Mallotus bullatus M. T. An & J. H. Yu, 2024

Yu, Jiang-Hong, Chen, Zheng-Ren, An, Ming-Tai, Yu, Deng-Li, Liu, Feng, Xu, Jian, Tang, Yu-Bin, Wang, Yi-Ran & Zou, Hua-Kai, 2024, Mallotus bullatus (Euphorbiaceae), a new species from Southwest China based on morphological characters and phylogenetic evidence, PhytoKeys 249, pp. 13-25 : 13-25

Mallotus bullatus M. T. An & J. H. Yu sp. nov.

Fig. 1

Type.

China. • Guizhou Province, Libo County, Dawn township aquatic animals, 25°19'N, 107°56'E, alt. 700 m, 29 April 2024, Ming-tai An, Jiang-hong Yu, Jian Xu, Feng Liu GZAC-MU-001 (holotype GZAC!) .

Diagnosis.

M. bullatus can be distinguished from M. philippensis var. reticulatus and M. philippensis var. philippensis by having leaves with bullate surfaces and entire or nearly so margins, sometimes bearing red glands, 5 sepals in the staminate flowers, fruits with spines, pollen grains tricolporate with obvious furrows containing protrusions in the apertures, and abaxial leaf scattered and clustered vein hairs 0.1–0.8 mm long (Table 1 ).

Description.

Shrubs, 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 grayish-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 s 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. 3 mm 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.

Distribution and habitat.

This species is known only from the karst landscape of Libo County, Guizhou Province, China (Fig. 2 ), alt. 700– 900 m.

Phenology.

Flowering from April to May, and fruiting from May to August.

Etymology.

“ Bullatus ” specifically refers to the convex leaf areoles.

Local name.

Simplified Chinese: 荔波野桐; Chinese Pinyin: lì bō yě tóng.

Leaf epidermis and palynology.

Pollen grains of M. bullatus are spheroidal, with a size of 22 × 20 μm, L (long) / W (width) = 1.1, and tricolporate. They feature tricolporate furrows containing protrusions (Fig. 3 A – C ). Pollen grains of M. philippensis var. reticulatus are also spheroidal, 19 × 20 μm, L / W ratio 0.95, without distinct furrows (Fig. 3 D – F ). The lower epidermis of M. bullatus leaves bears evenly distributed elliptical glands measuring 100 × 70 μm (E 1 × E 2: length of long equatorial axis × length of short equatorial axis), is densely covered with short clustered hairs, and has long (0.1–0.8 mm long) solitary or clustered hairs on the veins (Fig. 3 G, H ). Similarly, the lower epidermis of M. philippensis var. reticulatus exhibits elliptical glands measuring 80 × 70 μm (E 1 × E 2), is densely covered with short clustered hairs, and has solitary or clustered hairs 0.05–0.15 mm long on the veins (Fig. 3 J, K ). The upper epidermis of both M. bullatus and M. philippensis var. reticulatus leaves is smooth (Fig. 3 I, L ).

Conservation status.

During the period of 2023–2024, we sampled the population of M. bullatus and discovered two additional distribution points near the species initial discovery location (Fig. 2 ). Each site contained approximately 30 plants. The habitat of M. bullatus mainly occurs in karst scrublands, distributed from the foothills to the middle of the mountains. The plant habitat features poor soil fertility, low water retention capacity, and frequent drought conditions. Due to our current insufficient comprehensive assessment of the survival status and threats to M. bullatus , we cannot provide specific distribution information about this population. Therefore, we recommend categorizing M. bullatus as Data Deficient “ DD ” ( IUCN 2022).

Figures

Figure 1. Mallotus bullatus A habitat B, C plant D leaf from above E leaf from below F, G leaf lower surface H – J inflorescences K pistillate flower L, M staminate flower sepals N infructescence with mature capsules O capsule with part removed to show seed P capsule in transverse section.

Figure 2. Geographical distribution of Mallotus bullatus.

Figure 3. Scanning electron microscope images of Mallotus leaf epidermis and pollen grains A – C pollen grains of M. bullatus D – F pollen grains of M. philippensis var. reticulatus G – I lower leaf epidermis of M. bullatus J – L lower leaf epidermis of M. philippensis var. reticulatus.