Xantolis weimingii Huan C. Wang & Feng Yang, 2024

Yang, Feng, Chen, Chao, Wang, Qiu-Ping, Wu, Jian-Yong, Li, Zhen-Xue & Wang, Huan-Chong, 2024, Xantolis weimingii (Sapotaceae), a new species from the Yuanjiang River basin, Yunnan, southwest China, PhytoKeys 246, pp. 251-263 : 251-263

Xantolis weimingii Huan C. Wang & Feng Yang sp. nov.

Figs 1 , 2 , 3 , 4

Type.

China • Yunnan Province: Yuanjiang County, Wadie village, Luozhi village , near the junction of the Yuanjiang River and Hedihe River , 23 ° 25 ' 51.9 " N, 102 ° 18 ' 42.4 " E, alt. 1100 m, 14 April 2022, C. Chen & Z. X. Li YJ 19450 (holotype: YUKU 02074716 !; isotypes: YUKU!) .

Diagnosis.

Xantolis weimingii is most similar to X. tomentosa (Roxb.) Raf. , but can be easily distinguished by its ovate or obovate (vs. elliptic or elliptic-oblong in X. tomentosa ) leaves, base broadly cuneate or nearly round (vs. cuneate), apex acute or acuminate (vs. obtuse, short obtusely or acutely acuminate), corollas entirely glabrous (vs. densely hairy at throat), 7.7–9.7 (vs. 4–8) mm long, lanceolate staminodes, ca. 5 (vs. 3–3.5) mm long, apex acuminate into an awn, fringed at the base (vs. broad base, not fringed), glabrous (vs. hairy).

Description.

Shrubs or small trees, 2–4 m tall, evergreen, acanthaceous, laticiferous. Bark pale gray, cracked, shallowly and vertically fissured. Branches terete, gray to grayish black; branchlets densely ferruginous arachnoid-lanate, more or less glabrescent when old. Acantha usually axillary, straight, cuspidate, ca. 7 mm long. Petioles 4–8 mm long, with a slight furrow on the adaxial side, densely ferruginous arachnoid-lanate when young, gradually shedding, sparse or glabrescent when old. Leaves ovate to obovate, alternate, leathery, 2.0– 8.5 cm long, 1.5–5.0 cm wide, base broadly cuneate or nearly round, apex acute to acuminate, slightly revolute, margin entire, adaxially dark-green, shiny, densely ferruginous arachnoid-lanate when young, glabrescent, abaxially densely ferruginous arachnoid-lanate when young, gradually faded to gray-green sericeous, or to glabrescent when old; midrib flat, obvious adaxially, prominent abaxially, lateral veins 6–9 pairs, arcuate, rising at an angle of 35 ° – 50 °, apex bifurcation near the margin, irregularly connected, tertiary and reticulate veins convex abaxially. Flowers in 1–5 - flowered clusters in leaf axils or along old branches, pendant. Pedicels stout, terete, 3–4 mm long, densely ferruginous arachnoid-lanate. Calyx cup-shaped, 5 - lobed, rarely 4 - lobed; sepals imbricate, ovate to triangular, 6–7 mm long, 3.5–4.5 mm wide, apex acute, inside white pubescent on the upper part, outside densely ferruginous arachnoid-lanate. Corolla sympetalous, 5 - merous, glabrous, slightly fleshy, tube ca. 4 mm long, lobes lanceolate, 3.7–5.7 mm long, apex acuminate, margin slightly involute, dentate at the base. Stamens 5, adnate to corolla tube at the base, opposite to lobes, filaments white, linear, 2.8–3.5 mm long; anthers sagittate, yellow, ca. 3 mm long, dorsifixed, longitudinal, apex acuminate, base cordate. Staminodes 5, glabrous adnate to corolla tube at the base, alternate to lobes, white, lanceolate, ca. 5 mm long, 1–2 mm wide at the base, apex acuminate into an awn, fringed at the base, glabrous. Ovary ovoid, densely brown pilose; style terete, yellow-green, ca. 8 mm long. Fruits ovoid, oblong or elliptic, with ferruginous arachnoid-lanate hairs, 2.2–4.5 cm long, 1.2–1.5 cm in diam., with persistent calyx, apex sometimes beaked, with persistent style, 1 - seeded. Seeds oblong to ellipsoid, slightly compressed, 2–2.5 cm long, ca. 8 mm in diam., both ends truncate, pericarp woody, shiny yellowish brown, scar elliptic, 1.5–2 cm long, ca. 3 mm wide, whitish.

