thunbergia . Indeed, the type specimen of this plant was first identified as a Thunbergia in the field.

NOTES. Exell & Mendonça 1345 from the Kasai River along the Lunda Sul-Moxico provincial border is close to the other material of this species, although the leaves and bracts are obovate (but note that in Goyder 8952 some of the stems have equally obovate leaves) and the bracteoles are larger, less markedly conduplicate and more oblong or oblanceolate. This specimen only has old, empty calyces and it would be desirable to collect flowering material from that location to confirm that it belongs here.

The close relationship between Barleria thunbergiiflora and B. kacondensis , inferred from morphological evidence, has recently been confirmed by RADseq phylogenetic analysis ( Comito 2019). The two species are readily separated by the characters given in the Recognition section; B. thunbergiiflora appears to replace B. kacondensis in the more nutrient-poor soils of eastern Angola.

Figures

Map 4. Distribution of Barleria antunesii (grey stars), B. kacondensis subsp. kacondensis (black circles), B. kacondensis subsp. glabrescens (yellow diamonds), B. thunbergiiflora (blue squares), B. sp. (= Teixeira s.n.) (white-centred black circle) and B. eburnea (red triangles).

Fig. 7. A – D Barleria kacondensis subsp. kacondensis. A habit; B flower; C inflorescence; D detail of inflorescence node. E – G Barleria thunbergiiflora. E habit, fruiting; F habit, flowering; G flower. A, C collected as Goyder 8493, E as Goyder 8952, F, G as Goyder 8343. PHOTOS: A, C, E – G D. J. GOYDER; B, D F. M. P. GONÇALVES (ALL IMAGES ANGOLA).

Fig. 9. Barleria thunbergiiflora. A habit; B mature leaf,obovatevariant;C leaf apex showing apiculum,adaxial surface;D detail of reticulateleaf venation,abaxial surface; E indumentum of youngstem; F detail of stem hairs;G calyx andsubtending bracteoles;H lateral calyx lobe,(right) at same scaleas calyxandbracteolesand(left)blownuptoshowindumentum;J flower,faceview;K dissected corollawithandroecium;L detailof staminodes and staminal filament bases; M detail of glandular hairs on mid/upper portion of staminal filaments; N hairs from staminode; P hairs from staminal filament base. A, C – J, K – P from Goyder 8343, B from Exell & MendonÇa 1345; J from photograph taken by D. Goyder.DRAWN BY ANDREW BROWN.