Iguanura polymorpha Beccari (1889: 189)

Henderson, Andrew, 2025, A revision of Iguanura (Arecaceae, Arecoideae, Areceae), Phytotaxa 690 (2), pp. 135-188 : 174-176

25. Iguanura polymorpha Beccari (1889: 189) . Type:— MALAYSIA. District of Perak in the Malay Peninsula, no date, B. Scortechini 318b (holotype FI-014153!). Plate 9.

Iguanura corniculata Beccari (1889: 187) . Type:— MALAYSIA. Perak, Selama, 3–500 ft., July 1882, Dr. King’s collector 3131 (holotype CAL n.v., isotypes FI-014152!, K-000207995!, SING!).

Iguanura arakudensis Furtado (1934: 273) . Type:— MALAYSIA. Wellesley, Ara Kuda, December 1895, H. Ridley 7027 (holotype SING-0151654!).

Iguanura divergens Hodel (1997b: 7) . Type:— THAILAND. Betong, 800 m, no date, D. Hodel & P. & R. Vatcharakorn 1743 (holotype BK n.v.).

Iguanura belumensis Lim (1998 a: 52) . Type:— MALAYSIA. Perak, Belum F. R., 1992, C. K. Lim PSM 1281 (holotype KEP-169972!, KEP-169973!, KEP-21596!).

Stems 1.7(0.5–3.3) m long, 0.7(0.4–1.2) cm diameter, solitary or clustered. Leaf sheaths 10.4(6.5–17.5) cm long, tubular, mostly closed opposite the petiole, cleanly falling, covered with a thin layer of indumentum; ocreas well-developed, separating early into fibers and disintegrating; petioles 13.4(4.5–27.0) cm long; rachises 31.7(13.5–48.0) cm long; leaves divided, rarely undivided, not rounded at the apex, with a deep split, leaf veins diverging, rarely parallel; adaxial leaf veins not prominent, triangular in cross-section; pinnae 4(1–6) per side of rachis; middle pinna 15.9(10.0– 25.0) cm long, 5.1(2.1–8.8) cm wide. Inflorescences spicate or branched to 1 order; prophylls and peduncular bracts inserted some distance apart, more or less persistent; peduncles 11.2(3.0–21.5) cm long, not wooly tomentose; rachises 0.5(0.0–4.2) cm long; rachillae 3(1–5), 12.0(4.0–23.0) cm long, 2.0(1.1–3.0) mm diameter, widely diverging from the rachis, proximal part not with distantly spaced triads, glabrous or sparsely to densely tomentose, not filiform with triads sunken in shallow, more or less closely spaced pits; rachilla bracts not elongate; distal triad bracteoles well-developed; distal part of flower pits densely tomentose or less often glabrous; staminate flowers 2.0– 2.5 mm long with blunt apices; anther margins not undulate; fruits 15.2(11.9–20.1) mm long, 5.4(3.6–6.6) mm diameter, narrowly ovoid, often curved, sometimes curved over at apex, not ridged, the surfaces drying pebbled, white, orange, or crimson; endocarp circular in cross-section; endosperm homogeneous.

Distribution and habitat:—Southern Peninsular Thailand and northern Peninsular Malaysia in lowland Dipterocarp forest, tropical lowland evergreen forest, or wet forest at 275(30–1,125) m elevation (Fig. 13). Kiew (1976) considered I. polymorpha to be present in Borneo. The specimen (Purseglove P.5278) on which this was based is from central Sarawak (Bukit Mersing, Tau Range). It has ellipsoid, curved fruits with ridges, and is here considered to represent I. curvata . However, Dr. Saw Leng Guan (pers. comm.) has photographed a living plant in the Semenggoh Arboretum in Sarawak that appears to be I. polymorpha , and the fruits appear non-ridged (perhaps because fresh fruits do not show the ridging present in dried fruits). The question of I. polymorpha in Borneo is unresolved.

