Streptocarpus schaijesii Eb.Fisch. & I.Darbysh., 2021

Fischer, Eberhard & Darbyshire, Iain, 2021, Five new species of Streptocarpus (Gesneriaceae) from Katanga, D. R. Congo, Plant Ecology and Evolution 154 (2), pp. 264-280 : 276-277

Streptocarpus schaijesii Eb.Fisch. & I.Darbysh. , sp. nov.

( figs 7 , 8 , 9B ) –

Type: D.R. CONGO – Haut Katanga • à 53 km SW de Kolwezi, Musokatanda , près des chutes de la Lofupa , rocher couvert des mousses en galerie forestière; 1200 m; 25 Dec. 1982; Schaijes 1695; holotype: BR [ BR0000016803411 ].

Diagnosis – The species differs from Streptocarpus michelmorei in the pale lilac corolla lacking a deep violet patch on the palate and behind, in the corolla tube being only slightly curved and scarcely deepened on the lower side at the middle, and in the distinctly shorter capsule. The species differs from Streptocarpus solenanthus in usually having a shorter corolla tube and in the longer lower lip of the corolla. It differs from Streptocarpus bampsii in the slightly curved and longer corolla tube, the longer corolla lower lip and the longer staminodes.

Description – Monocarpic acaulescent herb. Unifoliate, lamina broadly ovate to nearly orbicular, 10–25 × 9–19.9 cm, base shallowly cordate, margin crenate-dentate, apex obtuse, usually withered, pubescent on upper and lower surface, with 12–17 pairs of lateral nerves, petiolode not exceeding 1 cm long, pubescent. Inflorescences 1–2 per plant, arising from the petiolode, peduncle up to 9.5(–14) cm long, pubescent. Pedicels 12–19 mm long, eglandular pubescent, bracts linear-lanceolate, up to 5 mm long. Calyx divided to base, lobes lanceolate, 3–6 mm long, hairs on calyx eglandular. Corolla dark violet to blue, lobes of almost the same colour as the tube, 25–43 mm long, densely eglandular-pubescent, glabrous within, tube slightly curved, only slightly expanded towards mouth, (15–)22–35 mm long, 3–5 mm in diameter, 6–7 mm towards mouth, limb bilabiate, upper lip of two rounded lobes, 3–6 × 3–5 mm, lower lip of 3 rounded lobes, 6–11 × 4–6 mm, lateral lobe 6 × 4–6 mm, median lobe 6–11 × 6 mm. Stamens inserted in upper third of corolla tube towards mouth, filaments 7 mm long, glabrous, anthers white, 2–3 mm long, staminodes inserted below stamens, 1.5–2 mm long. Ovary densely eglandular-pubescent, ovary and style 15–20 mm long. Capsules 45–65 × 1.5–2 mm, eglandular-pubescent.

Distribution – Endemic to D.R. Congo, Haut Katanga.

Habitat – Humid, calcareous rocks in gallery forest or ravine near waterfall, 1200–1650 m elevation.

Etymology – Named after Michel Schaijes, who made major contributions to the knowledge of the flora of Katanga, and who collected the type.

IUCN conservation assessment (preliminary) – Endangered: EN B2ab(iii). Streptocarpus schaijesii is known from 8 herbarium collections comprising 5 localities. The estimated AOO is 20 km 2 (assuming a 4 km 2 grid cell size). The habitat of gallery forest is under potential threat of logging. Thus, the species could be preliminarily assessed as Endangered: EN B2ab(iii).

Additional specimens studied – D.R. CONGO – Haut Katanga • Lubumbashi–Likasi, km 50, riv. Kamianga, Thalweg de ravin boisé; 11°18′S, 27°17′E; 1335 m; 15 Jan. 1986; Bamps & Malaisse 8026; BR[BR0000016803428] • Luita, forêt dense de ravin, sur un bloc rocheux; 10°44′S, 26°18′E; 1500 m; 4 Apr. 1986; Malaisse 13820; BR[BR0000016803404] • Biano, au 22,8 km au N de Temke, sur la piste de la ferme Scholls, sur termitière; 1650 m; 26 Mar. 1984; Schaijes 2282; BR[BR0000016803398] • Route carrefour Likasi-Kambove et bifurcation Mindigi, Kakontwe, paroi verticale de calcaire; 27 Mar. 1986; Malaisse 13809; BR[BR0000016803497] • Calcaire de Kakontwe; 2 Apr. 1981; Malaisse 11761; BR[BR0000016803503] • Kakontwe, affleurement calcaire, paroi verticale ombragé; 3 Oct. 1979; Malaisse 9956; BR[BR0000016803510] • à 5 km au N de Kakontwe, chandelle calcaire, au paroi rocheuse vertical; 30 Jan. 1980; Malaisse 10213; BR[BR0000016803350] .

Taxonomic notes – Streptocarpus bampsii , S. malaissei , S. salesianorum , and S. schaijesii are morphologically close and apparently related to Streptocarpus michelmorei B.L.Burtt ( Burtt 1939: 72) and S. solenanthus Mansfeld ( Mansfeld 1934: 96) in Streptocarpus agg. cooperi of Hilliard & Burtt (1971). They have eglandular hairs on the pedicel, calyx, and corolla, and the limb is small in relation to the tube, with a lower lip not exceeding 15 mm of length. Hilliard & Burtt (1971) assigned some taxa to the S. michelmorei complex, where they distinguished two species from Malawi (7A Streptocarpus sp. S. michelmorei affinis) and Zambia (7B Streptocarpus sp. S. michelmorei affinis). Despite the overall similarities, several distinct entities can be distinguished which are described here as new species. One taxon from this aggregate, Streptocarpus mbeyensis I.Darbysh. ( Darbyshire 2006: 39) has already been described. For a comparison of the species see table 2 .

Wild-collected material assigned to S. michelmorei appears to be rather more variable than the type material. Hilliard & Burtt (1988) suggests that plants from Bridal Veils Falls in the Chimanimani Mts of Zimbabwe (e.g. Bamps, Symoens & Vandenberghen 770, BR0000016801868, BR0000027611722V) may be intermediate between S. michelmorei and S eylesii S.Moore, stating that the deep corolla colouration and slender fruits are close to S. michelmorei but that the distinctly curved corolla tube and larger median lobe suggest the influence of S. eylesii . However, the Bridal Veils Falls plants have a short eglandular indumentum on the inflorescence, whilst both S. michelmorei and S. eylesii usually have a glandular component to their inflorescence indumentum, casting doubt over Burtt’s theory that this is a hybrid population.

Figures

Figure 7 – Streptocarpus schaijesii. A–B. Habit. C–D. Partial inflorescence. E. Flower, lateral view. F. Corolla dissected, showing position of stamens and staminodes. G. Stamens. H. Staminode. A, C–H from Schaijes 1695 and B from Malaisse 13809. Illustration by Eberhard Fischer.

Figure 8 – Streptocarpus schaijesii. A, C, E. Habit. B, D. Flower. Photographs taken by Michel Schaijes at Musokatanda (A–C, Schaijes 1695) and Biano, Temke (D, E, Schaijes 2282). © Michel Schaijes, all rights reserved.

Figure 9 – A. Distribution map of Streptocarpus malachiticola, S. bampsii, and S. salesianorum. B. Distribution map of S. schaijesii and S. malaissei. Map created using ArcMap 10.8 (https://www. arcgis.com). © Esri and its licensors, all rights reserved.