Taxonomic treatment Open Access

Impatiens versicolor Eb. Fisch., Abrah., Holstein & S. B. Janssens 2021, sp. nov.

Fischer, Eberhard; Abrahamczyk, Stefan; Holstein, Norbert; Janssens, Steven B.

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

Holotype: Rwanda. Western Province, Nyungwe National Park, road 7 km south of Pindura towards Bweyeye, rocks and wet roadsides, 1800– 1900 m, 8 Mar 2013, E. Fischer 13390 (BR barcode BR0000014532108!; isotype: BONN!).

Diagnosis. – Impatiens versicolor belongs to the group with glabrous ovary. It differs from I. ludewigii in the white flowers, with occasionally single pink flowers appearing on the same plant, the dorsal petal divided to less than 1/3 of its length, the plants densely hairy on upper leaf surface, stems and pedicels, later glabrescent, the leaves at margin with 10– 15 pairs of extrafloral nectaries, and the often suberect habit.

Description. – Plants erect to suberect or ascending, usually glabrous or only with loose hairs, or sometimes densely hairy on upper leaf surface, stems and pedicels later glabrescent, stems 20–50 cm long. Leaves with 4–8 cm long petiole, petiole with 0–2 (4) pairs of extrafloral nectaries, lamina ovate, acuminate, 35–46 × 21–34 mm, margin with 10–15 pairs of extrafloral nectaries. Inflorescence with (1) 2 flowers, peduncle 5.5– 16.5 mm long, pedicel 11–18 mm long. Flowers white, petal base barely yellow, purple maculae at base large, occasionally single pink flowers appearing on the same plant. Lateral sepals 4.5–6.5 × 1–2 mm. Lower sepal navicular, 7–9 mm long and 3– 4.5 mm deep, abruptly constricted into a spiraled, usually filiform spur, 13–19 mm long. Dorsal petal divided to less than 1/3 of its length, 7–11 × 10.5–16.5 mm. Lateral united petals up to 23 mm long, upper lateral united petals 10–18 × 5–7.5 mm, not overlapping lower lateral united petals, base of upper lateral petal with dark pink or red and yellow maculae, lower lateral petal 13–19.5 × 5–7.5 mm. Ovary glabrous, 4– 5 mm long. Fruit glabrous, 13 × 6 mm. Figures 2, 6D–E, 15.

Ecology. – Wet rocks and roadbanks in montane rainforest, 1800–1900 m.

Distribution. – Rwanda, only known from Nyungwe National Park, only recorded in a valley south of Pindura towards Bweyeye.

Etymology. – Named after the occasional but regular colour change of single flowers from white to pink.

Published as part of 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, pp. 1273-1299 in TAXON 70 (6) on pages 1290-1292, DOI: 10.1002/tax.12566,
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