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| Impatiens smetsiana S.B.Janssens, Taedoumg & Dessein, in Janssens, Taedoumg & Dessein, 2022. |
Abstract
Background and aims – The genus Impatiens is known for its enormous convergent phenotypic adaptation, with similar floral traits having independently evolved in distantly related lineages. The large functional convergence of Impatiens flowers causes a high degree of homoplasy for several phenotypic characters resulting in increased difficulties to distinguish between species with a similar morphology that are only distantly related, however. As a result, some species remain under the radar, as they are confused with other well-known species. This was the case for a new Impatiens species from the Tchabal Mbabo Mountains in Cameroon – Impatiens smetsiana – that was initially mistaken for the morphologically similar species I. erecticornis, an endemic from Central East Africa.
Material and methods – A combined molecular-morphological approach was applied in which phylogenetics (ITS, ImpDEF1, and ImpDEF2), biogeography, and age estimation analyses were combined with morphological data on floral and vegetative structures.
Key results – In this study, we demonstrate the close affinity of the newly collected material with a group of Equatorial West African species, including I. filicornu, I. nzabiana, I. oumina, and I. kamerunensis. The present finding represents a clear case of convergent evolution in which two distantly related taxa independently converged on practically the same flower morphology.
Conclusion – Within Impatiens, several examples of floral homoplasy have been observed yet not in such a clear way. The convergent evolution of the flowers of I. smetsiana and I. erecticornis is undoubtedly closely correlated with an adaptation to a similar pollination syndrome.
Keywords: Adamawa, biogeography, Cameroon, convergent evolution, diversification, Impatiens, speciation
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| Impatiens smetsiana S.B.Janssens, Taedoumg & Dessein, 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 [BR0000034048368]). |
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| A. Frontal view of Impatiens smetsiana flower. B. Lateral view of I. smetsianaflower. C. Frontal view of I. kamerunensis subsp. kamerunensis flower. D. Frontal view of I. erecticornis flower. A–B: Dessein & Taedoumg 2971 (BR [BR0000034048368]); C: Dessein et al. 2673 (BR [BR0000005605668]); D: Fischer s.n. (BONN). Photos by: A–C: Steven Dessein, D: Eberhard Fischer. |
Impatiens smetsiana S.B.Janssens, Taedoumg & Dessein, sp. nov.
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.
Etymology: The species epithet smetsiana refers to the Belgian botanist, Erik F. Smets.
Steven B. Janssens, Hermann Taedoumg and Steven Dessein. 2022. Impatiens smetsiana, Another Example of Convergent Evolution of Flower Morphology in Impatiens. Plant Ecology and Evolution. 155(2): 248-260. DOI: 10.5091/plecevo.89701