Typhonium bicolor Luu, X.B.

Luu, Hong Truong, Tran, Ngoc Toan, Nguyen, Tran Quoc Trung, Phan, Cong Sanh & Nguyen-Phi, Nga, 2024, Two new species of Typhonium (Araceae) with bicolored staminodes from Central Vietnam, Phytotaxa 633 (2), pp. 163-170 : 164-166

Typhonium bicolor Luu, X.B. Nguyen-Le & N.T.Tran, sp. nov. ( Fig. 1)

The new species is most morphologically similar to T. kbangense in having fully pedate leaves with 7-leaflets and bicolored down-curved staminodes but differs from the latter in having pinkish (versus green) petioles with (versus without) greenish-brownish mottling, oblong-elliptic and thick (versus elliptic to lanceolate and thin) leaflets, a basally orange, apically yellow (versus entirely brown) spadix appendix, yellowish and elliptic flattened (versus orange yellow and (sub-)globose) anthers with lateral (versus apical) dehiscence, 6–7 mm long and pink (versus 7–12 mm long and crimson red) staminodes with a verrucose (versus concave slitted) surface and a bright yellow and obtuse or truncate (versus a bright yellow to white and acute) apex, oblanceolate (versus ovoid) ovaries and a stipitate (versus sessile) spadix appendix.

Type:— VIETNAM. Da Nang City, Lien Chieu District, Hoa Hiep Bac Commune, southern part of Hai Van Pass, 16 ⁰11’10”N 108 ⁰07’44”E, 570 m elevation, March 11, 2023, Luu Hong Truong, Nguyen Van Nguyen & Tran Ngoc Toan HV01 (holotype SGN!, isotype PHH!).

Herb 25–30 cm tall; tuber rhizomatous, underground, elongate, cylindrical, 2.5–4.0 cm long, 1.2–1.4 cm in diameter, producing later shoots and many stout roots, beige outside, cream white inside. Leaves 1–2. Petiole smooth, 15–25 cm long, 4–6 mm diameter, light pink with greenish-brownish mottling. Leaf blades fully pedate with 7-leaflets, leathery, thick, green above, pale green beneath; leaflets oblong-elliptic, 6–13 cm long, 1.8–3.1 cm wide, acuminate at apex, lateral venation of 9–13 pairs, outermost leaflets sometimes reduced to be orbicular auricles. Inflorescence 1, foetid smelling; peduncle underground, longer than petiole sheath, white, 6–8 cm long, 3.2–3.7 mm in diameter, covered outside by a cataphyll 6–7 cm long; spathe 25–30 cm long; spathe tube aboveground, separated from the limb by a constriction, ovoid, 2.0– 2.3 cm long, 1.3–1.7 cm diameter, outside brown with many darker brown dots, inside brownish-greenish; spathe limb elongate, narrowly lanceolate, 23–27 cm long, 2.8–3.2 cm wide at base, ending with acute tip, outside and inside greenish-brownish; spadix equaling spathe in length, sessile, erect; female zone conical, 3.0– 3.5 mm high, 7–8 mm in diameter at base, 5–6 mm in diameter near apex, light purple, with 5–6 rows of crowded pistils; ovary obovoid, 2 mm high, 1 mm in diameter, translucent cream with many purple dots at apex, 1-locular, with 1 basal ovoid ovule hold obliquely on a funicle; stigma sessile, disciform, 0.3 mm diameter, light purple, obscurely tuberculate; sterile zone contiguous with female zone, 20–22 mm long, lower part covered with bicolored (apex and base of different colors) staminodes, 7–8 mm long, upper part naked; staminodes stick-shaped, 6–8 mm long, ca. 0.6– 0.7 mm in diameter, perpendicular to the spadix axis, downward curved or folded toward axis, pale purple, verrucose and with yellow, slightly flattened and obtuse or truncate apex; male zone cylindrical, 7–9 mm long, ca. 5 mm in diameter; stamens free, densely arranged; thecae yellowish, elliptic, flattened, dehiscent by lateral pore; pollens light orange; appendix stipitate, orange, yellow toward the apex, longitudinally fissured, filiform and tapering to apex, 23– 25 cm long, 3.5–4.0 mm in diameter at base, with acute apex and irregularly lobed and flaring base. Fruits unknown.

Etymology: —The species is named after its bicolored staminodes (pale purple with yellow apex).

Vietnamese name: —Bán hạ hai màu.

Ecology: —The new species grows in clumps on humus soils between granite crevices in open spaces of a degraded deciduous shrubby vegetation. Flowering was seen in March.

Distribution: — Typhonium bicolor has been recorded only from the type locality.

Proposed IUCN conservation status: — Critically Endangered B1+B2b, C2a(ii),b ( IUCN Standards and Petitions Subcommittee 2022). The species was found in small scattered clumps of less than 10 mature individuals each on Hai Van Pass. Both Extent of Occurrence (EOO) and Extent of Occupancy (AOO) are estimated to be less than 10 km 2. Little regeneration was found. Its habitat has been and is going to be severely degraded and fragmented by human impacts and often fired. Conservation measures should be urgently employed.

Notes: — Typhonium bicolor looks very much like T. kbangense , which was described from the Central Highlands. Besides the bicolored staminodes, both taxa share many other characters in common: the size of the plant, leaves and inflorescence, the 7-lobed pedate leaves and the general appearance and structure of floral parts such as peduncle, spathe, spadix appendix, male, sterile and female parts and staminodes. However, they can be distinguished by several key characters as stated in the diagnosis. More morphological differences are summarized in Table 1. The spadix of T. bicolor is also similar to that of T. bachmaense but the later has green to violet-brown petioles without mottling, leaf blades with 5 elliptic to elliptic-lanceolate and thin leaflets, brown to yellowish brown spadix appendix with brown stipe, pale pink and elongate anthers dehiscent by apical pores, clavate staminodes and elongate or lageniform and translucent white ovaries with red stigma. Without flowers, T. bicolor may be confused with Amorphophallus lanceolatus (Serebryanyi 1995: 230) Hetterscheid & C.Claudel in Hetterscheid et al. (2012: 43) by its leathery, thick, dark green and oblong-elliptic leaflets and tough mottled petiole.

The fully pedate leaves with 7 oblong-elliptic and thick lobes make this species distinct from the other Typhonium species with bicolored staminodes. Furthermore, the staminodes in T. bicolor are different from those in the other closest congeners, which are directed straight upward or slightly curved and red with a light yellow acumen in T. blumei , few, short and subulate to slightly clavate in T. culaochamense (described below), straight or recurved, ca. 3 mm long and red with white acumen in T. filiforme , spathulate-linguiform or subulate and white with or without purple acumen in T. flagelliforme and rod-shaped and pink with a dirty yellow acumen in T. ramosum .