Arisaema pulchellum Z.X.Ma, 2025

Ma, Zhengxu, 2025, Materia Revisionis Arisaemarum: III. taxonomic notes and five new taxa of the genus Arisaema (Araceae) from South China, Phytotaxa 697 (1), pp. 47-67 : 61-64

6.1. Arisaema pulchellum Z.X.Ma , sp. nov. ( Figs. 13 , 14 )

Arisaema pulchellum differs from A. lobatum in having a small, creamy white tuber, membranous and somewhat bullate leaf blades, a proportionally larger and slightly galeate spathe limb (limb-tube length ratio = 1: 1.25–1.30, vs. 1: (2.2–) 3.5–4.3 in A. lobatum ), with brochidodromous white striation abaxially, and an appendix gradually narrowed and stipitate, but never crispate at base.

Type: — CHINA. Guizhou Province: Qiannan, Libo County, along road Y006, Maolan, Shishangsenlin, elev. 783 m, 19 March 2024, Y.E.Wang 299 (holotype BAZI!, isotypes BAZI!, E!, PE!).

Perennial lithophyte, seasonally dormant, paradioecious. Subterranean stem tuberous, creamy white, subglobose, to 2.1 cm in diam., strongly deflected during growing season, bearing multiple tubercles. Eophyll unknown. Cataphylls 3–5, membranous, free at distal region (2.1–4.1 cm), connate proximally. Foliage leaf solitary, rarely in pairs; petiole glossy, green and mottled with purple, the proximal 5.4–17.6 cm sheathing into pseudostem, petiolar sheath fully connate; leaf blade trifoliolate, membranous, slightly bullate adaxially; laminae venation broadly brochidodromous, slightly raised abaxially, impressed adaxially; lateral leaflet, oblique, 9.9–16.5 × 4.7–8.4 cm, base subsessile; central leaflet oblong to elliptic, 9.8–11.4 × 4.4–9.4 cm, base narrowly attenuate or obtuse, petiolule 0.8–1.2 cm long, apex attenuate and acuminate. Inflorescence solitary, always held below leaves. Spathe tube pale green abaxially, pale green with purplish longitudinal striation, funnelform, 3.2–4.4 cm long, 0.9–1.6 cm in diam; spathe mouth broadly auriculate, 0.5–0.8 cm wide; spathe limb pale green with obscure brochidodromous white striation abaxially, dark purple with distinct pale green brochidodromous white striation abaxially, suberect, broadly lanceolate, 6.7–9.5 × 3.1–4.1 cm, long acuminate and attenuate to apex, slightly galeate at back; limb-tube length ratio=1: 1.25–1.3 (excluding the apical tail). Spadix dioecious, 4.3–5.4 cm long; female zone unknown; male zone cylindric to subpyramidal, 1.3–2.1 cm long; androecium lax; synandrium consisting 2 bithecal anthers, the cofiliment distinct; thecae dark purple, globose, dehiscing by a short slit resulting in an apical pore; connective inconspicuous; appendix pale green and molted with purple, cylindric, 2.4–3.4 cm long, base gradually narrowed and stipitate, never crispate, apex obtuse. Infructescence and seeds unknown. Anthesis in March.

Distribution: —Karst regions from S Guizhou (Qiannan) to SW Guangxi (Baise and Chongzuo, pers. comm. with B.M.Wang and W.B.Xu), endemic to China, likely in N Vietnam. Possibly a southern relative of A. lobatum .

Eponymy: —The specific epithet “ pulchellum ” stems from the Latin “ pulchellus ”, meaning “beautiful”, in reference to the adorable inflorescence of this species.

Additional specimens examined (paratype): — CHINA. Guizhou Province: Qiannan, Libo, Yongkang , Liangshuijiang , elev. ca. 720, 08 March 2022, Y.F.Deng 31082 (PE[sheet numbers: 2658577, 2658580]!; loc. ibid., Libo , along road Y006, Maolan , Shishangsenlin , elev. 742 m, 21 March 2024, Y.E.Wang 336 (BAZI!, PE!); loc. ibid.,) .

Notes: — Arisaema pulchellum is presumably related to A. lobatum , sharing purplish-mottled petioles, oblique leaflets, unisexual spadices, and a stipitate appendix in common. A. lobatum , a species with relatively limited variation, has been extensively discussed by Gusman (1997). A notable distinction is that A. pulchellum consistently has a small milky-white tuber ( Fig. 14 G-I), while A. lobatum features a bluish-green one ( Fig. 15 B, C ). Observationally, A. pulchellum tends to have thinner and somewhat bullate leaves ( Fig. 13 A-C), whereas A. lobatum has thicker, smoother leaves ( Fig. 15 A ). Their spathe form and color also differ: A. pulchellum displays distinct longitudinal striations, with a spathe limb, slightly galeate, and adorned with striking white anastomosed markings and a limb-to-tube length ratio of 1:1.25–1.3 ( Fig. 14 A–D ). In contrast, A. lobatum has a grayish-orange to pale purple spathe, with a larger limb-to-tube length ratio of 1:(2.2–)3.5–4.3 ( Fig. 15 A, D–G ). Additionally, the appendix base of A. lobatum is typically crispate in both male and female inflorescences ( Fig. 15 H–K ), while in A. pulchellum it is attenuate and never crispate ( Fig. 14 E, F ). It is worth noting that the female plants of A. pulchellum are poorly described, and larger individuals may exhibit more variation in appendix morphology.

Geographically, A. pulchellum and A. lobatum show a clear pattern of substitution. A. lobatum is a widespread species in continental Asia, endemic to subalpine regions from the Hengduan Mountains to eastern China, at elevations of (600–)2000–3300(–4500) meters ( Gusman 1997, Li et al. 2010). It is predominantly a geophyte, rarely found in limestone areas. In contrast, A. pulchellum is an obligate lithophyte, restricted to the Karst regions in Guizhou and western Guangxi, where it prefers habitats of well-drained limestone crevices. Its elevation range decreases from about 780 meters in Guizhou (the type locality) to lower altitudes further south in Guangxi. This clear substitution in both distribution and ecological niche strongly supports the recognition of A. pulchellum as a distinct species.

Figures

FIGURE 13. Habit of Arisaema pulchellum in its type locality, note the color is darkened in the wilted inflorescence in B. A & C are vouched by the holotype, Y.E.Wang 299 (BAZI!), B is vouched by Y.E.Wang 336 (BAZI!).

FIGURE 14. Inflorescence and tuber of Arisaema pulchellum. A. Adaxial spathe surface showing longitudinal purple striation on spathe tube and white anastomosed venation extended to the spathe limb; B–D. inflorescence in different views, note the large spathe-limb with broadly auriculate mouth; E. male spadix; F. androecia connected to a stipitate spadix appendix with a rounded base; G. tubers in dormancy; H, I. tuber in the growing season, note the persistent whitish color. All images are vouched by the holotype, Y.E.Wang 299 (BAZI!).

FIGURE 15. Arisaema lobatum from W Hubei, China.A. Habit of an individual with muculate variation; B, C. tuber, note the bluish green coloration; D–F. inflorescence in different views; G. adaxial spathe surface; H. female spadix; I. male spadix; J, K. the distinctive cristate base of the spadix-appendix.All photos are vouched by Y.E.Wang 700 (BAZI!).