Codonoboea rheophytica Kiew, 2019

Kiew, Ruth & Lim, Chung-Lu, 2019, Codonoboea (Gesneriaceae) in Terengganu, Peninsular Malaysia, including three new species, PhytoKeys 131, pp. 1-26 : 6-10

Codonoboea rheophytica Kiew sp. nov. Figure 4

Diagnosis.

In its extremely narrow leaves, less than 2 cm wide and more than eight times longer than wide, it resembles the other two Peninsular Malaysian rheophytic Codonoboea species, C. densifolia and C. salicina . It shares with C. salicina the serrate leaf margin, but it differs in its leaves that have more lateral veins (33-36 pairs vs.13-18 pairs in C. salicina ) and from C. densifolia that has a leaf with an entire margin. Codonoboea rheophytica differs from both in its sessile leaves (vs. shortly petiolate, petioles 0.5-1.5 cm long), single flowers (not in inflorescences with 2-4 flowers) and longer corolla tube 30-40 × 7-12 mm (vs. 8-9 × 4.5 mm in C. densifolia and 3.3 × 3.7 mm in C. salicina ) and longer fruit 3-4.5 cm long (vs. 1.5-3 cm long). Amongst species with similar solitary flowers with a large trumpet-shaped corolla, included stamens, annular nectary ca. 1 mm tall and a large peltate stigma and sessile leaves with a serrate margin, it most resembles Codonoboea crinita that has relatively narrow leaves (13.5 –)18(– 24) × (3 –)3.5(– 4.5) cm. It differs from C. crinita in its much narrower leaves (0.8-1.3 cm wide and 14-17 times longer than wide), in its lamina that is glabrous above, except for the midrib (vs. densely hairy in C. crinita ), 33-34 pairs of lateral veins, (vs. 22 –28(– 34) pairs) and shorter fruit 2.8-4.3 cm long (vs. 5.5-8 cm long). In addition, the leaves of C. crinita are usually deep purple beneath and have a broad silver-grey band along the midrib on the upper surface. Codonoboea crinita grows on soil and is very rarely recorded as a lithophyte and, in spite of being a common and widespread species, it has never been recorded as growing on rocks in rivers or even on river banks.

Type.

Peninsular Malaysia. Terengganu, Dungun District, Rasau Kerteh Forest Reserve. 4°35.52'N, 103°17.47'E, 20 Oct 2002, Sam, Y.Y., Angan, A., Mustafa, D. FRI 47176 (holotype KEP; iso: SAN).

Description.

Rheophyte, stem erect, unbranched, woody, 12-23 cm tall, 5-6 mm diameter; apex and developing leaves densely covered in long, glossy hairs. Leaves in a dense tuft at the top of the stem, sessile; lamina narrowly lanceolate, glabrescent above, 11.5-22 × 0.8-1.3 cm, in life bullate, margin serrate, teeth ca. 1-1.5 mm long and 1.5-2 mm broad at base; midrib and veins impressed above, forming conspicuous irregular squares or polygons, midrib shortly hispid, beneath midrib and veins prominent and shortly hispid; lateral veins 33-36 parallel pairs, tertiary veins perpendicular and sending fine veins into sinus between two teeth. Flowers single from upper surface of the leaf base. Peduncle and pedicel 6-7.5 cm long, sparsely hairy; bract linear, ca. 2 mm long. Indumentum of peduncle, calyx, corolla and ovary of glandular, long- stalked hairs. Calyx 5-lobed, divided to base, 2-3 mm long, base 1 mm wide, densely pubescent; corolla trumpet-shaped, 3.2-4.5 cm long, white, minutely pubescent outside, glabrous inside, tube 3-3.5 cm long, throat yellow inside, mouth ca. 1.2 cm diameter, lobes 5, broadly rounded, upper two 0.7-1.5 × 0.6-1 cm, edge of lobes purple, upper two erect, lower three spreading, 3-3.5 mm long; stamens 2, white, glabrous, included in corolla tube, filaments ca. 10 mm long, anthers white, broadly sagittate, 2.5-3 × ca. 1.3 mm, cohering face-to-face, staminodes 2, finely linear, 2.5-3 mm long; nectary annular, 1-1.3 mm high; ovary and style densely and minutely pubescent, ovary 11-16 × ca. 1.5 mm, style 9-10 mm long, ovary and style densely hairy; stigma large, peltate 1.3-1.7 mm diameter, with large papillose cells. Fruits slender, cylindric, 2.8-4.3 cm long, ca. 1.5 mm diameter, minutely hispid, dehiscing along the upper suture.

Distribution.

Endemic in Terengganu, Dungun District, Rasau Kerteh Forest Reserve, known only from the type.

Ecology.

Rheophyte clinging onto rock surface along river in regenerated lowland dipterocarp forest at 54 m altitude.

Etymology.

Greek - rheo, pertaining to flowing water. The rheophytic habit is very unusual in Codonoboea species.

Notes.

Although Codonoboea species are common on rocks close to streams and on river banks, very few, notably C. densifolia , C. salicina and this new species, grow within the flood zone and are true rheophytes. All three have the typical habit of rheophytes, wiry stem and exceptionally narrow leaves, although C. densifolia and C. salicina are not obligate rheophytes, since they also grow on steep banks in forest.

Its flower characters place it within the Heteroboea group of species. Other species in this group are large, robust herbs with large, broad leaves quite unlike those of C. rheophytica . Molecular analysis confirms that it (labelled as Codonoboea sp. nov. 2) falls within this group ( Lim and Kiew 2014).

Figures

Figure 4. Codonoboea rheophytica Kiew, sp. nov. A habit B bracteole C flower D flower opened to show position of stamens E calyx F outer surface of calyx lobe G stamens H annular nectary I young fruit J ovary covered in glandular hairs K peltate stigma. (All from FRI 47176, drawn by Mohamad Aidil Noordin).