Iguanura geonomiformis Martius (1845: 229)

Henderson, Andrew, 2025, A revision of Iguanura (Arecaceae, Arecoideae, Areceae), Phytotaxa 690 (2), pp. 135-188 : 157-161

11. Iguanura geonomiformis Martius (1845: 229) . Slackia geonomiformis (Martius) Griffith (1851: 162) . Type:—

Without locality, no date, W. Griffith s.n. (holotype K-000207993!, K 000207994!, isotypes BR n.v., BR image!, P-

00725238 n.v. P image!).

Iguanura malaccensis Beccari (1886: 102) . Iguanura geonomiformis var. malaccensis (Beccari) Ridley (1907: 150) . Iguanura wallichiana subsp. malaccensis var. malaccensis (Beccari) Kiew (1976: 222) . Type:— MALAYSIA. Malacca, Klang, 5 January 1879, F. Kehding 0108 (holotype F-008392!).

Iguanura geonomiformis var. ramosa Ridley (1907: 150) . Lectotype (designated by Saw 2023):— MALAYSIA. Negeri Sembilan, Tampin Hill, May 1894, J. Goodenough 1881 (lectotype SING-0249851!).

Iguanura wallichiana subsp. malaccensis var. elatior Kiew (1976: 224) . Type:— MALAYSIA. Johore, Gunung Belumut, no date, R. Holttum 10299 (holotype SING-0001357!).

Iguanura wallichiana subsp. malaccensis var. humilis Kiew (1976: 223) . Iguanura humilis (Kiew) Lim (1998 a: 37) . Type:— MALAYSIA. Kemaman, Ulu Bendong, 500 ft., 31 October 1936, E. Corner 30095 (holotype SING-0072414!, isotypes BH!, K-1282358!, K-1282359!, L-1407209!).

Iguanura kelantanensis Lim (1998 a: 30) . Type:— MALAYSIA. Kelantan, Gua Musang, Gunong Ayam F. R., 280 m, 26 August 1992, Saw Leng Guan FRI 37607 (holotype KEP-21646!, KEP-167290!, isotype K-001260609!).

Iguanura ruthiae Saw (2023: 102) . Type:— MALAYSIA. Pahang, Krau Wildlife Reserve, Kuala Lompat, 28 April 1970, R. Evans 2870 (holotype KEP-21713!, KEP-171459!).

Stems 0.5(0.01–1.7) m long, 1.1(0.7–1.9) cm diameter, solitary or clustered. Leaf sheaths 10.7(4.8–25.0) cm long, open and more or less persistent, not cleanly falling, covered with a thin layer of indumentum; ocreas well-developed, separating early into fibers and disintegrating; petioles 22.9(3.5–114.0) cm long; rachises 45.3(18.0–130.0) cm long; leaf blades undivided or divided, not rounded at the apex, with a deep split; leaf veins parallel; adaxial leaf veins prominent, rectangular in cross-section; pinnae 3(1–20) per side of rachis; middle pinna 29.2(16.3–46.5) cm long, 4.6(0.7–11.0) cm wide. Inflorescences spicate or branched to 1 or 2 orders; prophylls and peduncular bracts inserted some distance apart, more or less persistent; peduncles 29.1(7.5–66.0) cm long, not wooly tomentose; rachises 2.1(0.0–23.0) cm long; rachillae 3(1–27), 25.4(4.5–66.0) cm long, 2.8(1.0–5.4) mm diameter, on branched inflorescences not diverging from rachis, the proximal, adaxial rachilla surfaces flat, lying close to the flat rachis surface, the proximal part of rachillae with markedly 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 glabrous; staminate flowers 2.0– 2.5 mm long with blunt apices; anther margins not undulate; fruits 11.6(8.9–17.0) mm long, 7.9(6.2–11.3) mm diameter, not ridged, the surfaces drying pebbled, white, whitish, or red; endocarp circular in cross-section; endosperm ruminate.

Distribution and habitat:—Peninsular Malaysia and Sumatra in primary, lowland Dipterocarp forest or swamp forest at 264(20–1,000) m elevation ( Fig. 10 ).

Taxonomic notes:— Preliminary species Iguanura geonomiformis was polymorphic for five variables (stem branching, leaf division, orders of inflorescence branching, rachillae tomentum, pit tomentum). These were treated as traits and then preliminary species I. geonomiformis had a unique combination of qualitative character states and is recognized as a phylogenetic species. It is characterized by its rachillae, on branched inflorescences, not diverging from rachis, with the proximal, adaxial rachilla surfaces flat, lying close to the flat rachis surface, the proximal part of rachillae with markedly distantly spaced triads, and ruminate endosperm. Three other preliminary species, I. humilis , I. kelantanensis , and I. ruthiae , had the same combination of character states and are included.

