Timonius megalocalyx P.K.Hoo, 2023

Hoo, Pui Kiat, Sugumaran, Manickam & Wong, Khoon Meng, 2023, Two new species of Timonius (Rubiaceae: Guettardeae) from the Malay Peninsula, Phytotaxa 599 (3), pp. 171-182 : 175-177

Timonius megalocalyx P.K.Hoo , sp. nov. ( Fig. 4 )

A species distinctive in a group characterised by sub-scalariform tertiary leaf venation with fine reticulations in between, conspicuous ovate calyx lobes, large fruits up to 18 mm diameter, and dense internal fruit matrix. Most resembling Timonius wrayi except in having sparsely short-hairy (vs glabrous) lower leaf lamina surfaces, densely hairy (vs sparsely hairy to subglabrous) stipule outer surfaces as well as calyx lobes that are 5–8 mm long (vs 2–3 mm long) and reflexed (vs erect) in fruits.

Type: — Peninsular Malaysia, Johor, Labis F. R., ‘ Buaya Sangkut’ Falls , 28 May 1986, Wong FRI 32472 (holotype KEP [barcode no. 164708]; isotypes KEP [barcode no. 164703], L [barcode no. 2964779], SING – ♀ Fru) .

Timonius wrayi auct. non King & Gamble , J. Asiat. Soc. Bengal, Pt. 2, Nat. Hist. 73 (1904) 54: sensu Ridley, Fl. Malay Penins. 2 (1923) 115, pro parte; Wong, Kew Bull. 43 (1988) 512, pro parte, quoad Wong FRI 32472 et specim. al. (indicated by * in the listing below); Wong et al., Fl. Singapore 13 (2019) 317.

Tree recorded as up to 21 m tall, 20 cm diameter. Bark grey-brown, smooth. Young twigs with sparse to dense appressed brown hairs (the surface visible among hairs or mostly obscured by hairs). Stipules triangular, imbricate, outer surface completely ascending brown hairy including along margins. Leaves: petioles 10–45 mm long, 2–2.5 mm diameter, sparsely to densely ascending brown hairy, glabrescent; blades drying discolorous (dark brown on upper surface, brown on lower surfaces); elliptic to obovate, 6.5–16 × 2.5–9 cm, length:width ratio 1.7–3.1, coriaceous; lower lamina surface smooth, sparsely appressed silvery short-hairy, not silky to the touch, midrib and secondary veins drying brown to black (green to purplish when fresh), sparsely to densely ascending brown hairy; upper surface glabrous except for sparse ascending brown hairs on veins in young leaves; base cuneate, margin plane, apex acute to cuspidate; secondary veins 6–9 pairs, fading towards leaf margin; tertiary veins on lower surface sub-scalariform with fine reticulations in between, immersed in the lamina, clearly visible. Pistillate inflorescence with a solitary flower, peduncles 0.3–0.5 cm long, ca. 2 mm diameter, completely ascending brown velvety, bracts narrowly triangular, entire, 8–9 × 2–4 mm, completely ascending brown velvety; hypanthium and calyx completely ascending brown velvety; corolla not seen. Staminate inflorescences with 3–10 flowers, branching dichasial, peduncles 0.5–2 cm long, 2–3 mm diameter, completely ascending brown velvety, successive side branches hardly developed (flowers often appearing tightly bunched together), bracts narrowly triangular, entire, 5–7 × 3–3.5 mm, completely ascending brown velvety; hypanthium 1.5–2 mm long, 1–1.5 mm diameter, inconspicuously lobed, completely ascending brown velvety; calyx tubes 1.5–2.5 mm long, 2.5–3 mm diameter, completely ascending brown velvety, lobes 4, ovate, 3–5.5 mm long, 2–3 mm wide, completely ascending brown velvety on both sides; corolla tubes 8–11 mm long, ca. 1.5 mm diameter, completely ascending silvery hairy, lobes 4, ovate, 3.5–4.5 mm long, 2–2.5 mm wide, completely ascending yellow hairy. Infructescence with a solitary fruit, peduncles 0.5–1.5 cm long, ca. 2 mm diameter, completely ascending brown velvety; fruits sub-globose to ellipsoid, 15–20 mm long, 11–13 mm diameter, completely ascending brown velvety, smooth or with 4 indistinct lobes, internal matrix dense with inconspicuous air spaces; persistent calyx tube at fruit apex absent; persistent calyx lobes 4, ovate, 5–8 mm long, 3–4 mm wide, completely ascending brown velvety on both sides, reflexed; pyrenes 9–13 per fruit, ellipsoid, with walls 0.5–2.5 mm thick.

Etymology: —The specific epithet refers to the large calyx lobes in both flowers and fruits.

