Calamus erythrocarpus W.J.Baker & J.Dransf.

Baker, W.J., Barfod, A.S., Cámara-Leret, R., Dowe, J.L., Heatubun, C.D., Petoe, P., Turner, J.H., Zona, S. & Dransfield, J. (2024) Palms of New Guinea. Royal Botanic Gardens, Kew, Richmond. 726 pp.

Morphology General Habit

Moderately robust, multi-stemmed rattan climbing to ca. 40 m

Morphology Stem

Stem with sheaths 12–23 mm diam., without sheaths to 9–13 mm diam.; internodes 24–40 cm

Morphology Leaves

Leaf subcirrate, 70–97 cm long including subcirrus and petiole; sheath mid-green when dry, with thin, pale grey indumentum, almost unarmed, with very few, scattered, minute, upward-pointing spines to ca. 0.5 mm long; knee 24–28 mm long, unarmed; ocrea 7–13 mm, a low, tightly sheathing, unarmed, leathery crest, persistent; flagellum to 2.2 m; petiole 2–7 cm long; leaflets 8–11 each side of rachis, arranged subregularly, rather widely spaced, broadly lanceolate, usually hooded, longest at base 23–37 × 2–5 cm, mid-leaf leaflets 22–34 × 3–5 cm, apical leaflets highly reduced to a remnant 2.2–3.7 × 1–2 cm, or even reduced to a fibre-like structure ca. 1.2 × 0.1 cm, leaflets unarmed, with the exception of a very few, marginal bristles near apex of some leaflets; cirrus absent

Morphology Reproductive morphology Inflorescences

Inflorescence erect, possibly arching when mature, 37–55 cm long including ca. 9–20 cm peduncle, lacking flagelliform tip, branched to 2 orders in the female and 3 orders in the male; primary bracts tubular, split to base by emerging primary branches, usually remaining tubular at tip, unarmed; primary branches 4–6, to 6 cm long, male rachillae 3–10 × ca. mm, female rachillae 3–27 mm × 1–2 mm

Morphology Reproductive morphology Fruits

Fruit solitary, ellipsoid, ca. 16 × 11 mm, scales red, with eroded margins

Morphology Reproductive morphology Seeds

Seed (sarcotesta removed) ca. 9 × 8 × mm, ellipsoid with deep lateral pit; endosperm homogeneous.

Distribution

Foothills of the Owen Stanley Range, south-eastern New Guinea.

Ecology

Lowland forest on lower slopes and valley bottoms, ca. 460 m.

Vernacular

Ohana (Goari). None recorded.

Conservation

Critically Endangered. Calamus erythrocarpus is known from only two sites. Deforestation due to logging concessions is a major threat to this species. Its close proximity to Port Moresby may also pose additional risks.

Recognition

Calamus erythrocarpus can be immediately distinguished by its apical leaflets that are highly reduced to a remnant no more than 4 cm long, which in one specimen is reduced to a fibre-like structure, the leaf apex then resembling a short cirrus. The apical leaflets of C. maturbongsii are more typical and may be free or united up to one quarter of their length. The inflorescences of C. erythrocarpus are recorded to be shorter than those of C. maturbongsii (37–55 cm vs. 62– 81 cm). The splitting rachis bracts of C. erythrocarpus do not tatter as they do in C. maturbongsii. The primary branches of C. erythrocarpus female inflorescences bear fewer rachillae (up to nine in C. erythocarpus, compared to up to 17 in C. maturbongsii). It is remarkable that these two very similar species are disjunctly distributed at opposite ends of New Guinea. Calamus erythrocarpus, on the other hand, is reported to occur within a few kilometres of other species in the C. anomalus group. Calamus erythrocarpus is a member of the C. anomalus group (see under C. anomalus). Calamus erythrocarpus and C. maturbongsii appear to be very close relatives within the group, although both share the unusual inflorescence morphology with all other species in the group (Baker & Dransfield 2002b, Baker & Dransfield 2017). Similarities that unite C. erythrocarpus and C. maturbongsii include the moderately robust, multi-stemmed habit, the leaf structure (few broadly lanceolate, hooded leaflets, longest leaflets at the base of the leaf), the almost unarmed leaf sheaths with only few, minute spines, and the robust inflorescence relative to other members of the group. Their fruit are also similar in shape, in orange-red colour and in the structure of their rather flat scales with erose margins.