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focus on...  Peperomia bangroana C.DC. rehabilitated
The African Peperomia bangroana was described by C. De Candolle in 1866. Since about half a century it is considered to be identical with Peperomia rotundifolia (L.) Kunth, a widely spread species from northern South America, Central America, the Caribbean islands and found up to South Florida. Comparative morphology of the inflorescences reveals sufficient differences to keep the two species apart. Synonymy
C. de Candole published two new, obviously closely related, Peperomia taxa in his paper “Piperaceae novae” (1866) (5): Peperomia bangroana and Peperomia mascharena. In the author’s general key to the genus (7) he distinguishes the two species based on three characters: in P. mascharena the leaves have a smaller diameter, the ovary is less immersed in the rachis and the fruits are more globose. It became obvious that these slightly quantitative differences belong to infraspecific variation. Baker & Wright (2) mentioned already the “very close alliance” of the two species and since the publication of Balle (1) P. mascharena is rightly considered as a synonym of P. bangroana.
About a decennium later Hutchinson & Dalziel (12) were the first to mention P. bangroana C. DC. as a synonym of P. rotundifolia (L.) Kunth, wide spread in northern South America, Central America, the Caribbean islands and occurring occasionally even in South Florida. Taxonomists have widely adopted this proposition (1,9,10,11,13,14,15) and for about half a century African and Malagasy herbarium specimens have been (re)labeled accordingly.
Morphology
It is true that vegetative branches of P. rotundifolia and P. bangroana can hardly be distinguished. Both species are creeping epiphytic or epilithic herbs with filiform stems and alternate, more or less orbicular, fleshy leaves. When it comes to the inflorescences there is a marked and constant difference between the American P. rotundifolia and the African P. bangroana. The overall length of the inflorescences in P. rotundifolia is up to 7 cm (herbarium specimen from Ecuador) . Knowing that the leaf diameter is about 1 cm, the proportion between inflorescence length and leaf diameter can easily be interpreted on (photographed) herbarium specimens and on drawings and paintings. A good example of the latter is a splendid image by an illustrator of the expedition of José Mutis (3). The length of the peduncle is short (less than 1 cm) in comparison with the length of the rachis. The terminal or axillar spikes often have a slightly curved form, more obvious in longer spikes.
P. bangroana on the contrary has short inflorescences (up to 1,5 cm) with peduncles being mostly as long or longer than the rachis (herbarium specimen from Kenya). This means that the rachis itself is shorter than 1 cm (sometimes as short as 2 mm). The small terminal inflorescences have a straight appearance (Malagasy specimen in habitat: notice the small inflorescence at the very left of the photo).
The observations as described were completely consistent in 123 herbarium specimens of P. bangroana (from the Comores, Cameroon, Congo, Ethiopia, Gabon, Ivory Coast, Kenya, Liberia, Madagascar, Malawi, Mozambique, Sierra Leone, South Africa, Tanzania, Togo, Zimbabwe) which have been compared to 152 specimens of P. rotundifolia (from Brazil, Colombia, Ecuador, the Greater and Smaller Antilles, the Guyanas, Peru, USA, Venezuela). DNA samples of fresh specimens of both species are stored at Ghent University to be used in a forthcoming molecular biological research.
Orthography
Since the first publication the orthography of this taxon's epithet has been rather chaotic. In 1866 (5) C. De Candolle named the species P. bangroana. The name was based obviously on the type locality (Mann 905). It concerns the Bagru river in Sierra Leone at the south border of the Moyamba district and just north of the Sherbro Island. Although Mann wrote “River Bagroo” on the label of his specimen, it is evident that the most preferable spelling should have been Peperomia bagruana. However this spelling has never been used. In later publications (6,7) the author changed the epithet to bangrooana, probably to bring it more in accordance with the spelling on the label of the type specimen. Some authors have corrected the epithet by omitting the ‘n’, changing it to bagroana (4,8,12,16). Others stuck to the originally published name (1,2) or to the alternative proposed by the author himself (9,14).
The International Code of Botanical Nomenclature states that typographical and orthographical errors have to be corrected (ICBN art. 60.1). Although the current Code provides ample rules concerning the spelling of epithets derived from personal names, there are very few directions for the spelling of geography-based epithets. As long as a name is not in conflict with the rules of the Code, the author may freely choose the specific epithet and it's spelling. Deciding to use the type locality as a basis, he can, regarding the lack of current restrictions, add and omit letters for any reason whatsoever or he might even form an anagram. No matter if a particular spelling is chosen deliberately or by accident (which is sometimes difficult to judge), once it is fixed by the first publication even the author is not free to change it.
For those reasons the taxon name has to be written as originally published: Peperomia bangroana C.DC. Alternatives as P. bangrooana, P. bagroana, P. bagruana,… have to be considered as illegitimate. This could change in the future when the ICBN would provide more restrictive rules for the spelling of geographical names used in specific epithets.
References
(1) Balle S., Flora de Congo Belge et Ruanda Urundi, Bull. Jard. Bot. Etat., Bruxelles, 16: 388. 1942.
(2) Baker J.G., Wright C.H., Flora of Tropical Africa 6(1): 154. 1913.
(3) Callejas R., red., Flora de la Real Expedición Botánica del Nuevo Reyno de Granada 1783-1816 (José Celestino Mutis) - Toma XIII Piperaceas, Iconografia Mutisiane, Ediciones Cultura Hispanica, Madrid. 1997.
(4) Dawe, Rep. Bot. Miss. Uganda Protect. 55. 1906.
(5) de Candolle C., Piperaceae novae, Journal of Botany, British & Foreign 4: 134. 1866.
(6) de Candolle C., Prodromus Systematis Naturalis Regni Vegetabilis 16(1): 404. 1869.
(7) de Candolle C., Piperacearum clavis analytica, Candollea 1: 328. 1923.
(8) Diniz M.A., Flora Zambesiaca 9(2): 29. 1997.
(9) Düll R., Die Peperomia-Arten Afrikas: 85. 1973.
(10) Edwards S, e.a., Flora of Ethiopia & Eritrea 2(1): 60-64. 2000.
(11) Friedmann F., Flore des Mascareignes - 150 : Pipéracées: 12. 1998.
(12) Hutchinson J., Dalziel J.M., Flora of Tropical West Africa 1(1) (1st ed.): 80 (19??), (2nd ed.): 83. 1954.
(13) Immelman K.I., Flora of South Africa contributions - 15: Piperaceae, Bothalia 30(1): 25-30. 2000.
(14) Nyffeler R., Rowley G.D., Illustrated handbook of succulent plants - Dicotyledons (U. Eggli, ed.). 2002.
(15) Van Jaarsveld E.J., Peperomia species of South Africa, Aloe 29(3/4): 68. 1992.
(16) Verdcourt B., Flora of tropical East Africa - Piperaceae, 1-21. 1996
Guido Mathieu - Jan 2003 [contact the author]
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