Taxonomic revision of the tribe Hymenodictyeae (Rubiaceae, Cinchonoideae)

Abstract

The palaeotropical tribe Hymenodictyeae Razafim. & B. Bremer, belonging to the otherwise predominantly Neotropical subfamily Cinchonoideae s.s. (coffee family or Rubiaceae), is revised here. The tribe as presently circumscribed contains two genera, Hymenodictyon Wall. and Paracorynanthe Capuron ex J.-F. Leroy, and is distinct from the other Cinchonoideae tribes with capsular fruits in having stipules bearing large, deciduous colleters on the margins, valvate corolla aestivation, and lenticellate capsular fruits that contain elongate, bilaterally flattened, and accrescent placentae. We recognize 22 Hymenodictyon species, including four new species ( H. antakaranensis sp. nov. , H. epiphyticum sp. nov. , H. madagascaricum sp. nov. , and H. tsingy sp. nov. ), and the two described species of Paracorynanthe . Hymenodictyon is distinguished from its sister genus, Paracorynanthe , by simple or compound spicate, racemose or thyrsoid inflorescences and corolla lobes without any appendages, rather than compound umbelliform inflorescences and corolla lobes prolonged by ciliate appendages. A full taxonomic treatment, keys, and distribution maps of all recognized Hymenodictyon and Paracorynanthe species are provided. Five lectotypes and one neotype are designated. Finally, six Hymenodictyon species are illustrated for the first time.

Amphistemon and Thamnoldenlandia, two new genera of Rubiaceae (Spermacoceae) endemic to Madagascar

“…(De Block, Degreef & Robbrecht, 2002), Gyrostipula J.‐F.Leroy (Emanuelsson & Razafimandimbison, 2007), Hymenodictyon Wall. with Paracorynanthe Capuron (Razafimandimbison & Bremer, 2006), Ixora L. (De Block, in press), Lathreaocarpa Bremek. (Groeninckx et al ., 2009b), Mantalania Capuron ex J.‐F.Leroy (De Block & Davis, 2006), Paederia L. (Puff, 1991), Paracephaelis Baill.…”

Iridoids from Hymenodictyon floribundum

“…10 The 1 H NMR spectrum of compound (1) ( [12][13][14][15] (gardenamide class), and some were obtained as metabolites produced by human 16 and rat intestinal bacteria. 17 Comparison with the published data of known iridoid alkaloids, such as (6) (Figure 1), and hemiacetal-secoiridoids 11,18 like (7) ( Figure 1) and compound (1) 11,18 showed that (1) it was neither a hemiacetal nor a nitrogen-containing iridoid (N-2) but that it was compatible with a C-1(N)O-2 substitution. This was also supported by the presence of the 1 H-1 H COSY correlation between H-1/NH, rather than the H-1/NH, H-3/NH correlations expected in the iridoid alkaloids, 17 and by UV and IR data indicating the presence of the chromophore -OOCC=CHO.…”

“…Of these, 11 are endemic to Madagascar, 4 to Asia and 7 to Tropical Africa. 1 Hymenodictyon floribundum B.L. Rob.…”

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“…Within the tribe Hymenodictyoneae, Hymenodictyon is easily recognized by the thick, non-plated (i.e. more or less smooth) bark, and the ellipsoid, capsular fruit (Razafimandimbison & Bremer 2006).…”