Amorphophallus bantae J.T.Scholten, D.W.Livingston & Sizemore, 2024

Scholten, Justin, Livingston, David & Sizemore, Mary, 2024, A new Amorphophallus (Araceae) species from Thailand and an updated key to the Longituberosus and Saraburiensis subclades, Phytotaxa 633 (2), pp. 101-107 : 102-105

Amorphophallus bantae J.T.Scholten, D.W.Livingston & Sizemore , sp. nov. ( Figs. 1 , 2 )

Similar to Amorphophallus tenuistylis in general morphology and habit, but differs by having an overall smaller inflorescence, elliptic spathe with vertical stripes and a mucronate limb apex (rather than a lanceolate unstriped spathe with an acute apex), a spadix as long or slightly shorter than the spathe (in contrast to a spadix distinctly longer than the spathe), and congested pistillate flowers with shorter (ca. 1 mm long) styles (as opposed to sparsely arranged pistillate flowers with long (3–4 mm) styles).

Type: — UNITED STATES OF AMERICA. Florida, Fort Myers, from a plant cultivated by D.W.Livingston from the collection of John Banta, 28 Apr. 2023, Justin Scholten 366 (orig. living coll. : THAILAND. Sa Kaeo Province, North of Ta Phraya District , 125 m, N14°7’21.23” E102°40’33.48, 15 Oct. 2000 (holotype BH!)

Tuber napiform to elongate, 5–8 cm long, 3–5 cm diam. Petiole 25–32 cm long, 0.8–1.2 cm diam, surface glabrous, green with numerous vertical whitish/light green stripes. Lamina 41–46 cm diam, rachises narrowly winged proximally and distally; leaflets ovate to elongate elliptical, 22–32 cm long, 24–28 cm wide; foliolules ovate to lanceolate, adaxial surface slightly darker green than abaxial surface, collective vein distant from margin, 32–40 foliolules per leaflet. Inflorescence solitary; peduncle 28–34 cm long, 6–9 mm in diam at the base, glabrous, with purple vertical stripes grading to green, 0.25–2.00 mm in diam, and whitish ovoid mottles, ca. 0.25 mm in diam. Spathe elliptical-cuneate, 14–16 cm long, 2.5–3.5 cm in diam, erect, base and limb separated by a shallow constriction, exterior dark green with purplish vertical stripes, 0.25–2 mm in diam, and whitish ovoid mottles, 0.25 mm in diam (as peduncle), limb interior as exterior but without stripes or mottles, base interior light purple/red and distinctly verrucose. Spadix sessile, as long or slightly shorter than spathe, 13–15 cm long; pistillate zone cylindric, 2–3 cm long, 0.75–1.25 cm diam, pistils crowded; staminate zone cylindric, 5–6 cm long, 0.75–1.25 cm diam, stamens crowded; appendix cylindric, 5.5–6.5 cm long, 0.4–0.6 cm diam, purplish-brown, glabrous toward apex, slightly corrugated at base, apex mucronate, emitting a vague citrus-like odor at anthesis. Ovaries depressed-globose, 1.8–2.1 mm diam, 1.2–1.4 mm long, light green, 2–3-locular; style ca. 1 mm long, slightly angulate, purple; stigma depressed, 1.2–1.4 mm diam, 0.2–0.3 mm high, 2–3 lobed, surface covered densely in fleshy projections, yellow to pale brown. Male flowers consisting of 2–6 stamens, lowermost stamens slightly enlarged, 2–5 mm long, 2–5 mm diam; filaments ca. 1 mm long, up to 2mm long in lowermost flowers; anthers reddish-purple, 1.5–2.5 mm long, 1.25–2 mm diam, connective slightly depressed, pores apical, elongate. Fruits not observed.

