Kadua tahuatensis (Lorence & J. Florence) W. L.Wagner & Lorence (Syst. Bot. 30: 832, 2005).

Wagner, Warren L. & Lorence, David H., 2011, Revision of Kadua (Rubiaceae) in the Marquesas Islands, French Polynesia, with description of the new species K. lichtlei, PhytoKeys 4, pp. 125-138 : 133-134

Kadua tahuatensis (Lorence & J. Florence) W. L.Wagner & Lorence (Syst. Bot. 30: 832, 2005). Fig. 2E, F.

Hedyotis tahuatensis Lorence & J. Florence (Adansonia sér. 3, 22: 227. 2000). [Basionym]

Type.

Marquesas Islands: Tahuata: ridge between Amatea and Haaoiputeomo, south-facing slope, 2580 ft. [780 m] elevation, 19 july 1997, S. P. Perlman 16020 (Holotype: PTBG-30160!; Isotypes: BISH!, MO!,P!, PAP!, US!).

Glabrous shrubs to 2 m tall, leafy twigs 4-6 mm in diam., internodes strongly compressed, bark pale brown, smooth to striate. Leaves of a pair equal to subequal, blade elliptic to obovate-elliptic, 4.2-15 × 2-8 cm, discolorus, chartaceous to subcoriaceous, base acute to cuneate or narrowly cuneate, apex obtuse to rounded, tip sometimes abruptly short acuminate, secondary veins (5-) 6-9 pairs, weakly brochidodromous, secondary and tertiary veins prominulous on both surfaces, higher order venation obscure, margin thickened, plane; petiole stout, 2-5 × 2-3 mm, adaxially sulcate; stipules inter- and intrapetiolar, sheath cupuliform, truncate, 3 × 5-6 mm, persistent, fused with adaxial petiole surfaces and becoming thickened and horseshoe-like. Inflorescences terminal, thyrsiform cymose, 23-25-flowered, 5-6 × 4.5-6 cm (including corollas), on peduncle to 2 cm long, 1.5-2 mm in diam., flattened, primary axis 15 × 1.5-2 mm with 2 pairs of lateral branches, the basal one often branching once, lower bracts foliaceous, ovate, 1.2-2 × 1-1.5 cm, upper branch pair unbranched, ultimate branches ending in 2-3 flowers. Flowers glabrous, on stout pedicels 2-3 × 0.8-1.4, compressed, bracts scarious, ovate-trangular, 1 × 1 mm, hypanthium obconical, 3-4 × 1.5-2 mm, calyx limb campanulate, 2-3 × 4-5 mm, lobes ovate-triangular, 1.5-2 × 2-2.5 mm; corolla fleshy, pale green when fresh, lobes with dark purple margins, in bud fusiform with non-depressed apex, at anthesis salverform, tube 13-16 × 1.5-2 mm in diam. medially, lobes 4, linear-oblong, recurved, 8-10 × 1.5-2 mm, apex with a hooked appendage 1 mm long; flowers possibly dimorphic, stamens exserted for 1.5-2 mm, linear, 3-3.5 × 0.5-0.6 mm, attached 1-1.5 mm below apex of tube, apex slightly mucronulate; style included, 11-12 mm long including 2 coalescent stigmatic lobes 2.5 mm long. Fruits on stout pedicels 3-8 mm long; capsule tubinate to obovoid-turbinate, 12-20 × 6-8 mm, sub-quadrangular, 2/3 inferior, apex with short beak portion 5-6 mm long above the calyx, dehiscence at first loculicidal then septicidal, old capsules disintegrating into network of vascular bundles enclosing persistent, bisulcate endocarp. Seeds irregularly trigonous or angulate, 0.9-1.2 mm long and wide, margins with narrow wing 0.1-0.3 mm wide, testa finely reticulate.

Etymology.

The specific epithet refers to the only known island of occurrence for this species.

Distribution.

Marquesas Islands, Tahuata, known only from the island's summit crest and high southeastern slopes between 780 and 835 m elevation.

Ecology.

Occurs in wet montane forest and shrubland with species of Alsophila , Cheirodendron , Crossostylis , Hibiscus , Metrosideros , Reynoldsia , Weinmannia , and pteridophytes including Asplenium , Blechnum , Elaphoglossum , Lycopodiella and Nephrolepis ,

Conservation status.

The suitable habitat for Kadua tahuatensis on Tahuata (c. 61 km2) is indicated as an endangered environment, threatened by feral animals and invasive plants, reducing the extent of the forest. This species is extremely rare, with only five plants known from two localities. Following the criteria and categories of IUCN (2001) it is assigned a preliminary status of Critically Endangered (CR): B2a, B2b (i-iii); D: B2: total area of occupancy less than 10 km2 (ca. 5 km2). B2a, a single population known; b ( i–iii), habitat continuing decline inferred; D, population estimated to number fewer than 250 individuals.

Specimens examined.

Marquesas Islands: Tahuata: ridge between Amatea and Haaoiputeomo, southeast-facing slopes over Hanatetena village, 2740 ft. (835 m) elevation, 11 July 1997, Perlman 15954 (P, PAP, PTBG, US).

Discussion.

Morphologically Kadua tahuatensis closely resembles Kadua nukuhivensis , and molecular evidence places these two as sister species in the same clade as Kadua rapensis F. Br. and Kadua romanzoffiensis Cham. & Schltdl. within the larger clade of Hawaiian and French Polynesian species ( Motley 2003).

Figures

Figure 2. Seeds of three Marquesan Kadua species, whole seed and surface detail A, B Kadua lichtlei, Wood 10514 (PTBG) C, D Kadua nukuhivensis C Perlman 15029 (PTBG) D Perlman 15054 (PTBG) E, F Kadua tahuatensis Perlman 16020 (PTBG).