Taxonomic notes:— Preliminary species Iguanura polymorpha was polymorphic for eight variables (stem branching, leaf sheaths, leaf venation, orders of inflorescence branching, rachillae tomentum, distal triad bracteoles, pit tomentum, and fruit shape). Seven of these were treated as traits, and the other (leaf sheaths) was used to split preliminary species I. polymorpha into two phylogenetic species, I. polymorpha and I. thalangensis . Iguanura polymorpha is characterized by its well-developed ocreas, non-prominent adaxial leaf veins, and narrowly ovoid, often curved fruits. Kiew (1976) reported seeds of I. polymorpha to be weakly ruminate. However, all the seeds examined here have homogeneous endosperm.

Iguanura corniculata , included by Saw (2023) as a synonym of I. polymorpha , was initially distinguished by its narrow fruits that are curved over at the apices. Whitmore (1970) was the first to question the difference between I. corniculata and I. polymorpha , and Lim (1998 a) illustrated fruits of I. corniculata , clearly showing their intermediate nature.

Iguanura polymorpha is one of the most variable and complex species in the genus.

Subspecific variation:— The kelantan morphotype occurs in the south-central part of Kelantan state in Peninsular Malaysia, often at the base of limestone hills. It is also somewhat morphologically separate. Its leaves are oblong-shaped, as in the parvula and speciosa morphotypes of I. parvula , but are usually divided with 2–3 pinnae per side of the rachis, and the distal pinna is much wider than the others. One specimen ( Wan Syafiq FRI 90233) has both divided and undivided leaves. Specimens are scored as having diverging leaf venation, although this is difficult to score. It almost appears as if the narrower, proximal pinna could be scored as having diverging venation and the wider, distal one as parallel. Inflorescences have 1–3 rachillae.

Saw placed specimens of the kelantan morphotype, with one exception, in I. polymorpha . The exception ( Wan Syafiq FRI 90233) was placed in I. parvula . These placements reflect the intermediate appearance of the leaves of the kelantan morphotype. They have the small size and shape of the parvula and speciosa morphotypes but are divided as in I. polymorpha . This is an example of the difficulty of scoring characters and delimiting taxa in Iguanura .

PLATE 9. A. Iguanura polymorpha , habit, Thailand (image by R. Vatcharakorn). B. Iguanura tenuis , habit, Thailand. C. Iguanura thalangensis , habit, Thailand. D. Iguanura wallichiana , habit, Thailand.

There are a few, somewhat aberrant specimens, previously included in I. belumensis and I. divergens . Lim (1998 a) considered Iguanura belumensis to be similar to I. polymorpha . The type specimen, from Belum Forest Reserve, has large inflorescences branching to two orders and filiform rachillae, but another specimen (Dransfield 7342), also from the type locality, does not have filiform rachillae. Lim also included another specimen (Mhd. Shah MS 3369) from Bujang Melaka. This and two other specimens (Avé 132, Ridley 9803) from the same locality are here considered to be possible hybrids between I. polymorpha and I. wallichiana . Two specimens (Whitmore FRI 0633, F. Ng FRI 6134) from Gunung Bubu are here considered to be I. brevipes . Excluding these, I. belumensis is represented by the two specimens from the type locality, and these are here considered to be hybrids between I. polymorpha and I. wallichiana .

Hodel (1997b) considered I. divergens to be very similar to I. wallichiana , and I. polymorpha is also known from this region. The type specimen of I. divergens is here considered to be a possible hybrid between I. polymorpha and I. wallichiana . Four other specimens (Siti Munirah FRI 76439, Wan Syafiq FRI 93747, B. Perumal FRI 41681, Mhd. Shah 3369), included by Saw (2023) in I. divergens , are problematic. They tend to have longer, narrower rachillae than typical I. polymorpha . They occur sympatrically with I. wallichiana and their morphology suggests they are also hybrids.

From the distribution of these potential hybrids, there may be a hybrid zone between I. polymorpha and I. wallichiana in northern-central Peninsula Malaysia.