AMORPHOPHALLUS NIAHENSIS

PROTOLOGUE: Amorphophallus niahensis P.C.Boyce & Hett., published in Gard. Bull. Singapore 61: 264 (2010).

Amorphophallus niahensis P.C. Boyce & Hett., sp. nov. Ad Amorphophallus brachyphyllus spadix appendice echinatis, floribus masculinus nec in serialis longitudinaliter tectis, stigmate sessile subintegris; spathae anthesin feminibus reflexis, non erectis; ab Amorphophallus juliae petiolorum foliis non pallide rubro et maculatis, spathae lamina marginem nec valde revolutis differt. Type: Sarawak, Miri Division, Niah Suai District, Gunung Subis, Gua Niah N.P., along plank walk to Niah caves, 21 Aug 2002, Julaihi L et al. S 89309 (Holotypus, SAR).

DISTRIBUTION: Borneo (Sarawak): Borneo.

DISTRIBUTION NOTE: East Malaysia: Sarawak, Miri Division - known only from Niah National Park, on the Gunung Subis limestone, where it has been gathered along the plank walk to the Niah caves, outside and below the western mouth of the Great Cave, on the Madu Trail, and at Batu Niah, between about 03°48' and 03°49' N and 113°46' E.².

SPECIES DESCRIPTION:

Medium-sized, rather robust, aseasonally dormant geophytic herb to 1 m tall. Tuber depressed globose, with irregular raised areas, up to 12 cm diam., 6 cm high, surface pale brown, interior white. Leaf solitary, petiole proportionately short compared to the lamina diameter; petiole up to 60 cm long, ca 2.5 cm diameter at base, moderately turgid, cylindrical, smooth, uniform pale-green with a few obscure paler spots present in some individuals, subtended by 2-3 marcescent cataphylls, these extending ca 1/10th the length of the petiole; lamina moderately dissected, up to 1 m diam., thinly coriaceous, adaxial surface mid-green, abaxial surface paler, rachises naked except for terminal leaflets long-decurrent, narrowly canaliculate, mid-green; leaflets elliptic-lanceolate, 2-15 x 1.5-6 cm, terminal-most petiolulate, petiolule 1-2.5 cm long, narrowly canaliculate adaxially, lowermost pair of leaflets symmetrical, all others asymmetrical and obliquely inserted on petiolule, apex shortly acuminate; 3-9 pairs of primary lateral veins, these slightly impressed adaxially, abaxially slightly raised; venation forming distinct submarginal veins; interprimary veins less well-defined, secondary veins forming a weak reticulum.²

INFLORESCENCE:

Inflorescence solitary, occasionally two or rarely three together, flowering before emergence of foliage leaves but in any one colony mature plants at all stages of growth present simultaneously; peduncle and lower part of spathe encased in subfleshy cataphylls, peduncle cylindrical, up to 17 cm long, 5-6 mm diam., pale green; cataphylls several per inflorescence, elongate-ovate, 3-16 x 1-4 cm, pale greenish white, subfleshy at anthesis, soon withering and decaying, drying mid brown. Spathe broadly oblong-ovate, narrowly funnel-form, up to 9 cm long x 3 cm wide (fresh), pressed material up to 5 cm wide; spathe limb accounting for ca 1/3 or less of the spathe length, spathe mouth margins hardly recurved at anthesis and spathe limb margins planate; interior white, smooth, somewhat glossy, exterior very pale greenish white to white; lower spathe convolute and much inflated at anthesis, 2-7 cm long, interior muricate-verrucate, deep reddish purple, exterior pale greenish white, sometimes slightly pink-tinged. Spadix exceeding spathe, 9-12 cm long. Appendix up to 9 cm long, elongate-fusiform, ca 9 mm diam. (fresh), ca 4 mm diam. (dried), white, moderately echinate, producing a sharp smell of rotten fish at anthesis. Flowers unisexual; male flower zone cylindrical, up to 3 cm long, 6 mm diam., cream; stamens ca 1 mm long, ca 0.5 mm broad across, pores paired, partially fused or solitary, pollen dark yellow. Female flower zone shortly cylindrical, contiguous with the male zone, ca 4.5-7 mm x ca 7 mm diam.; pistils few, densely arranged; ovaries compressed globose, ca 1.5 x 1.5 mm, dark purple, mostly bilocular; stigma sessile, three lobed. Infructescence with up to 35 berries, pedunculate up to 22 cm long, 6 mm diam. at base, 9 mm diam. at apex, with blackish dark brown V-shaped scar from the marcescent spathe, basally with remains of the cataphylls. Fruit ellipsoid 15-16 x 8-10 mm, apex rounded, with blackish stigma remnants, when ripe deep orange, one seeded. Seeds ellipsoid, 12-14 x 7-8.2 mm wide, testa smooth, thin, yellowish green, seed copiously starchy, embryo small.²

