Impatiens purpureoviolacea Gilg

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 : 1282

Impatiens purpureoviolacea Gilg in Bot. Jahrb. Syst. 43: 122. 1909 –

Holotype: Rwanda. Rugege-Wald, Rukarara , c. 1900 m, mid-Aug 1907, J. Mildbraed 912 (B barcode B 10 0153415 !; isotype: B barcode B 10 0153416 !).

Description. – Plants prostrate to ascending, stems 10–25 (80) cm long. Leaves dark green above, light green below, petiole (3) 4–13 (18) mm long, with (0) 1–2 pairs of extrafloral nectaries, leaf lamina (25) 27–51.5 (59) × (14) 20–36 mm, broadly ovate or lanceolate, obtuse at apex, margin with 10–24 (28) pairs of extrafloral nectaries. Inflorescence with 1–2 flowers, peduncle 9–20 mm long, pedicel 7–14 mm long. Flowers pink, petal base barely yellow, purple maculae at base large but sometimes ± hidden in throat, Lateral sepals 4–6.8 × 1.2–2.2 mm. Lower sepal navicular, abruptly constricted into a spiraled, usually filiform spur, 6–8 mm long and 3–5 mm deep, spur 5–17 mm long. Dorsal petal 7.5–10.5 (12) × (10) 12–16 mm. Lateral united petals with upper lateral petal (7) 10–13 × 5–9 mm, bent or curved upwards, not largely overlapping with lower lateral petals, lower petal 13–17 × 6–9 mm, oblong-elliptical. Ovary white pilose, 3–4 mm long. Fruit white pilose, 12–17 × 4.5– 7 mm. Figures 2 , 4A,B , 7 , 11A–E .

Ecology. – Montane rainforest, 1900–2540 m.

Distribution. – Rwanda: Nyungwe National Park.

Specimens examined. – Rwanda. Lacs Edouard et Kivu. Western Province, Nyungwe National Park, environs d’ Uwinka, 2400 m, 20 Jan 1971, Bouxin 50 (BR) ; Forêt de Nyungwe, environs d’ Uwinka, 2400 m, 23 Jan 1971, Bouxin 129 (BR) ; environs de Rwankuba, 1900 m, 10 Mar 1971, Bouxin 368 (BR) ; Forêt de Nyungwe, environs d’ Uwinka, 2400 m, 13 Mar 1971, Bouxin 454 (BR) ; Forêt de Nyungwe, environs d’ Uwinka, 2000–2400 m, 9 Aug 1969, Bouxin & Radoux INRS 552 (BR) ; Rwankuba, 18 Dec 1971, Bamps 2804 (BR) ; entre Pindura et l’ Ibigugu, 2540 m, 29 Jul 1974, Auquier 3514 (BR) ; route Astrida (= Butare, Huye)–Bukavu, env. d’ Uwinka, 2300 m, 19 Dec 1959, Troupin 11440 (BR) ; route Astrida (= Butare, Huye)–Bukavu, km 93, env. d’ Uwinka, 2150 m, 29 Dec 1959, Troupin 11462 (BR) ; route Astrida (= Butare, Huye)–Bukavu, vers km 93, environs d’ Uwinka, colline Bunyangurube, 24 Feb 1960, Troupin 11909 (BR) ; route Bukavu–Astrida (= Butare, Huye), vers km 93, environs d’ Uwinka, colline Bunyangurube, 27 Apr 1960, Troupin 12205 (BR) ; route Bukavu–Astrida (= Butare, Huye), km 93 colline Uwinka, 2450 m, 3 Jun 1960, Troupin 12338 (BR) ; km 90 route Bukavu–Astrida (= Butare, Huye), 2000 m, 6 Jun 1959, Michel 6342 (BR) ; Kamiranjovu (= Kamiranzovu), 2000 m, 17 Mar 1956, Christiaensen 1375 (BR) ; Kamiranjovu (= Kamiranzovu), 2000 m, 17 Mar 1956, Christiaensen 1376 (BR) ; Nyungwe National Park, Uwinka, E. Fischer 8093, Oct 1999 (KOBL) ; Rukarara, source of the Nile, 2250 m, 20 Mar 2013, E. Fischer 12855 (KOBL) ; Rukarara, Source of the Nile, 2250 m, 7 Jan 2015, E. Fischer 13911 (KOBL) ; Karamba, 1900 m, 21 Mar 2013, E. Fischer 12958 (KOBL) ; Karamba, 1900 m, 7 Oct 2013, E. Fischer 13018 (KOBL) ; Karamba, 1900 m, 7 Jan 2015, E. Fischer 13910 (KOBL) ; Southern Province, Nyamagabe (= Gikongoro), Nyungwe National Park, Commune Kivu, savane de Nyabihu, 2 Aug 1999, Ewango 2163 (BR) .

Notes. – Grey-Wilson (1980) lists the type locality erroneously from the eastern Democratic Republic of the Congo (“Eastern Zaire”). The Rukarara is one of the sources of the Nile and now situated in Nyungwe National Park, Rwanda. Impatiens purpureoviolacea s.str. is confined to Nyungwe Forest and could not be recorded in Gishwati-Mukura National Park or in the Volcano National Park, the former Albert National Park that continues in the eastern Democratic Republic of the Congo (Virunga National Park) and southwestern Uganda (Mgahinga National Park). Despite the overall floristic similarities between Nyungwe and Bwindi Impenetrable Forest in southwestern Uganda, I. purpureoviolacea has also never been recorded there.

Figures

Fig. 2. Distribution map of the eight insect-pollinated species of the Impatiens purpureoviolacea complex. Dots indicate species with hairy ovaries, and stars mark species with glabrous ovaries.

Fig. 4. Seeds of the Impatiens purpureoviolacea complex. A & B, Impatiens purpureoviolacea: A, Seed; B, Detail of testa. C & D, Impatiens lutzmannii: C, Seed; D, Detail of testa. E & F, Impatiens urundiensis: E, Seed; F, Detail of testa. — Scale bars: A, 300 μm; B, 60 μm; C, 500 μm; D, 80 μm; E, 500 μm; F, 90 μm. A & B, Fischer 12958, BG Bonn 36240; C & D, Fischer 13002, BG Bonn 33486; E & F, Fischer 13301, BG Bonn 35170.

Fig. 7. Impatiens purpureoviolacea. A, Habit; B, C & E, Flower, frontal view; D & F, Flower, lateral view. — A, B & D, Fischer 13911, Rwanda, Nyungwe National Park, source of Rukarara; C, Fischer 12958, Rwanda, Karamba; E & F, Fischer 8093, Rwanda, Uwinka.

Fig. 11. A–E, Impatiens purpureoviolacea. A, Flower; B, Lower sepal and spur; C, Dorsal petal; D & E, Lateral united petals. F–I, Impatiens lutzmannii. F, Flower; G, Lower sepal and spur; H, Dorsal petal; I, Lateral united petals. J–N, Impatiens urundiensis. J, Flower; K, Petiole, lateral sepals and anthers; L, Lower sepal and spur; M, Dorsal petal; N, Lateral united petals. — Scale bar: 1 cm. A–E, Fischer 13911, Rwanda, Rukarara; F–I, Fischer 13002, Burundi, Kumuyange; J–N, Fischer 13301, Burundi, Kumuyange.