Climate:— The province of Sa Kaeo experiences a seasonal tropical climate with the rainy season typically lasting from May through October, dry season from November through January, and summer from February through April. The mean annual air temperature in Sa Kaeo is among the highest of the provinces in this region, averaging 28.4° C, while the average humidity and rainfall is among the lowest, 74.5% and 1404 mm respectively ( Phattraporn et al. 2016).

Geography:— Sa Kaeo comprises an approximate area of 7,200 square kilometers in southeastern Thailand and is geographically diverse, with both flat plains in the south and the Khao Ban Thad mountains in the north (ranging in elevation from 74 m and 740 m respectively). The mountainous region in the northern sector of the province gives origin to the Bang Pakong River, an ecologically important watershed within the province ( Chaikongthong et al. 2015). The type locality for this species occurs in an open lowland valley between the Khao Sakae Krong (480 m) and Khao Thing Kap (305 m) mountains at an approximate elevation of 100– 150 m.

Distribution: —Known only from this type locality in the Ta Phraya district of Sa Kaeo province, Thailand.

Eponymy: —The epithet of this species honors John Banta, a superb plantsman, for his contribution to Araceae conservation and discovery of this species.

Morphological affinities:— Amorphophallus bantae shares some degree of morphological similarity with all members of the Longituberosus and Saraburiensis subclades within the subgenus Scutandrium , including having an elongate tuber, medium inflorescence size, spathe base interior with elongate papillae, spathe base and limb being separated by little to no constriction, emission of citrus-like odor from the appendix at anthesis, stigmas with pronounced styles, and elongate thecae pores. It differs from A. saraburiensis and A. scutatus in not having sterile synandrodes present between the pistillate and staminate zone and a spadix that is as long or shorter than the spathe (versus distinctly longer)—important diagnostic characters in the genus. Amorphophallus bantae can be easily distinguished from A. tenuispadix and A. albispathus in having a striped spathe and peduncle, reddish appendix, and purple styles. Although similar to A. longituberosus in having a striped spathe and peduncle, short spadix, and 3-locular ovary, A. bantae can be discriminated by the presence of a reddish appendix, purple styles, and depressed ovaries.

Amorphophallus tenuistylis perhaps shares the closest morphological affinity with A. bantae , both species share a mottled peduncle and spathe, reddish appendix, purplish spathe base interior with pronounced warts, 2–3-lobed stigma, and reddish-purple style; however, A. bantae has an overall smaller inflorescence, elliptic spathe with vertical stripes and a mucronate limb apex, a spadix as long or slightly shorter than the spathe, and congested pistillate flowers with shorter (ca. 1mm long) styles (for full comparison, see table 1).

Other specimens examined (paratypes):— UNITED STATES OF AMERICA. Florida, Fort Myers, from a plant cultivated by D.W.Livingston from the collection of John Banta, 13 June 2023, Justin Scholten 425 . From same plant as Justin Scholten 366 (type) (orig. living coll. : THAILAND. Sa Kaeo Province, North of Ta Phraya District, 125 m, N14°7’21.23” E102°40’33.48, 15 Oct. 2000 (paratype BH!) ; Florida, Fort Myers, from a plant cultivated by D.W.Livingston from the collection of John Banta, 28 July 2023, Justin Scholten 455 . From same plant as Justin Scholten 366 (type) and Justin Scholten 425 (paratype) (orig. living coll. : THAILAND. Sa Kaeo Province, North of Ta Phraya District, 125 m, N14°7’21.23” E102°40’33.48, 15 Oct. 2000 (paratype BH!).

Figures

FIGURE 1. General habit of Amorphophallus bantae. A. Inflorescence: front view; B. Inflorescence: back view; C. Tuber; D. Leaf; E. Petiole.

FIGURE 2. Spadix morphology of Amorphophallus bantae. A. Spadix with excised spathe; B. Closeup view of pistillate zone of spadix with partially excised spathe; C. Pistillate flowers; D. Staminate flowers; E. Spathe base verrucosity; F. Longitudinal section of an individual ovary.