Coccinia intermedia – a new Cucurbitaceae species from West Africa

Abstract Nuclear and plastid sequences from two individuals of a suspected new species of Coccinia from West Africa were added to an available molecular phylogeny for the remaining 27 species of the genus. Phylogenetic analyses of these data indicate the new species' monophyletic status and closest relatives. Based on four fertile collections, we here describe and illustrate Coccinia intermedia Holstein. We also provide a key to the Coccinia species of West Africa and map their distributions.


Introduction
The genus Coccinia Wight et Arn. so far consisted of 27 species distributed mainly in Sub-Saharan Africa, with centers of diversity in East Africa and southern Africa (Holstein, ongoing monograph). Only four species were known from West Africa, including C. longicarpa Jongkind, C. keayana R. Fern., and C. barteri (Hook. f.) Keay, which apparently evolved during Pliocene-Pleistocene climatic oscillations (Holstein and Renner 2011). The fourth species, C. grandis (L.) Voigt, is much more widespread, occurring not only in Africa but also in South and South East Asia, and being naturalized on several Pacific islands, Australia, and in the Neotropics. During a study of the evolution and biogeography of the genus (Holstein and Renner 2011), we came across a male specimen from the northeastern Ivory Coast that in its plastid sequences differed sufficiently from all other sequenced material for us to suspect it might represent a new species. We therefore provisionally labeled it Coccinia sp. nov. We have since found three more specimens of the new species, all of them with fruits, and two with flowers, and based on their morphology as well as additional nuclear and plastid sequences, we here describe the new species C. intermedia.

Methods
We produced new sequences of the plastid rpl20-rps12 intergenic spacer (JN653687), trnS GCU -trnG UCC intergenic spacer (JN653686) and the nuclear LEAFY-like second intron (JN653688) from the female specimen A. Akoègninou et al. 2625 (WAG0278370) of the new species, following standard procedures (Holstein and Renner 2011). We added the new sequences, named "C. intermedia 2", to our published matrices and carried out maximum likelihood tree searches, using the approaches described in Holstein and Renner (2011).

Coccinia intermedia
Distribution. (Fig. 6). NE Ivory Coast, SE Ghana (likely also in the north), S Togo (likely also in the north), NW Benin. Based on the current collections, Coccinia intermedia is likely to occur in the Dahomey Gap region and the Isoberlinia woodlands of West Africa.
Ecology. Wooded grasslands (semi-humid savanna), woodlands, dry forests, and along rivers. Flowering specimens have been collected during May, August, and October, which in each site was during or shortly after the rainy season.      Plant glabrous. Leaves with small blackish glands centered towards the leaf base (Fig. 3). Nerves on lower lamina with or without white pustules. Leaf margin at maturity with colored teeth (color in living plants unknown, black when dry). Tendrils simple or bifid. Male flowers (Fig. 5) bracteate, in fewflowered racemes, female flowers 1-3 solitary/clustered ( Fig. 3 and 4). Calyx teeth erect with recurved tips (Figs 3-5)

Discussion
Coccinia intermedia is morphologically similar to the other West African species. From C. grandis, it differs most readily in the glands on the lower lamina and in its calyx teeth (erect with recurved tips in C. intermedia and spreading to reflexed in C. grandis). From C. longicarpa, it differs in its ovoid fruits (instead of long cylindrical fruits in C. longicarpa). Additionally, C. longicarpa has ebracteate racemes and much broader (> 1.5 mm at the base) erect calyx teeth, and an urn-shaped corolla. From C. keayana, it differs in having bracteate male flowers in denser racemes, a campanulate corolla and calyx teeth that are adpressed to the corolla with recurved tips, instead of spreading (in buds) to reflexed calyx teeth. Secure distinction of C. intermedia from C. barteri requires fertile material with flowers (see the key above). Ecologically, the new species is a member of White's (1983) Sudanian center of endemism and his Guinea-Congolia/Sudania regional transition zone (Fig. 6). The only species with a similar habitat as C. intermedia is C. adoensis, the most western known occurrence of which is Adamawa State (eastern Nigeria). Whether the species co-occur is not known. They could be distinguished by fruit shape (not beaked in C. intermedia, beaked in C. adoensis, although this character can vary in the latter). Additionally, C. adoensis has inflorescence peduncles that are longer than 1 cm (in its male racemes) and petioles that are often hairy.
Two DNA characters, namely base pairs 310 and 323 in the trnS GCU -trnG UCC intergenic spacer region, suggest the placement of C. intermedia as sister to a clade that we have earlier referred to as the Coccinia barteri clade (Holstein and Renner 2011). If this placement is correct, then the Coccinia species occurring in the rain or mist forests of West and Central African are monophyletic and probably evolved in situ. One of the four collections, J.B.Hall & J.M.Lock GC 46016, bears male and female flowers/fruits on the same node (Fig. 3c). The male flowers are buds, and it is not clear, whether they are fertile. Kumar and Vishveshwaraiah (1952) report a "gynodioecious form" of C. grandis in which the male flowers of the hermaphrodite (monoecious) plants are sterile. An occasional occurrence of bisexual plants in otherwise dioecious species, sometimes called "leaky dioecy" (Baker and Cox 1984), has also been observed in other Cucurbitaceae (Schaefer and Renner 2010).
However, true monoecy in C. intermedia would be surprising as none of ca. 1,500 specimens of other Coccinia species studied is bisexual (Holstein, ongoing monograph).