Psychotria deltata I.M.Turner, 2018

Turner, I. M. & Kumar, V. S., 2018, Flora of Singapore precursors, 4. A summary of scandent Psychotria (Rubiaceae) in Singapore and Peninsular Malaysia, Phytotaxa 361 (2), pp. 183-197 : 185-188

3. Psychotria deltata I.M.Turner , sp. nov. ( FIGURE 2–4 )

Type:— SINGAPORE. Reservoir woods, 28 Mar 1921, I. H. Burkill SFN 7041 (holotype SING barcode SING 0030565).

The new species is similar to P. cuspidella Miquel (1869: 209) , from Sumatra and Borneo, but differs in the leaves drying shiny above and often deltoid, with 7–9 pairs (versus 11–15) of lateral nerves, inflorescences of dense heads of more or less sessile flowers (inflorescences not capitate in P. cuspidella and with pedicellate flowers).

Scandent shrub climbing by means of adventitious roots. Twigs drying red-brown, brown or dark brown, finely longitudinally striate, generally glabrous though youngest parts occasionally with short hairs. For foliage of fertile shoots (juvenile material is more variable), leaves chartaceous to subcoriaceous, drying a uniform shade of light to dark brown, rather shiny above, main veins darker on lower surface, midrib flush to slightly sunken above in dry leaves, generally with a central longitudinal furrow, lateral nerves slightly raised to slightly sunken above, midrib and lateral nerves prominent below, glabrous above, dense covering of more or less erect brown multicellular hairs on main nerves below with a uniform tomentum of broad-based, tapering, more or less erect multicellular hairs on lower lamina which give an appearance of many minute red-brown spots on the lower lamina in older material and a slightly rough feel, lamina ovate to elliptic, 8–17 × 3–10 cm, base truncate to cuneate, generally ultimately shortly decurrent to petiole, apex shortly acuminate, notably for some specimens with more or less ovate-triangular (deltoid) leaves, lateral nerves 7–9 pairs, curving forward and looping distinctly within the margin, coarse reticulations generally visible in dry leaves. Petiole ca. 25 mm long, 1–1.5 mm wide, drying blackish, longitudinally wrinkled with very short brown hairs. Inflorescences rather small in comparison to the leafy shoot, sessile to subsessile, primary branching trichotomous, branches not exceeding 2 cm long, each bearing a dense head of more or less sessile flowers, inflorescence axes drying laterally compressed, densely short brown or red-brown hairy. No complete flowers at anthesis available—mostly after corolla has dropped. Flower pedicel plus hypanthium to c. 1 mm long, densely pale hairy, calyx tube c. 0.3 mm long, calyx lobes c. 0.7 × 0.5 mm, drying black with scattered red-brown hairs outside. Infructescence to 4 cm long, fruits more or less globose, subsessile, c. 8 mm diameter, drying strongly ribbed when immature, with brown or red-brown hairs, surmounted with persistent calyx. Pyrenes 2, flat-faced, with 3 or 4 central ridges on convex side, 6 × 5–5.5 × 2 mm.

Paratypes: —PENINSULAR MALAYSIA. Johore: Kluang, Gunung Belumut, Hutan Liput Gunung Belumut , trail to summit, alt. 91 m, 5 Apr 2011, K. Imin FRI 74681 ( K) ; Gunung Pulai, Dec 1904, H. N. Ridley 12203 ( K barcode K000777143 ). SINGAPORE. Sungei Morai, 1892, H. N. Ridley s.n. ( SING [×2] barcodes SING0030559 , SING0030557 ) ; Chan Chu Kang , Oct 1889, H. N. Ridley s.n. ( SING barcode SING0030558 ) ; Bukit Mandai, 1891, H. N. Ridley s.n. ( SING barcode SING0030560 ) ; Reservoir, 1893, H. N. Ridley 5068 ( SING barcode SING 0030553 ) ; Reservoir , 1908, H. N. Ridley s.n. ( BM) ; Seletar , 29 Mar 1889, H. N. Ridley s.n. ( BM) ; Sungei Buloh , 18 Apr 1890, Lance Corporal 2870 ( SING barcode SING0030569 ) ; s.loc., s.dat., N. Cantley s.n. ( SING [×2] barcodes SING0037369 , SING0030566 ) ; Bukit Timah , 17 Feb 1939, Z. Teruya 3132 ( SING barcode SING0037478 ) ; Seletar Reservoir, 10 Mar 1971, Mohd. Noor SR MN7 ( SING barcode SING0064261 ) .