Phenology.

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

Etymology.

The new species is named after Professor Weiming Zhu (朱维明-Wei Ming Chu, 1930–2023), a renowned botanist from Yunnan University, in recognition of his outstanding contributions to the study of China’s flora of Lycophytes and Ferns and to the Herbarium of Yunnan University (Kunming, China).

Distribution and habitat.

Xantolis weimingii is a rarely and poorly collected species endemic to the central Yunnan province in southwest China. As of now, it has been discovered in four different sites, all situated in the dry and hot valleys of both the Yuanjiang River and its primary tributary, the Luzhijiang River (Fig. 5 ). This new species grows in savanna habitats on the mountain slopes at elevations ranging from 1100 to 1400 m (Fig. 6 ).

Preliminary conservation assessment.

Xantolis weimingii is at a restricted geographic range, with an estimated extent of occurrence ( EOO) of 139.594 km 2 and an area of occupancy ( AOO) of 12 km 2. Four populations of the new species have been discovered: two of them from the same locality (Yimen County), and one in the Yuanjiang National Nature Reserve. Unfortunately, these populations are typically small, ranging from three to a maximum of eight plants. So far, we have not found any saplings or seedlings in the Yuanjiang and Fawu populations, and we judged that the self-renewal capacity of the wild population of this species is low. The other populations in the Luzhijiang River valley at Yimen County are most threatened. The hillside land here is highly degraded and soil erosion is serious due to mining operations. Furthermore, residents had been harvesting the plant for firewood, resulting in the plant becoming a shrub-like appearance. Therefore, Xantolis weimingii is at a high risk of extinction due to a restricted geographic range, fragmented distribution, small population sizes, and fragile living environment. Based on IUCN Red List Categories and Criteria ( IUCN 2022), we suggest a Critically Endangered ( CR) category for the species.

Discussion.

Xantolis weimingii can be easily distinguished from its congeners by the following combination of characters: plants densely covered with ferruginous arachnoid-lanate, leaves ovate or obovate, and staminodes fringed at the base. It is most similar to X. tomentosa (excluding the synonym Planchonella dongnaiensis Pierre ex Dubard ), which is widely distributed in Sri Lanka, India, and Myanmar. However, it differs clearly from the latter by having pale gray (vs. light reddish brown in X. tomentosa ) barks, ovate or obovate (vs. elliptic, elliptic-oblong) leaves, 2–8 (vs. 4–14) cm long, 1.5–5.0 (vs. 2–6) cm wide, base broadly cuneate or nearly round (vs. cuneate), apex acute or acuminate (vs. obtuse or short obtusely or acutely acuminate), 6–9 (vs. 8 – l 6) pairs lateral veins, 4–8 (vs. 3–20) mm long petioles, 3–4 (vs. 4–7) mm long pedicels, entirely glabrous (vs. throat densely hairy) corollas, 7.7–9.7 (vs. 4–8) mm long, lanceolate (vs. lanceolate-oblong or ovate) lobes, staminodes ca. 5 (vs. 3–3.5) mm long, 1–2 mm wide at the base, apex acuminate into an awn, fringed at the base (vs. broad base, not fringed), glabrous (vs. hairy).

