Alocasia roseus Asih & Yuzammi, 2024

Asih, Ni Putu Sri, Erlinawati, Ina, Yuzammi, & Hadiah, Julisasi Tri, 2024, The Araceae of Sumatra I: A new species of Alocasia from Aceh, Indonesia, PhytoKeys 249, pp. 223-229 : 223-229

Alocasia roseus Asih & Yuzammi sp. nov.

Fig. 2 , Table 1

Type

(prepared from a cultivated plant in a private nursery). Indonesia • Aceh, Aceh Besar, Lhoknga, Desa Kueh, Kueh Kemukiman Keude Bieng , PSA 395 (holotype BO! [dried specimens and inflorescences in spirit]; isotype ANDA!) (Fig. 2 ) .

Diagnosis

(Table 1 ). Alocasia roseus is morphologically similar to A. flemingiana and A. arifolia from which it differs by having greyish green adaxial leaves and pale reddish to greenish purple or pale brownish green abaxial leaves, interprimary vein absent, sinus not naked, and pale pink appendix (vs. mid-green to dark green adaxial and green-yellowish / paler abaxial leaves, forming poorly to conspicuous interprimary vein, sinus naked up to 3 cm, and cream / pale apricot appendix).

Description.

Small herb c. 55 cm tall; rhizome erect; leaves several together; petiole 34–38 cm long, pale dull green, glabrous, faintly mottled greenish, sheathing in the lower about 1 / 3 of its length, pale dull green; blades leathery, sagittate, greyish green adaxially, reddish to greenish purple to pale brown greenish abaxially, margin entire; anterior lobe 12.8–14.4 cm long, 9.7–11.6 cm wide, the widest is base of anterior lobe, tip acuminate, 7 mm long; anterior costa with 4–5 primary lateral veins on each side, proximal ones diverging at 76–96 ° on each side then running to submarginal vein, distal primary veins diverging at 40–45 ° on each side, primary vein prominent adaxially then forward to marginal becoming flush to lamina, prominent abaxially, with inconspicuous axillary glands, secondary and tertiary venation flush to lamina adaxially, rather prominent and conspicuous abaxially then running to conspicuous submarginal vein inserted c. 1.5 mm from margin, interprimary collective veins absent; posterior costae diverging at 60–80 °, not naked in the sinus; posterior lobes acute, 6–7.2 cm long; inflorescences soliter or in pair, subtended by green cataphylls and then dried at flower anthesis; peduncle to c. 14.6 cm long, resembling petioles in colour and faintly mottled; spathe c. 9.7 cm long; lower spathe ovoid, yellowish green, c. 2.3 cm long, c. 1.8 cm diam; limb lanceolate, yellow to greenish, erect then tilted 45 ° after 3 days, separated from the lower spathe by a constriction at the base of male flowers or at top sterile interstice (to the midpoint of the male zone); spadix shorter than the spathe, c. 7 cm long, shortly stipitate, 2–4 mm, whitish-green, cylindric; female zone cylindric, 0.9–1 cm long, 0.9 cm wide; ovaries subglobose, green, stigma raised on a style 0.5–1 mm, conspicuously, (2 –) 3–4 - lobed, pale yellow; sterile interstice cream-coloured, not attenuate, 0.4–0.5 cm long, narrower than male zone, with 4–5 whorls of rhomboid synandrodia; male zone cylindric, cream-coloured, 1.1–1.2 cm long; synandria rhombohexagonal to somewhat irregular, with the synconnective overtopped the thecae; thecae opening by apical pores; appendix pale pink, gradually tapering to a blunt point, faintly irregularly channeled, c. 3.5–4.2 cm long, slightly wider than the male zone; fruit unknown.

Distribution and habitat.

The species is only known from Aceh Besar, Sumatra Island. It grows on the hillside of the forest, in shade and humid areas.

Etymology.

The specific epithet, roseus, is based on the pale pink appendix of the staminodes found in this new species. This color of the appendix is rarely found in the genus.

Conservation status.

Alocasia roseus is known only from a single locality in the forest near Kueh Kemukiman Keude Bieng, Kueh Village, Aceh Besar Regency, Aceh Province, Indonesia. Since further populations could occur, we prefer to assess these species as Data Deficient ( DD) according to the IUCN Red List criteria (2022).

Notes.

Alocasia roseus belongs to the informal group “ Macrorrhizos ” (sensu Hay 1998) in view of the following showed characteristics: inflorescences in pairs, the spathe constriction aligning with the sterile interstice of the spadix, and the synconnective overtopping the thecae. This species is the second, besides A. balgooyi , in the Macrorrhizos group with no naked sinus in their posterior lobe. Alocasia roseus also has an appendix color that differs from other species in the Macrorrhizos group. Pink being a rare colour of appendix that is found only in A. melo and A. princeps ( Hay 1998) .

Figures

Figure 2. Alocasia roseus: A habit B adaxial leaf C abaxial leaf D petiole E inflorescence with spathe F inflorescence with the spathe removed showing the zonation of reproductive organs G female zone (♀) H sterile interstice zone (s) I male zone (♂) J appendix (a). (Photographed and edited by Ni Putu Sri Asih and Julisasi Tri Hadiah).