Timonius tambuyukonensis J.Chen, 2014

Chen, Junhao, Wong, Khoon Meng, Ent, Antony Van Der & Tan, Hugh T. W., 2014, Nine new species of Timonius (Rubiaceae) from Kinabalu Park, Borneo, Phytotaxa 181 (3), pp. 138-150 : 148-149

Timonius tambuyukonensis J.Chen , sp. nov. ( Figs. 3D, 3E, 3G )

Similar to Timonius clementis Merrill (1917:244) ( Fig. 3F ), but differing by the narrowly triangular to lanceolate (vs. broadly ovate) stipules, smaller leaf blades (5.8–9 × 3–5 cm vs. 10.2–17.8 × 4.1–10 cm), strongly revolute (vs. plane) leaf margins, smaller peduncular bracts in female inflorescence (2–2.5 × 1–1.5 mm vs. 4–5.5 × 2–2.5 mm), and smaller fruits (5.5–8 mm vs. 9–13 mm in diam.).

Type: — BORNEO. Sabah: Kinabalu Park, Mount Tambuyukon, between Camp III to summit, 5 October 1990 (♀ plant), Jamili et al. SNP 4799 (holotype SAN; isotype SNP) .

Treelet ca. 2 m tall; trunk dbh and bark unknown. Stipules narrowly triangular to lanceolate, plane, not 2-ridged, imbricate. Leaves opposite; petioles 3–8 mm long, 1–2 mm in diam.; blades elliptic, 5.8–9 × 3–5 cm, base cuneate, apex cuspidate, margins strongly revolute, coriaceous, lower surface subglabrous on the midrib and secondary veins, glabrous on the lamina, upper surface plane to slightly bullate; secondary veins 7–10 on each side of the midrib, 3–14 mm apart from each other; tertiary veins not prominent on lower surface. Inflorescences: female plants with a solitary flower per inflorescence, peduncles 0.6–1 cm long, peduncular bracts triangular, 2–2.5 × 1–1.5 mm; male plants with 2–3 flowers per inflorescence, peduncles ca. 0.5 cm long. Calyx lobes in female flowers 4, broad-triangular (length about the same as the basal width), 1–1.5 mm long, sparsely pubescent outside; in male flowers 4, broad-triangular, ca. 2 mm long, sparsely pubescent outside. Corolla in female flowers with mature tube length unknown, ca. 1.5 mm in diam., densely pubescent outside, lobes 4, lanceolate, 3–4 mm long, densely pubescent outside; in male flowers with tube ca. 7 mm long, ca. 1.5 mm in diam., densely pubescent outside, lobes 4, lanceolate, 3.5–4 mm long, densely pubescent outside. Fruits globose to ellipsoid, 5.5–8 mm in diam., glabrous; peduncles 1.6–2.1 cm long, glabrous; persistent calyx lobes broad-triangular, 1–2.5 mm long.

Etymology: —The specific epithet refers to Mount Tambuyukon, where this species is probably endemic.

Distribution: —Endemic to Kinabalu Park (possibly restricted to Mount Tambuyukon).

Habitat: —Lower montane forest, on ultramafic substrates.

Proposed conservation status: —The species is here classified as ‘Near Threatened according to IUCN (2001) categories. Although this ultramafic endemic species is restricted to a small area on Mount Tambuyukon, there is no evidence of decline or fluctuations in EOO, AOO, number of locations, and number of mature individuals. Furthermore, the known populations seem securely conserved within the boundaries of Kinabalu Park. Nevertheless, its restricted distribution may render the known populations particularly susceptible to disturbances, such as forest fires associated with droughts and climate change.

Additional specimens examined (paratypes): — BORNEO. Sabah: Kinabalu Park, Mount Tambuyukon, 13 April 2011 (♀ plant), Van der Ent et al. SNP 24479 ( SNP), 18 March 1991 (♀ plant), Jamili et al. SNP 4078 ( SAN, SNP); Mount Tambuyukon , sub-station Monggis , 1400 m, 19 August 2007 (♂ plant), Yabainus & Barkman SNP 14310 ( SNP); Mount Tambuyukon , trail from Rajah Camp to the top of Mount Tambuyukon , 7 October 2009 (♀ plant), Rimi et al. SNP 17555 ( SNP); Mount Tambuyukon , trail to summit from Kampung Monggis, 11 March 1993 (♀ plant), Jamili et al. SNP 5560 ( SAN) .

Figures

FIGURE 3. A. Solitary fruit of Timonius kinabaluensis, Amin SAN 115990 (SAN). B. Solitary fruits of T. ophioliticus, Leopold SAN 81740 (L). C. Male inflorescences of T. ophioliticus, Muin SAN 31658 (SING). D. Strongly recurved leaf margins of T. tambuyukonensis, Van der Ent et al. SNP 24479 (SNP). E. Solitary female flowers of T. tambuyukonensis, Van der Ent et al. SNP 24479 (SNP). F. Stipules and female inflorescence of T. clementis, Wong & Kambira WKM 2410 (L). G. Solitary fruit of T. tambuyukonensis, Van der Ent et al. SNP 24479 (SNP). H. Solitary fruit of T. stenolobus, Clemens & Clemens 40171 (L). Scale bars: 1 cm. [Photos:A and C, J. Chen; B, F, and H, K.M. Wong; D, E, and G, A. van der Ent]