Impatiens ludewigii Eb.Fisch., Abrah., Holstein

Fischer, Eberhard, Abrahamczyk, Stefan, Holstein, Norbert & Janssens, Steven B., 2021, Evolution of Impatiens (Balsaminaceae) in the Albertine Rift - The endemic Impatiens purpureoviolacea complex consists of ten species, TAXON 70 (6), pp. 1273-1299 : 1288

Impatiens ludewigii Eb.Fisch., Abrah., Holstein & S.B.Janssens, sp. nov.

– Holotype: Rwanda. Western Province, Nyungwe National Park, near Uwinka on trail to canopy walkway, 1990 m, 4 Mar 2016, E. Fischer 14500 ( BR barcode BR0000014532122 !; isotypes: BONN!, KOBL!).

Diagnosis. – Impatiens ludewigii belongs to the group with glabrous ovary. It differs from I. versicolor in the always pink flowers, the dorsal petal divided to more than 1/3 up to 1/2 of its length, the plants hairy on upper surface of young leaves, later glabrescent, the leaves at margin with (16) 23–29 pairs of extrafloral nectaries, and the plants being usually prostrate to ascending.

Description. – Plants prostrate to ascending, usually glabrous or only with loose hairs, stems 10–50 cm long. Leaves hairy on upper surface of young leaves, later glabrescent, petiole (3) 6–13 mm long, with 1–2 (4) pairs of extrafloral nectaries, lamina 18–55 (99) × 14–33 mm, margin with (16) 23– 29 pairs of extrafloral nectaries. Inflorescence with 1–2 (3) flowers, peduncle (3) 6.5–10 (13) mm long, bracts 2–3 × 0.5 mm, pedicel glabrous, 12–23 mm long. Flowers pink, petal base barely yellow, purple maculae at base large. Lateral sepals 5–5.5 × 1.5–2 mm, with long simple trichomes. Lower sepal navicular, 6–9.5 mm long and 3–5 mm deep, abruptly constricted into a spiraled, usually filiform spur, spur (11) 16– 20 mm long. Dorsal petal divided to more than 1/3 up to 1/2 of its length, 7–9 (11) × (6) 12–14.5 mm. Lateral united petals 19 mm long, upper lateral petals (7) 10–18 × (4) 6–7.5 mm, not overlapping lower lateral united petals, base of upper lateral petal with dark pink or red and yellow maculae, lower lateral petal (10) 16–16.5 (18) × (4) 6.5–7 mm, distinctly elongate. Ovary 3–4 mm long, glabrous. Fruit 12–16 × 4–5.5 mm, glabrous. Figures 2, 6A–C, 12.

Ecology. – Montane rainforest, 1700–2300 m.

Distribution. – Democratic Republic of the Congo, Kahuzi-Biéga National Park; Rwanda, Nyungwe National Park.

Etymology. – Named after the counselor of the University of Koblenz-Landau, Michael Ludewig.

Specimens examined. – Democratic Republic of the Congo. Lacs Edouard et Kivu. Montagnes à l’ ouest du Lac Kivu , Massif du Kahuzi , vers 2000 m, Mar 1929, Humbert 7755 ( BR, P) ; km 45 route Kavumu-Buniakiri , Bitale , 18 Apr 1951, 1820 m, Pierlot 134 ( BR) ; contreforts du Mt. Kahuzi , 6 Apr 1956, 2100 m, Pierlot 1277 ( BR) . Rwanda. Lacs Edouard et Kivu . Western Province, Nyungwe National Park. Env. de Rangiro , Rutabanzogera , 1700 m, 11 Feb 1980, Bridson 377 ( BR) ; 2 km avant Gisakura ( venant de la route Butare– Cyangugu ), 24 Aug 1974, Van der Veken 10967 ( BR) ; route Bukavu–Astrida , env. Uwinka , colline Bunyereri , 2100 m, 9 Jul 1960, Troupin 12436 ( BR) ; env. de Wisumo , centre forestier Suisse , 2150 m, 21 Feb 1974, Troupin 14453 ( BR) ; talus humide de la route Bukavu–Astrida (= Butare, Huye ), à env. 27 km à l’ E de Shangugu (= Cyangugu , Rusizi ), 1930 m, 7 Feb 1958, Symoens 5369 ( BR) ; Kamiranjovu (= Kamiranzovu ), 2000 m, 17 Mar 1956, Christiaensen 1376bis ( BR) ; Uwinka , 2300 m, 22 Oct 2013, E. Fischer 10280 ( KOBL) ; Uwinka , 2300 m, 27 Oct 2013, E. Fischer 10350 ( KOBL) ; Gisovu , 2200 m, 7 Jan 2015, E. Fischer 13914 ( KOBL) ; Uwinka , 2300 m, 4 Mar 2016, E. Fischer 14489 ( BR, BONN, KOBL) ; Uwinka , 1750 m, 4 Mar 2016, E. Fischer 14500 ( BONN, BR, KOBL) .