Convex leaf kamala (Mallotus bullatus) resembles M. philippensis var. reticulatus and M. philippensis var. philippensis

NEWS - Convex leaf kamala (Mallotus bullatus M.T.An & J.H.Yu, sp. nov.), a species new to science discovered in Guizhou, China, based on morphological, micromorphological, and molecular evidence resembles Mallotus philippensis var. reticulatus and Mallotus philippensis var. philippensis.

Mallotus was established by De Loureiro in 1790 based on Mallotus cochinchinensis Lour. (Loureiro 1790). It currently consists of about 150 species, mostly shrubs or trees, distributed in tropical and subtropical regions of Asia, Australia, and the Pacific with a few species found in tropical Africa and Madagascar.

In 2023, during a botanical survey at Maolan National Nature Reserve in Guizhou, Ming-Tai An and Jiang-Hong Yu from Guizhou University in Guiyang and colleagues discovered a possible new species of Euphorbiaceae. Field investigations and specimen collection led to the conclusion of the new taxon.

Mallotus bullatus is a shrub, 1.5–2.5 m tall; twigs, young leaves, and inflorescences densely covered with yellowish-brown disc-shaped glandular hairs. Leaves simple, alternate, ovate or lanceolate, 5–18 (-22) × 3–6 cm, thickly papery, apex acuminate, base rounded or cuneate, margins entire or nearly so, sometimes bearing red glands, surface bullate, upper surface glabrous;

Lower surface densely greyish-yellow clustered-tomentose, with long soft solitary or clustered hairs on the veins, and scattered red disc-like glands; basal veins 3, lateral veins 3–4 pairs, looped and joined near the margin; extrafloral nectaries, 2–4, brown, near the base; petiole round 2–5 (-9) cm long, slightly pulvinate at both ends, covered with clustered hairs.

Inflorescences racemose, terminal, solitary or clustered, solely staminate or pistillate, or mixed with pistillate flowers in lower part and staminate ones in upper part; sometimes apparently bisexual flowers also present.

Staminate inflorescences 5–10 cm long, bracts ovate, ca. 1 mm long, pedicel 1–2 mm long, calyx lobes 5, oblong, ca. 2 mm long, densely covered with stellate hairs, with red disc-like glands; stamens 28–30.

Pistillate inflorescences 3–8 cm long, bracts ovate, about 1 mm long; pedicels ca. 1–2 mm long; calyx lobes 4, ovate, densely covered with stellate hairs outside, ca. 3mm long; ovary hairy, stigmas 3 split, 3–4 mm long, stigmas densely set with feather-like papillae on upper surface; some pistillate flowers sometimes bisexual, then with 1 or 2 stamens, the filaments almost as long as the anthers.

Bisexual inflorescences 5–10 cm long, with 3–6 staminate flowers at the apex, lower part entirely pistillate; bracts ovate. Capsule subglobose, with spines, ca. 6–8 mm in diameter, fruit wall thickness ca.1–2 mm, 3 carpellate, densely covered with red disc-like glands; seeds black, ovate or globose, naked with late mature stage.

M. bullatus can be distinguished from M. philippensis var. reticulatus and M. philippensis var. philippensis of leaves with a bullate surface, sometimes containing red glands, male flowers 5 sepals, fruits with spines, tricolporate pollen grains with a clear groove containing a protrusion in the pit, leaf vein hairs scattered and clustered abaxially 0.1–0.8 mm long.

This new species is only known from the karst landscape in Libo County, Guizhou Province, China, at an elevation of 700–900 m. Flowers from April to May and fruits from May to August. "Bullatus" refers to the convex leaf areola. Simplified Chinese: 荔波野桐; Chinese Pinyin: lì bō yě tóng.

During 2023–2024, researchers sampled M. bullatus population and found two additional distribution points near the original discovery site of the species. Each location contained about 30 plants.

The habitat of M. bullatus is mostly in karst scrub, which is spread from the foothills to the middle of the mountains. The habitat of the plant has poor soil fertility, low water retention capacity and frequent drought conditions. The researchers suggest the status of the new species as Data Deficient “DD”.

Original research

Yu J-H, Chen Z-R, An M-T, Yu D-L, Liu F, Xu J, Tang Y-B, Wang Y-R, Zou H-K (2024). Mallotus bullatus (Euphorbiaceae), a new species from Southwest China based on morphological characters and phylogenetic evidence. PhytoKeys 249: 13-25, DOI:10.3897/phytokeys.249.131824

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