Endostemon palustris A.J.Paton & Goyder, 2023

Goyder, David J., Davies, Nina, Finckh, Manfred, Gomes, Amandio, Goncalves, Francisco Maiato P., Meller, Paulina & Paton, Alan J., 2023, New species of Asclepias (Apocynaceae), Baphia (Leguminosae), Cochlospermum (Bixaceae) and Endostemon (Lamiaceae) from the Kalahari sands of Angola and NW Zambia, with one new combination in Vangueria (Rubiaceae), PhytoKeys 232, pp. 145-166 : 145

Endostemon palustris A.J.Paton & Goyder sp. nov.

Diagnosis.

Differs from E. tubulascens (Briq.) M.Ashby in the little-branched habit, the sessile rather than petiolate and linear rather than elliptic leaves, the fewer-flowered (4-6-flowered rather than 6-10-flowered) verticils in the inflorescence, the pale violet rather than pinkish white flowers and the longer calyx (fruiting calyx 8-9 mm long rather than 5.5-6 mm).

Type.

Angola. Moxico Province: Confluence of Cuito River and its 1st tributary, the Kalua River , c. 65 km SSW of Munhango, 12°44'55"S, 018°21'16"E, fl. 20 Oct. 2016, D.Goyder & F.Maiato 8762 (holotype: K (K001333409); isotypes: INBAC, LUBA) .

Description.

Aromatic perennial suffrutex with few stems arising from a thick woody rootstock; stems erect, 15-30 cm tall, branched near the base, square in section above, more rounded below, pubescent with both glandular and eglandular hairs. Leaves verticillate, ascending, sessile, linear and folded along the midvein, 2.5-5 cm long, 0.1-0.2 cm wide, pubescent. Inflorescence lax with 4-6-flowered verticils 1.5-2.5 cm apart; bracts lanceolate or narrowly ovate, 3.5-4.5 mm long; pedicels 1-5 mm long, longer in lower verticils. Calyx 5 mm long at anthesis, pubescent with spreading hairs and sessile glands, posterior lip purplish; fruiting calyx 8-9 mm long. Corolla pale violet, 8-10 mm long; tube 6-7 mm long, straight, parallel-sided, dilating at the throat. Filaments c. 0.5 mm long, glabrous or pilose. Ovaries pubescent at apex. (Fig. 4 ).

Distribution and ecology.

Known only from the type collection close to the source of the Cuito River. It was found towards the upper edge of a marsh fringing the river. (Map 3 ).

Conservation status.

Although known from a single locality, Endostemon palustris occupies a habitat that is extensive within the upper catchment of the Cuito and its tributaries. The area is not threatened with agricultural development being both nutrient poor and many kilometres from any human habitation, but with so little information the species is provisionally assessed as Data Deficient.

Taxonomic notes.

Endostemon N.E.Br. is an isolated genus of 20 species within the tribe Ocimeae, with two centres of endemism - Angola and the Horn of Africa. It can be recognised within the Orthosiphon Benth. group of genera by its short, villous staminal filaments, an expanded shield-like base to the style, and pollen with alternating wide and narrow mesocolpia ( Paton et al. 1994; Ryding et al. 2003; Paton et al. 2004). With the exception of E. tereticaulis (Poir.) M. Ashby which is in Endostemon sect. Oblongi Ayob. ex A.J.Paton, Harley & M.M.Harley, all of the Angolan species fall within Endostemon sect. Endostemon . This section is characterised by a relatively short calyx tube with an open glabrous throat, and the form of the lateral calyx lobes - the posterior margins of these lobes are not extended towards the upper lip of the calyx. Endostemon tubulascens , to which this new species is compared, appears largely restricted to the high escarpment zone around Lubango, Huíla Province, Angola.

Figures

Map 3. Known distribution of Endostemon palustris (star), and of the related species E. tubulascens (cross).

Figure 4. Endostemon palustris A habit B flower C opened corolla showing androecium and gynoecium D base of gynoecium showing three of the four nutlets and the gynobasic style E individual nutlet F calyx G indumentum. Drawn by Margaret Tebbs from Goyder & Maiato 8762.