Xantolis weimingii is also morphologically similar to X. cambodiana (Pierre ex Dubard) P. Royen from Indo-China. Nevertheless, X. weimingii differs from X. cambodiana in having ovate to obovate (vs. rhomboid-obovate or elliptic, sometimes lanceolate in X. cambodiana ) leaves, base broadly cuneate or nearly round (vs. tapering towards the base), apex acute to acuminate (vs. obtuse, entire or retuse, sometimes short obtusely acuminate), ovate to triangular (vs. ovate or oblong) sepals, 6–7 (vs. 2.5–4) mm long, 3.5–4.5 (vs. 1–2) mm wide, lanceolate (vs. lanceolate or linear) staminodes, ca. 5 (vs. 2–3) mm long, 1–2 (vs. ca. 0.5) mm wide at the base. Xantolis weimingii shares similar fruits with X. assamica (C. B. Clarke) P. Royen , a species occurring in Assam to Bangladesh, but differs from the latter in its 4–8 (vs. 5–15) mm long petioles, ovate to obovate (vs. ovate, elliptic or broadly lanceolate) leaves, 2.0–8.5 (vs. 6–16.5) cm long, 1.5–5.0 (vs. 2–7) cm wide.

Additional specimens examined.

China • Yunnan: Yimen County, near Xiaoluzhi village, the west side of Luzhijiang valley , 24 ° 40 ' 46.21 " N, 101 ° 56 ' 49 " E, 25 September 2015, H. C. Wang et al. YM 241 ( YUKU, plant in vegetative period) ; same location, 27 April 2016, H. C. Wang et al. YM 863 ( YUKU, plant in vegetative period) ; Luzhijiang valley, near Luzhi town , 12 November 2019, H. C. Wang et al. YM 8317 ( YUKU, plant in vegetative period) ; • Luzhijiang valley, near Xiaoluzhi village, Maomao mountain , on the limestone of the dry-hot valley, 24 ° 40 ' 30.9 " N, 101 ° 57 ' 37.21 " E, elev. 1392.46 m, 25 December 2021, H. C. Wang et al. YM 14630 ( YUKU, plant in vegetative period) ; • Eshan County, Dalongtan, the mountain behind the Fawu village , 24 ° 30 ' 14.17 " N, 102 ° 03 ' 46.60 " E, alt. 1400 m, 20 August 2015, H. C. Wang et al. ES 173 ( YUKU, plant during grain-filling period) ; • same location, 9 June 2016, H. C. Wang et al. ES 866 ( YUKU, plant in late flowering and fruiting period) ; • same location, 17 September 2017, H. C. Wang et al. ES 2450 ( YUKU, plant during grain-filling period) ; • same location, 27 April 2022, H. C. Wang et al. YM 16402 ( YUKU, plant in vegetative period) .

Figures

Figure 1. Xantolis weimingii sp. nov. (drawn by Qiu-Ping Wang) A habit B abaxial surface of leaf C adaxial surface of leaf D flower in blooming E anthers F pistil G corolla dissected to show stamens and staminodes H calyx lobes (the upper line is the inner view, the lower line is the outer view) I fruits J side view of seed to show scar K front view of seed.

Figure 2. Xantolis weimingii sp. nov. A habit B trunk showing bark texture C branchlet D abaxial surface of tender leaf E adaxial surface of leaf F abaxial surface of leaf.

Figure 3. Xantolis weimingii sp. nov. A flowering branch B adaxial view of sepals C abaxial view of sepals D corolla dissected to show five stamens and five staminodes E corolla dissected to show five lobes F pistils G – H fruits I front view of seed J side view of seed to show scar.

Figure 4. Holotype of Xantolis weimingii sp. nov. (YUKU- 02074716).

Figure 5. Known geographical distribution of Xantolis weimingii (red stars). Based on all known collections.

Figure 6. Habitat of Xantolis weimingii A habitat of the Yuanjiang population B habitat of the Yimen population C habitat of the Eshan population.