Field notes: —Dark green leaves, pale beneath, berries juicy, white (Ridley s.n.); white berries, dark foliage ( SFN 7041); stem green, leaves pale green beneath with rusty hairs, infructescence green with hairs; fruit creamy white, sepals green ( FRI 74681)

Etymology: —The chosen epithet reflects the unusual deltoid leaves observed in some collections.

Notes: — Ridley (1923) referred a collection from Gunong Pulai, Johore, to Psychotria coriacea Korthals (1851: 242) . Korthals described P. coriacea from two collections, one each from Sumatra and Borneo. Miquel realising that the Korthals’s name was an illegitimate later homonym described Psychotria cuspidella Miquel (1869: 209) based on the same material and cited P. coriacea in synonymy. We therefore take P. cuspidella as a replacement name for P. coriacea . This makes P. melintangensis Govaerts (in Ruhsam et al. 2008: 117), a later attempt to provide a nomen novum for P. coriacea , superfluous.

A number of collections from Singapore, that had been included in P. penangensis Hooker (1880: 175) , were found to match the P. coriacea sheet from Gunong Pulai. These specimens are very distinctive for scandent Psychotria with large, leathery-looking, strongly nerved, often deltoid, leaves, with a highly characteristic tomentum on the lower lamina surface of uniformly spaced reddish hairs, the bases of which persist to give a red-spotted appearance to the lower lamina surface. No other climbing species from Peninsular Malaysia and Singapore could easily be confused with it.

In referring the Gunong Pulai collection to P. coriacea, Ridley (1923) made reference to a Beccari collection from Sumatra (P.S. 698) as the same species. This is not the case. This specimen and another (P.S. 351) have distinctive long hairs on the calyx and inflorescence axes not found in the Malayan material or P. cuspidella . The Beccari collections probably represent another undescribed species.

Psychotria cuspidella has costate leaves with a similar, though apparently less persistent, tomentum to the Malayan material, but there are many points of difference, particularly in terms of inflorescence form, which lead us to describe the plant from Singapore and Johore as a new species even in the absence of good flower material. Ridley (1923) referred a collection of his own from Semangkok Pass, Selangor, to P. cuspidella . This specimen has been misidentified and is P. malayana Jack (1820: 3) , not a scandent species. We are not aware of any correct records of P. cuspidella from the Malay Peninsula.

Psychotria grandistipula Merrill (1923: 42) from Sabah, Borneo, is another species similar to P.deltata , particularly in the form of the indumentum, but it has far more prominent stipules and a much laxer inflorescence. Merrill also noted it as a small shrub rather than a climber.

Figures

FIGURE 2. Line drawing of Psychotria deltata I.M. Turner, sp. nov. A—habit of juvenile climbing shoot. B—stipule on A. C—abaxial leaf surface from A. D—shoot bearing infructescence arising from climbing stem. E—abaxial leaf surface from D. F—example of deltoid leaf. G—flowers after corolla has dropped attached to terminal part of inflorescence axis. H—flower as in G with part of calyx excised to show interior. I—infructescence from D; indumentum only shown on right-hand branch. J—pyrene showing flat inner face. K—pyrene showing outer convex face with ridging. L—details of midrib hairs in C. M—details of hairs on lower lamina in D. N—details of hairs on inflorescence axis in I. Scale bars: dashed bar = 500 μm (L, M, N), graduated single bar = 2 mm (C, G, H, E) and 5 mm (B, J, K), double bar = 1 cm (I), graduated double bar = 5 cm (A, D, F). Material used:—A–C (SING 2010-365); D, E, I (FRI 74681); F (SFN 7041); G, H (Ridley s.n. (SING0030558)); J, K (Teruya 3132). Drawn by Andrew P. Brown.

FIGURE 3. Photograph of the type of Psychotria deltata I.M. Turner, sp. nov.

FIGURE 4. Photograph of the lower surface of a mature leaf of Psychotria deltata I.M. Turner, sp. nov. exhibiting the red-brown spotting due to the bases of hairs on the lamina surface (Ridley 5068). Scale bar = 2 mm.