A new genus and species, Stenosepala hirsuta, of the Alibertia group (Gardenieae, Rubiaceae), from northern Colombia and southern Panama, is described and illustrated. The new taxon is distinguished from closely related genera by its needle-like calyx lobes, persistent triangular and aristate stipules, large thyrses in male individuals, and its very hirsute ovary in female flowers. In a recent phylogenetic study of the pantropical tribe Gardenieae, I included a previously undescribed taxon from northern Colombia and southern Panama (Persson, 2000 a). Just like the genera in Gardenieae, the new taxon is characterized by having indehiscent fruits with numerous seeds in a placental pulp, and corollas with contorted aestivation. This phylogenetic study using chloroplast DNA sequences from the rps16 intron and trnL-F intergenic spacer clearly indicated that Stenosepala hirsuta (under the name species nova) is a member of the neotropical Alibertia group. However, due to poor resolution inside the Alibertia group, the analyses did not reveal the sister group to Stenosepala. Stenosepala shares several characters with the members of the Alibertia group that support its inclusion in this group, such as dioecy and heteromerous flowers (male and female flowers of different merosity), as well as pollen grains shed in monads. In addition, like the majority of the species in this group, the female inflorescence consists of a solitary flower, whereas the male inflorescence is multiflowered. In subsequent analyses of the Alibertia group using faster evolving ITS and 5S sequences of the nuclear ribosomal DNA, the general resolution and support for several clades improved (Persson, 2000 b). However, Stenosepala appeared either as the sister group to the rest of the genera of the Alibertia group or on a basal polytomy together with Stachyarrhena, a clade of two Genipa species, and a large clade comprising Alibertia, Borojoa, Duroia, and Amaioua species. Hence, the closest relative of Stenosepala hirsuta remains unresolved. Stenosepala is easily distinguished from other genera in the Alibertia group by its combination of narrow calyx lobes, persistent aristate stipules, a large thyrse in male individuals, and a very hirsute ovary in female flowers. The narrow calyx lobes and the hirsute young branchlets and ovary give Stenosepala a superficial resemblance to Duroia hirsuta (Poeppig & Endlicher) K. Schumann. However, D. hirsuta differs in many characters of which calyptrate, circumscissile stipules, which are shed as the shoot elongates, and the swollen, hollow branchlets, which house ants, are the most striking ones. Aristate stipules, narrow calyx lobes, and a large thyrse in male individiuals, as well as dioecy, also occur in Randia (Burger & Taylor, 1993), a non-Alibertia group member of Gardenieae. However, Randia is readily distinguished from Stenosepala, and the rest of the genera in the Alibertia group, by pollen grains shed in tetrads, a unilocular ovary with parietal placentas, the presence of thorns, and homomerous flowers. Stenosepala hirsuta C. Persson, gen. et sp. nov. TYPE: Colombia. Antioquia: Mpio. Tarazd, corregimiento El Doce, Hacienda Las Mercedes, 7?28'N, 75'18'W, 150 m, 12 Sep. 1998, F Alzate, R. Callejas & J. Benavides 560 (holotype, HUA; isotypes, COL, GB, NY). Figure 1. Frutex, arbuscula vel arbor, dioica, ad 10 m alta, ramis juvenibus sparse hirtellis vel hirsutis. Stipulae triangulares, aristatae, persistentes. Petiolus glaber vel hirsutus, ad 18 mm longus. Lamina in sicco papyracea, elliptica vel anguste obovata, basi anguste cuneato, apice acuminato, 19.5-29 x 8.5-11 cm. Flores masculini in thyrso, pedunculo hirsuto ad 10 mm longo. Pedicelli hirsuti 3-20 mm longi, bracteolis acicularibus. Calyx cupulatus 2.2 x 1.5 mm, lobis acicularibus. Corolla hypocrateriformis membranacea, alba, tubo ad 23 mm longo, extus sparse hirsuto, lobis sex glabris linearibus ad 21 x 2 mm. Flos femineus solitarius, pedunculo ad 2 mm longo. Calyx cupularis, dense hirsutus, lobis 8-9 acicularibus hirsutis 812 mm longis. Corolla hypocrateriformis membranacea eburnea, tubo ad 17 mm longo, extus hirsuto, intus glabro, lobis 21 x 3-4 mm, glabris. Ovarium 3-4-loculare, ovulis in quoque loculo 15-25. Fructus ? sphaericus 2.5--4.5 X 2.5-5 cm, aliquanto porcatus in sicco, indehiscens. Calycis lobi in fructu persistentes, sed saepe effracti. Hoc genus novus a generibus affinibus neotropicis, stipulis triangularibus aristatis persistentibus, calycis lobis acicularibus atque floribus masculinis in thyrso grandi, bene differt. NOVON 10: 403-406. 2000. This content downloaded from 40.77.167.61 on Thu, 28 Apr 2016 06:13:28 UTC All use subject to http://about.jstor.org/terms