Euphorbiaceae)

Plant Ecology and Evolution 151 (3): 352–379, 2018 https://doi.org/10.5091/plecevo.2018.1445 REGULAR PAPER Revision of the African genus Crotonogyne (Euphorbiaceae) Frans J. Breteler Grintweg 303, NL 6704 AR Wageningen, The Netherlands (formerly Herbarium Vadense, Wageningen) E-mail: [email protected] Background and aims – The African genus Crotonogyne is revised for the first time since 1912. Identification of new material collected since proved to be very difficult. The revision serves also as a basis for the treatment of the genus in the Flore du Gabon. Methods – Normal practices of herbarium taxonomy have been applied to study the relevant herbarium material available, mainly from BM, BR, BRLU, HBG, K, MA, P, and WAG. The relevant collecting data are stored in the Naturalis Biodiversity Center, Leiden, Section Botany. MAPMAKER was used to produce the distribution maps. Key results – Eleven species are recognised including two new species: Crotonogyne micrantha from Cameroon and C. neglecta from Nigeria, Cameroon, and Equatorial Guinea (Rio Muni). Crotonogyne manniana subsp. congolensis is raised to specific rank. All species, except for C. congolensis with one collection from Angola, are confined tot the Guineo-Congolian region. A full taxonomic treatment with key to the species is given. Male and female flowers of most species are depicted. The distributions of the species are mapped. The flowers are unisexual, but it is not clear whether the species are monoecious or dioecious. Crotonogyne poggei and C. impedita are neotypified and C. angustifolia, C. gabunensis, C. lasiocarpa, C. ledermanniana, C. manniana, C. preussii, C. strigosa, and C. zenkeri are lectotypified. Key words – Crotonogyne, Euphorbiaceae, new species, tropical Africa, Guineo-Congolian Region, taxonomy. INTRODUCTION (1994) placed Crotonogyne in the subfamily Acalyphoideae, tribe Aleuritideae, subtribe Crotonogyninae Webster (1975), The African genus Crotonogyne was described in 1864 by together with two other African genera Cyrtogone and Man- Müller Argoviensis with one species, C. manniana Müll. niophyton. Radcliffe-Smith (2001) followed Webster (1994) Arg. from the island Bioko of Equatorial Guinea. Baillon in his classification of the genus Crotonogyne. (1891) described the second species, a rheophyte from Ga- bon, but placed it in Manniophyton. Pax (1894, 1897, 1899) The genus has not been revised on an African scale since and Prain (1911, 1912a, 1912b, 1912c) published most of the 1912 when it was treated for the Flora of tropical Africa by 23 specific names available (Govaerts et al. 2000). Pax & Prain (1912c) and in the same year in Das Pflanzenreich by Hoffmann (1912) classified it in the subfamily Crotonoideae, Pax & Hoffmann (1912). Identification of new material col- tribe Chrozophoreae in a group of genera with an irregular lected since proved to be very difficult due to incorrect or 2–3-lobed male calyx. In the same publication they subdi- incomplete delimitation of the species. A complete revision is vided Crotonogyne into Crotonogyne s. str. with free male therefore undertaken, also as a basis for the treatment of the petals, counting two species, the type species C. manniana genus in the Flore du Gabon. and C. preussii Pax, and a separate genus Neomanniophy- ton with male petals fused at the base for the remaining 12 MATERIAL AND METHODS species. Because Crotonogyne manniana has in fact fused male petals, Prain (1913) correctly observed that Neoman- Classical methods of herbarium taxonomy were followed. niophyton is superfluous. For Crotonogyne preussii, the sec- This study is based on all Crotonogyne herbarium speci- ond species of Crotonogyne s. str., he suggested, eventually, mens from the herbaria of BM, BR, BRLU, HBG, K, MA, P, a sectional position as an adequate recognition. Pax (1914) and WAG. The search for lost type material from B (Berlin) however, reduced Neomanniophyton to a subgenus of Croto- was done at the herbaria of BR, HBG, K, and P, and was nogyne and wrongly transferred C. manniana to it. Webster most succesful at HBG. The selection of a neotype for two All rights reserved. © 2018 Meise Botanic Garden and Royal Botanical Society of Belgium ISSN: 2032-3913 (print) – 2032-3921 (online) Breteler, Revision of Crotonogyne (Euphorbiaceae) names has been done with respect to characters given in the tion male and female shrubs, but those of Mc Pherson 15551 protologues and origin of their types. The Index Herbario- of the same species state monoecious, as Letouzey 10344 for rum (Thiers continuously updated) is followed as regards C. zenkeri. Of the latter species Bos 5732 notes “shrub not the herbarium acronyms. Specimens cited but not seen are strictly dioecious, but producing usually one sex at the time” marked with an asterisk. The relevant data of all specimens and of Bos 4364 of the same