Impatiens smetsiana S.B.Janssens, Taedoumg & Dessein, 2022

Janssens, Steven B., Taedoumg, Hermann & Dessein, Steven, 2022, Impatiens smetsiana, another example of convergent evolution of flower morphology in Impatiens, Plant Ecology and Evolution 155 (2), pp. 248-260 : 248

Impatiens smetsiana S.B.Janssens, Taedoumg & Dessein sp. nov.

Figs 1 , 4

Type.

CAMEROON - Adamawa Region • Chabal Mbabo ; 7°13 ’54” N, 12°5 ’57” E; 8 May 2009; Dessein S. & Taedoumg H. 2950; holotype: BR [BR0000024941891]; isotype: L [L.4446681], YA, WAG .

Diagnosis.

Impatiens smetsiana belongs to the Equatorial West African Impatiens lineage. It differs from I. kamerunensis , I. filicornu , and I. nzabiana in having an elliptic leaf shape, no leaf fimbriae, an oblong-shallowly cucullate dorsal petal shape, and an asymmetric obovate lower lateral petal shape.

Description.

Erect perennial herb up to 60 cm tall. Stems simple or branched, glabrous. Leaves spirally arranged; petiole 2-6.3 cm long; leaf blades 7.5-11 × 3.7-5.5 cm, ± elliptic, attenuate at the base, ± acuminate at the apex, glabrous; lateral veins 5-7 at each side of the midrib; leaf margins crenate without short filiform fimbriae at the base. Flowers in 6 to many flowered subumbellate racemes; pedicels 15-21 mm long, slender, glabrous; bracts green with red tips; ovate, 5-6 × 4-5 mm. Lateral sepals 2, green, 3.8-4.5 mm, ovate, glabrous. Lower sepal pink, 8-9 × 7-7.5 mm, narrowly and obliquely navicular, abruptly constricted into a 23-35 mm long curved filiform white spur. Dorsal petal pink, 10.5 × 9.5 mm, shallowly cuculate, with a shallow narrow dorsal crest. Lateral united petals bright pink with a small white spot at the base of the upper lateral petal of each lateral united pair and a deep pink spot at the base of the lower lateral petal of each pair, 19-21 mm long, with the upper petal of each pair equal in appearance compared to the lower one. Upper petal 12-13 × 8-9 mm, oval-kidney shaped; lower petal of each pair 15.5-16.5 × 12.5-13 mm, asymmetrically obovate, distally produced into 4.0-4.5 × 2.5-4.1 mm ligulate appendage. Stamens 5, alternating with the petals, connate to a ring. Ovary 5-locular, glabrous. Fruits fusiform. Seeds unknown.

Distribution.

Impatiens smetsiana is endemic to Cameroon. Only known from Tchabal Mbabo (type location; Fig. 5 ).

Habitat and ecology.

Impatiens smetsiana grows between 1900 and 2100 m, in gallery forest. Following species were collected together with the new Impatiens : Campylospermum sp., Carapa sp., Cassipourea sp., Chassalia sp., Clematis sp., Cremaspora triflora , Echinops sp., Gladiolus sp., Hypoxis sp., Moraea schimperi , Multidentia dichrophylla , Pavetta sp., Pentanisia sp., Peperomia sp., Psychotria moseskemei , Psychotria peduncularis var. peduncularis , Psychotria psychotrioides , Psychotria succulenta , Psydrax kraussioides , Rothmannia sp., and Spermacoce verticillata .

Phenology.

Impatiens smetsiana flowers in May (based on two records), fruiting occurs immediately after flowering.

Etymology.

The species epithet Impatiens smetsiana refers to the Belgian botanist, Erik F. Smets.

Preliminary IUCN conservation assessment.

Vulnerable: VU D2. The species has been collected twice in a non-protected area in the Chabal Mbabo region. Human pressure in the region (mainly cattle breeding) is significant and results in the degradation and destruction of forested areas ( Chapman 2004). Because of the restricted and fragmented distribution range of I. smetsiana , we would apply the category vulnerable under criterion D2. Human activities can make the species become critically endangered or even extinct within a rather short timeframe ( IUCN 2012, 2019).

Additional material examined.

CAMEROON - Adamawa Region • Chabal Mbabo ; 7°14 ’14” N, 12°5 ’24” E; 9 May 2009; Dessein S. & Taedoumg H. 2971; BR [BR0000034048368] .

Figures

Figure 1. A. Frontal view of I. smetsiana flower. B. Lateral view of I. smetsiana flower. C. Frontal view of I. kamerunensis subsp. kamerunensis flower. D. Frontal view of I. erecticornis flower. A-B: Dessein & Taedoumg 2971 (BR [BR 0000034048368]); C: Dessein et al. 2673 (BR [BR 0000005605668]); D: Fischer s. n. (BONN). Photos by: A-C: Steven Dessein, D: Eberhard Fischer.

Figure 4. Impatiens smetsiana. A. Habit. B. Frontal view of flower. C. Lateral view of flower. D. United lateral petals. E. Dorsal petal. F. Lateral sepals. G. Lower sepal and spur. Drawn by Antonio Fernandez from Dessein & Taedoumg 2971 (BR [BR 0000034048368]).

Figure 5. Distribution of I. smetsiana (black asterisks) in the Tchabal Mbabo region. Eq. G.: Equatorial Guinea; C. A. R.: Central African Republic; Congo Br.: Congo Brazzaville.