ECOLOGY:

Grows in limestone forest, in shady places in humus-filled fissures and holes in the rock, and often on limestone emerging from swampy ground, at about 45 m.²

ETYMOLOGY:

Named for Gua Niah, the Niah caves of Sarawak, to which the species is endemic; the type was gathered beside the plank walk that carries visitors to the caves.²

NOTES:

1. Amorphophallus niahensis is most similar to Amorphophallus brachyphyllus, especially in the rather short petiole compared to the lamina diameter, but is readily distinguished by the conspicuously echinate spadix appendix, the male flowers not arranged in longitudinal lines, the concolourous deep purple pistils, and the spathe limb reflexing at female anthesis.²

2. It approaches Amorphophallus juliae in the echinate appendix, although that texture is markedly more pronounced in Amorphophallus juliae, but is readily distinguished by the pale green petiole lacking any markings rather than spotted reddish brown, and by spathe limb margins that do not or only slightly recurve at anthesis.²

3. In the wild the inflorescences very often produce two morphologically normal spathes, set at 180° to one another; the same has been seen in Amorphophallus eburneus and Amorphophallus brachyphyllus.²

4. It is one of five white-flowered species known from Sarawak, four of which - Amorphophallus eburneus, Amorphophallus brachyphyllus, Amorphophallus juliae and Amorphophallus niahensis - are limestone obligates, each confined to its own formation.²

5. It belongs to the informal Eburneus Group, held together by a set of characters no one of which is universal: irregularly bulging tubers, a corky outer skin to the tuber, turgid petioles, at least the upper male flowers vertically aligned, a fishy smell at anthesis, and large elongate fruits to about 2 cm long - barring those of Amorphophallus titanum, at 5-6 cm, the largest in the genus.²

6. ⚠ Each limestone formation carries its own species. The white-flowered limestone plants of western Sarawak are mirrored eastward by Amorphophallus julaihii on Mulu, by this species on Batu Niah and by Amorphophallus juliae on Bukit Merirai, and the pattern runs on into Sabah, where Amorphophallus tinekeae is restricted to the limestone at Gua Gomontong. The formations are geographically isolated from one another, and the species on them are closely related but distinct - presumed vicariants rather than one variable plant.²

7. Its description, alongside that of Amorphophallus juliae in the same paper, brought the number of Amorphophallus species native and endemic to Borneo to seventeen. Fifteen of those seventeen had been described in the thirty years before 2010.²

8. Material from Batu Niah has been grown at the Hortus Botanicus in Leiden, collected by Vogel under the number 970616 and held there as Hetterscheid H.AM.895.²

REFERENCES:

1. Plants of the World Online, Royal Botanic Gardens, Kew — Amorphophallus niahensis P.C.Boyce & Hett.

2. Gard. Bull. Singapore 61: 264 (2010) — protologue.

3. Alan Galloway — Amorphophallus niahensis, alangallowaybotanicals.com.

Additional photos by Pio Swiat