species, “dioecious, but also are stored at the Botany Section of Naturalis, Biodiversity bisexual plants, flowers always on different inflorescences”. Center, Leiden. All illustrations (figs 1–23) are based on her- The WAG specimen of this last collection shows a branchlet barium material. Morphological illustrations were prepared with a female inflorescence and also an impoverished male from the specimens mentioned in the captions. MAPMAK- one. Prain (1912c) in his description of C. zenkeri noted that ER was used to produce the distribution maps from geolocal- “casually male and female racemes on the same branch, and ized specimens. casually a solitary female flower at base of the male raceme”. And about the male flowers in spikelets arranged in separate RESULTS glomerules he stated that “the rarely simply glomerulate ar- rangement of male flowers may be provided with a solitary Morphology central female flower accompanying each glomerule”. The The habit of Crotonogyne species is a shrub or small tree latter situation has not been observed in the material inves- with lepidote or stellate indumentum (fig. 1A–H), in some tigated for this revision. In conclusion it may be stated that species (e.g. C poggei) mixed with simple strigose or hispid Crotonogyne individuals may be bisexual or unisexual, or hairs (fig. 1I–K). The stipules are usually not early shed, but are producing only one sex at the time, or at least on different they offer no distinctive characters. The alternate leaves have branches. The bisexual status is most likely for C. neglecta two, sometimes three or even four, distinct glands at the base and C. zenkeri individuals. of the lamina on the upper surface next to the midrib (figs The flowers of Crotonogyne are basically mostly 5-mer- 7F, 11A & 13C), though they are often missing in C. parvi- ous, although mixtures of 4-and 5-merous flowers do occur folia. The glands on the lower leaf surface are arranged in a in some species (e.g. C. gabunensis) in the same specimen. simular pattern for all species (see figs 7A & 13B), except for C. micrantha has only 4-merous flowers, but this species C. parvifolia where this pattern does not occur or is obscure. is only known from two collections. The calyx of the male In many species, C. caterviflora and C. parvifolia excepted, flowers opens by splitting into 2–3(–5) parts. The male petals, some leaf laminas are very narrowly attenuate at their base 4–6(–7) in number, are free or united, only in their basal part as to form a so-called false or pseudopetiole (e.g. fig. 7C) or ± completely so in C. zenkeri (fig. 23B). In C. poggei the that may reach a length of 5.5 cm in C. micrantha. Leaves petals are as a rule united at their base, but free petals have with such a pseudopetiole occur mixed with leaves without a few times been observed. The extrastaminal disc consists a false petiole, i.e with true petiole only. The inflorescences of 5–8, usually free lobes. The number of stamens varies be- are slender, ± erect, scarcely branched, and the male ones tween 6 in C. preussii and 28 in C. giorgii. They may be ± may reach a length of more than 1 m. The male flowers are free or more or less united into a short androphore as in C. arranged in distant glomerule-like entities (e.g. fig. 7B) or poggei, C. preussii and C. zenkeri (e.g. fig. 19A, 21A, 23A). in basally branched, densely bracteate spikelets (fig. 13D), There is no pistillode. The female flowers have a long pedi- which are supported by a biglandular (rarely with up to 3 or cel. The sepals, 4–5 in number, are usually united at base and 4 glands) bracts (e.g. figs 1L & M, 7D, 13D). These glands may be provided by a single large gland in the sinus between are missing in C. caterviflora. The female inflorescence is, the lobes (fig. 5A) or more or less, usually smaller, on the as a rule, shorter than the corresponding male one. The fe- margin (fig. 23D). Once, in C. poggei, shortly stalked glands male flowers are single or a few together, sometimes more or have been observed. The female sepals of C. micrantha are ± less crowded towards the top of the inflorescence. They are free and biglandular at base. The petal number in the female also, C. caterviflora again excepted, supported by a glandu- flowers varies between 4 and 6, they are always free. The fe- lar bract as in the male inflorescences. male disc is annular to more or less cupular. The three styles The question whether the unisexual flowers of Croto- are short, they are unforked in C. manniana (fig. 11G), but at nogyne are monoecious or dioecious remains unanswered, least once to several times forked in the remaining species, at least for most species. Pax & Hoffmann (1912, 1931) producing few to many stigmas. The fruit is a 3-seeded cap- and Pax (1921) described the genus as dioecious and Prain sule.

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