AMORPHOPHALLUS CALLADOI

PROTOLOGUE: Amorphophallus calladoi , published in Phytotaxa 740(2): 217-222 (2026).

Amorphophallus calladoi R.Bustam., M.N.Tamayo & Pelser, sp. nov. Amorphophallus calladoi is unique among Amorphophallus species in having a combination of the following characters: a ca. 1:2 peduncle to spathe ratio, a spreading and broadly triangular spathe with a deep and distinct constriction, a rugose appendix, stamens with rounded pores, and a trilobed stigma. Type: Philippines, Luzon Island, Aurora Province, Municipality of Maria Aurora, Barangay Villa Aurora, 828 m elevation, 13 April 2012, J.R.C. Callado 404 with J.F. Barcelona and P.B. Pelser (holotype PNH 259193, barcode PNH-01-0001589).

DISTRIBUTION: .

DISTRIBUTION NOTE: Philippines: Luzon - the Aurora Memorial National Park in Aurora Province, where it has been found on several occasions, and the adjacent Pantabangan-Carranglan Watershed Forest Reserve in Nueva Ecija, where it has so far been seen only in leaf.².

SPECIES DESCRIPTION:

Tuber depressed globose, 1-4 by 1-3 cm. Leaf solitary. Petiole 35.3-50.0 cm long and 1.0-1.5 cm across, smooth; the ground colour rusty to reddish green with white to greyish lichen-like patches and scattered dark green spots throughout, the markings elongate-elliptic, circular or irregular, pale white or dull silver. Lamina about 33.7 cm across. Leaf bulbil half-epiphyllar or epiphyllar, obpyramidal, 0.5-1 cm across. Rachis winged towards the tip from the second branching, the basal part more or less winged with a few nearly stalked leaflets. Leaflets ovate-elliptic to elliptic-lanceolate, 4-10 by 2-4 cm; the base acute, the margin entire and shallowly wavy, the apex acuminate with an acumen 2-3 cm long; midvein raised beneath and shallowly sunken above, with whitish or silvery blemishes along its edges; lateral veins in 8-12 pairs, raised beneath and shallowly sunken above.²

INFLORESCENCE:

Inflorescence solitary; bracts two, linear-lanceolate, 11.6-15.9 by 1.5-2.5 cm; the peduncle to spathe ratio about 1:2. Peduncle smooth, 7-7.5 cm long and 1.0-1.2 cm across, white or pinkish tinged red and brown. Spathe spreading, broadly triangular when spread, about 15 by 10 cm, the margin entire and smooth, membranous, with a deep and prominent constriction separating base from limb; the base tubular-urn-shaped and arching over, 5-6 by 5-6 cm, smooth on both surfaces, darker red outside and burgundy with scattered reddish spots within; the limb spreading, channelled towards the constriction and less so towards the apex, the margin wavy, 8-9 by 8-10 cm, the ratio of base length to limb width 1:1.3-1.5, smooth, burgundy to claret outside and carmine red within, turning pale maroon towards the constriction. Spadix sessile, shorter than the spathe, about 12.6 cm long and 0.7 cm across, white densely speckled with minute pink spots, some running together into irregular blotches. Female zone cylindric, 2.7-3.0 by 1.4-1.6 cm, the flowers slightly congested; ovary oblate in life and depressed globose when dried, 1.4-1.6 by 1.1-1.3 mm, one-chambered, pale yellowish or greenish at the base and light burgundy towards the base of the style; style terete and slightly widened towards the stigma, 3.8-4.5 mm long and 0.35-0.60 mm across, smooth, wine-coloured at the base and darker towards the tip; stigma three-lobed, 1.5-1.6 by 0.8-0.9 mm, white or pale yellow, minutely papillate, the upper two lobes conical, 0.5-0.7 mm long and alike in size, distinctly smaller than the lower lobe, which is ovoid and 0.7-1.0 mm long. No staminodes between the female and male zones. Male zone touching the appendix, cylindric, 3.7-4.0 by 0.3-0.5 cm; male flowers slightly congested, 1.2-1.5 by 1.0-1.2 mm, white to pale yellow tinged pink, of 3-4 stamens low on the zone, 2-3 in the middle and 1-2 towards the top; filaments connate, 0.2-0.3 mm long; anthers oblong, 0.3-0.4 mm across, the thecae opening by terminal rounded pores. Appendix consistently cylindric with no visible constriction near the male zone, 50-60 mm long and 1.6-3.6 mm across, rugose, carmine at the base turning maroon and then brownish red towards the apex, the apex blunt or obtuse; its staminodes elongate-pyramidal over the basal half, becoming round-pyramidal from the midpoint to about three-quarters of the length, prominently protruding at the base and reduced to slight bumps towards the tip, 1.3-3.8 by 0.5-0.8 mm, with dark carmine vestigial pores 0.10-0.11 mm across. Fruits have not been seen.²

ECOLOGY:

Grows on the forest floor on clay soil under a thick layer of humus, in well-shaded to partly open places among dense thickets of shrubs, in both primary and secondary forest. Recorded between 680 and 828 m - higher than most Philippine species of the genus, Amorphophallus minimus excepted. It flowers in April.²

ETYMOLOGY:

Named for John Rey C. Callado, a native of Cabatuan in Iloilo, who collected the type and brought the plant to the authors' attention. The epithet is a noun in the genitive.²

NOTES:

1. No single character defines the species. It is separated by a combination: a peduncle about half the length of the spathe, a spreading and broadly triangular spathe with a deep and distinct constriction, a wrinkled appendix, stamens whose pores are round rather than slit-like, and a three-lobed stigma.²

2. The stigma is unequally three-lobed - two small conical lobes above and a larger ovoid one below.²

3. It belongs to an informal group of five Philippine species whose spadix appendix carries prominently protruding staminodes, giving it a wrinkled look. Three of those, including this one, have short inflorescence stalks of 10 cm or less.²

4. ⚠ Its closest match is a species nobody has seen for a century. Amorphophallus luzoniensis has not been re-collected since it was found in limestone crevices along the Abulug River in Cagayan in 1912, and the paper states plainly that its characters are not well understood. A plant from Ilocos Norte may be the same species, but those populations were destroyed by typhoons in 2016 and 2018. Against it, Amorphophallus calladoi has a longer peduncle-to-spathe ratio, a shorter spadix, a longer style, a three-lobed rather than ovoid stigma, round rather than slit anther pores, and an appendix of even width rather than one tapering to the tip.²

5. It also resembles Amorphophallus fontarumii, from which it differs in a shorter peduncle, a spathe with a deep constriction rather than none, a spadix shorter than the spathe rather than longer, a far longer style - 3.8-4.5 mm against about 0.4 mm - and a three-lobed rather than irregularly shield-shaped stigma.²

6. The type was gathered in 2012 and the species published in 2026. Fewer than ten mature plants have been recorded in the national park, with about twenty more seen in leaf in the neighbouring reserve, and the authors assess it as Data Deficient.²

7. It is the twenty-second species of the genus known from the Philippines, and all but one of those are found nowhere else.²

REFERENCES:

1. Phytotaxa 740(2): 217-222 (2026) — protologue.