Habitat: —Primary lowland mixed dipterocarp forest on slopes and ridges to 650 m elevation.

Distribution: —Endemic to Peninsular Malaysia and Singapore. Known from Peninsular Malaysia on the eastern state (Terengganu) to south central and southern states (Pahang and Johor) and from Singapore on the eastern part (Changi and Sungei Loyang).

Preliminary conservation status: — Timonius megalocalyx is assessed as Vulnerable (VU B2ab(i,ii,iii,iv)). The estimated AOO and EOO are 56 km 2 and 42,608 km 2, respectively with ten locations. Due to land-use change to urban development (e.g. in Singapore) and oil palm plantation in East Johor, an estimated 27% of AOO, 8% of EOO, area of habitat and number of locations have declined. Furthermore, the species may be particularly sensitive to habitat disturbance since it prefers relatively undisturbed environment based on our field observations. The population in Singapore is presumably extinct ( Wong et al. 2019).

Additional specimens examined: — PENINSULAR MALAYSIA. Johor: Kluang District, Rengam F.R., Gunung Lambak Microwave Station , 19 September 1970, Suppiah FRI 17772 * ( KEP, SING – ♀ Fru). Kota Tinggi District, Sungai Kayu Ara , 11 May 1935, Corner SFN 29326 * ( SING – ♀ Fru). Mersing District, Jemaluang , 2 May 1991, Teo & Remy KL 4036 ( KEP – ♂ Fl); Penyabong, May 1908, Foxworthy KEP 1183 * ( SING – ♂ Fl), Foxworthy KEP 1173 * ( SING – ♀ Fru); Sekakap Mersing, 5 May 1921, Watson KEP 5824 * ( SING – ♂ Fl). Pahang: Jerantut District, Taman Negara , riverbank of Sungai Tahan , 22 April 1975, Chan FRI 23816 * ( KEP, SING – ♂ Fl). Rompin District, Aur F.R ., Compt. 34, 10 May 1967, Whitmore FRI 3637 * ( KEP, SING – ♂ Fl); Lesong F.R. , 4 May 1982, Vethevelu FRI 29667 * ( KEP, SING – ♂ Fl); Ulu Sungai Anak Endau, 1300 ft. [390 m], 5 April 1968, Cockburn FRI 8143 * ( KEP, SING – ♂ Fl); Termeloh District, Gunung Benom Game Reserve , Ulu Krau, 2000 ft. [600 m], 19 April 1967, Rahiem KEP 97806 * ( KEP, SING – ♂ Fl). Terengganu: Besut District , Jabi , jungle path to Gunung Tebu, ca. 2000 ft. [600 m], 1 June 1974, Md. Shah, Ahmad & Mahmud MS 3297 * ( KEP, KLU, SING – ♀ Fru); Ulu Sungai Kemia, 1800 ft. [550 m], 26 April 1968, Cockburn FRI 8203 * ( KEP, SING – ♀ Fru). Dungun District, 500 m, 2 May 1968, Soepadmo KLU 9145 * ( KLU – ♂ Fl); Bukit Bauk F.R. , 20 November 1978, Chan FRI 25172 * ( KEP – ♂ Fl), 362 m, 4.7°N 103.405°E, 27 April 2016, Syazwani et al. FRI 83781 ( KEP – ♂ Fl), Compt. 10 , 18 June 1967, Kochummen FRI 2368 * ( KEP – ♀ Fru), trail to TM station , 140 m, 4.706°N 103.393°E, 5 June 2022, Hoo & Vuthy HPK 86 ( KLU – ♂ Fl). Hulu Terengganu District, Tembat F.R. , 394 m, 5.2°N 102.574°E, 3 June 2010, Wilkie, Ong & Norazmi FRI 72029 ( KEP, SING – ♂ Fl). Setiu District, Sungai Pelong , 9 April 1971, Suppiah FRI 14863 * ( KEP, SING – ♂ Fl). SINGAPORE. Changi, 1894, Ridley s.n.* ( SING – ♂ Fl); Sungei Loyang, 1894, Ridley 6699* ( SING – ♂ Fl) .

Figures

FIGURE 4. Timonius megalocalyx. A. Habit, leafy branch with fruits. B. Young twig showing stipules at shoot apex. C. Close-up of lower leaf surface. D. Stipules in transverse section showing aestivation. E. Staminate inflorescence. F. Staminate corolla bud, in transverse section showing imbricate aestivation. G. Fruit. H. Fruit, in transverse section.A–C, G–H: Wong FRI 32472; D: Hoo HPK 86; E–F: Chan FRI 23816. Drawing by Violette Chye Lay Choon.