Iguanura geonomiformis and the closely related I. wallichiana have been treated differently by Kiew (1976), Lim (1998 a), and Saw (2023), although all three recognized a basic division of the specimens into two taxa. Kiew (1976) recognized a widespread and variable I. wallichiana . She considered that characters such as leaf division and inflorescence branching were unreliable for species delimitation. She recognized two subspecies — subsp. malaccensis (i.e., I. geonomiformis ) occurred in the southern part of Peninsular Malaysia and was characterized by spicate or bifurcate inflorescences while subsp. wallichiana (i.e., I. wallichiana ) occurred in the northern part of Peninsular Malaysia and was characterized by branched inflorescences. The two subspecies had overlapping distributions in the central part of Peninsular Malaysia. Within subsp. malaccensis three varieties were recognized by Kiew—a widespread var. malaccensis with divided leaves, a narrowly distributed var. humilis with shorter stems and undivided leaves, and a narrowly distributed var. elatior with longer stems and undivided leaves. Within subsp. wallichiana two varieties were recognized—a widespread var. wallichiana with shorter stems and divided leaves, and a narrowly distributed var. major with longer stems and undivided leaves.

Lim (1998 a) recognized seven species in the complex. For Kiew’s subsp. malaccensis, Lim recognized two species ( I. geonomiformis , I. humilis ), and for Kiew’s subsp. wallichiana he recognized five species ( I. wallichiana , I. diffusa , I. asli , I. kelantanensis , I. piahensis ), with I. wallichiana divided into three varieties.

Saw (2023) recognized six species. For Kiew’s subsp. malaccensis, Saw recognized four species ( I. geonomiformis , I. humilis , I. ruthiae , I. kelantanensis ). For Kiew’s subsp. wallichiana he recognized two species ( I. wallichiana , I. asli ), with I. wallichiana divided into two varieties. Note that Saw (2023) considered I. kelantanensis allied to I. geonomiformis , while Lim (1998 a) considered it allied to I. wallichiana .

Whitmore (1998) considered I. geonomiformis almost always had white fruits and I. wallichiana commonly red.

Variation within the two species is complex. Here various morphotypes of I. geonomiformis are recognized.

Subspecific variation:—The geonomiformis morphotype (based on I. geonomiformis , I. malaccensis , I. wallichiana subsp. malaccensis var. malaccensis , I. wallichiana subsp. malaccensis var. elatior , I. geonomiformis var. ramosa ) occurs in the southern, mostly western part of Peninsular Malaysia and in Singapore. This morphotype has mostly divided leaves and inflorescences with one or a few, narrowly diverging rachillae. The rachillae tend to be relatively thick and are usually densely tomentose. There appear to be three separate populations of the geonomiformis morphotype, a southern, central, and northern one. There are few differences between them, although inflorescences differ slightly amongst the three populations.

The humilis morphotype (based on I. wallichiana subsp. malaccensis var. humilis ) occurs in northern Peninsular Malaysia. It has mostly small, undivided leaves and spicate (rarely bifurcate) inflorescences. There appear to be at least three different populations of this morphotype, western, central, and eastern, each one slightly different from the others, indicating that they have probably arisen independently and are not necessarily closely related. The western population, from Bukit Larut in Perak, occurs at the highest elevations and has undivided leaves with a distinctive, triangular shape and smooth margins, at least proximally. In the central part of the Peninsula, specimens from Kelantan and Pahang have undivided or divided leaves and the margins are praemorse. The eastern population in Terengganu occurs at the lowest elevations and specimens have broad or narrow undivided, less often divided, leaves. A few specimens have bifurcate inflorescences and divided or undivided leaves, and are thus indistinguishable from the geonomiformis morphotype. Some specimens from Sungai Kajang in Terengganu have distinctive, long, narrow, undivided leaves.

The kelantanensis morphotype (based on I. kelantanensis ) occurs in the northern part of Peninsular Malaysia, mostly in Kelantan State. Saw (2023) reported it to be similar to I. geonomiformis but differing in its inflorescences often branching to two orders and more, slender rachillae (7–27 rachillae 1.0– 2.5 mm diameter recorded here). However, leaves are very variable. The label of one specimen (T. Whitmore FRI 15253) states that it comes from “a huge, diffuse, polymorphic population”.

The ruthiae morphotype (based on I. ruthiae ) occurs in the central part of Peninsular Malaysia, in Pahang state (and overlaps with the northern population of the geonomiformis morphotype and with I. wallichiana ). Specimens have divided leaves and relatively thin, scarcely tomentose rachillae with more loosely spaced triads.

There is one particularly unusual specimen (Dransfield 2623) from Jambi in Sumatra, the sumatra morphotype. This has short stems, a large leaf with 10 pinnae per side of the rachis, and a small inflorescence with an exceptionally short peduncle. In this it is similar to the asli morphotype of I. wallichiana . However, rachillae are scored as for I. geonomiformis . All other Sumatra specimens are considered to belong to the I. wallichiana species complex.

Figures

FIGURE 10. Distribution of morphotypes of Iguanura geonomiformis.