Introduction

Polygala L. (Linnaeus 1753: 701) is a genus with about 750 species (Paiva 2007) with a subcosmopolitan distribution (absent in New Zealand and arctic and Antarctic areas) and introduced in Polynesia and Greenland. The new species, P. kalaboensis Paiva, belongs to the subgenus Polygala, section Tetrasepalae Chodat (1893: 336) and subsection Hexandriae Paiva (1998: 288). Section Tetrasepalae is mainly characterised by having the two anterior sepals united for at least half their length, while in all other sections the five sepals are free. The main feature of subsection Hexandriae Paiva (1998: 288) is having 6 fertile stamens and two sterile ones (staminodes), while all other subsections have 8 fertile stamens. Sixteen species from Tropical Africa and two from Madagascar belong to subsection Hexandriae Paiva.

Taxonomic Account

Polygala kalaboensis Paiva, sp. nov. Type: Zambia, Kalabo, 15 Oct. 1963, Fanshawe 8089 (K, holotype).

http://www.ipni.org/urn:lsid:ipni.org:names:77150603-1

Procumbent shrublet or perennial herb, branched, with shoots up to 40 cm long. Stems arcuate-ascending, slender, glabrous. Leaves alternate, petiole 0.5 – 1 mm, glabrous, lamina obovate-oblong to spathulate-oblong, 1.5 – 2.5 × 0.4 – 0.7 cm, rounded at the apex with a recurved mucro, cuneate at the base, glabrous. Flowers purple-bluish, in terminal or pseudo-terminal simple racemes, few-flowered (up to 12 flowers), (3 –) 6 – 12 cm long; rachis glabrous; bracts linear-lanceolate, acute, 2 – 2.25 × 0.5 mm, ciliate, caducous; bracteoles linear, 0.5 – 1 mm long, ciliate, caducous; pedicels 2 – 3 mm, sparsely pubescent. Posterior sepal keel-shaped, 3.5 – 4 × 1 – 1.5 mm, ciliate; wing sepals obliquely ovate-elliptic, 9 – 10 × 3.5 – 4 mm, acute, 5-veined from the base, ciliate to glabrescent; anterior sepals keel-shaped, 3 × 1 mm, ciliate, connate. Upper petals obliquely obovate, 5 – 6 × 4 mm, rounded at the apex; carina 7 – 8 × 4 mm, ciliate at the base; crest 4 – 4.5 mm, fimbriate. Stamens 6, fertile with 2 staminodes. Capsule somewhat immature, oblong elliptic in outline 6 – 6.5 × 3 – 3.25 mm, notched, winged, wing 0.15 – 0.4 mm wide. Seeds immature, ellipsoid, 4 × 1.25 mm, with white, silky hairs; caruncle asymmetric kidney shaped, ± 1 mm long, hairy, appendages scarcely developed. Fig.1.

Fig. 1
figure 1

Polygala kalaboensis. A habit; B leaf, underside; C inflorescence detail; D young flower; E flower, showing petals; F posterior sepal, abaxial; G wing sepal, adaxial; H anterior sepals, abaxial; J pistil, stamens and staminodes; K young capsule; L immature seed. A – C from Fanshawe 8089; D – L from Drummond & Cookson 6483. drawn by juliet williamson.

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recognition. Polygala poggei Gürke, from Angola and Democratic Republic of Congo, is the closest species, but has shorter racemes (up to 6 cm long), with distinctive pubescent rachis and much smaller flowers (wing sepals 6 – 8 × 3 mm).

distribution. Endemic to Zambia. Map 1.

Map 1
figure 2

Distribution of Polygala kalaboensis.

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specimens examined. zambia. Kalabo, 15 Oct. 1963, Fanshawe 8089 (K!, holotype); Kalabo, W of Sikongo, 15 Nov. 1959, Drummond & Cookson 6483 (K!).

habitat. Kalahari sand in degenerate woodland with many cassava patches.

conservation status. Data Deficient (DD). Little is known about the true distribution of this species. It is here described from only two herbarium collections and locality information is only available for one of them (Drummond & Cookson 6483). Pope & Pope (1998) place Drummond & Cookson collections from 1959 at the following location: Kalalo 14°57'S 22°40'E. Kalabo is a district in the Western Province of Zambia, less than 100 km from the Angolan border. It is an area near floodplains, covered by Zambezi river waters during the rainy season. North of Kalabo there is a protected area called Liuwa Plains National Park. However the specimen appears to have been collected outside this protected area. This is one of Zambia’s less populated areas where development pressure is likely to be low. The only possible threat to its native vegetation is the one posed by cattle grazing, a common activity in this area (Timberlake, pers. comm. September 2014 ). More fieldwork in this region is required to fully understand the distribution of this species and the size of the population, as well as any threats. The lack of data leads to uncertainty in regard to Red List conservation rating. It could plausibly be a restricted range species qualifying under Criterion B or D, but it could equally be possible that the area could support a healthy population under no particular threat that would warrant a Least Concern or Near Threatened category at most. As a result, according to IUCN categories and criteria (2012), this species is assessed as Data Deficient (DD).

notes. There are four species of the section Tetrasepalae which have similar morphologies. However, they all have features which distinguish them as shown in Table 1. All species are procumbent shrublets or perennial herbs sending up annual shoots, sparsely pubescent to glabrescent in Polygala homblei Exell and P. luteo-viridis Chodat or glabrous in P. poggei and P. kalaboensis. P. kalaboensis and P. homblei are the species with larger flowers, but P. homblei has 8 fertile stamens, narrower leaves and shorter racemes than P. kalaboensis, which has only 6 fertile stamens. P. poggei has smaller flowers and shorter racemes with a pubescent rachis whereas P. kalaboensis has a glabrous rachis. P. luteo-viridis has more flowers per raceme and smaller flowers. P. poggei is the only one of this group which is greenish when dried, similar to P. dewevrei Exell, another species with 6 stamens (subsection Hexandriae), which has subcapitate, lateral racemes, while the racemes of P. poggei are terminal and lateral, not subcapitate.

Table 1 Comparative features of four species of Polygala, section Tetrasepalae.
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