Pittosporum napoense Y.S. Huang, Yan Liu & Y.F. Deng, 2024

Pittosporum napoense Y.S. Huang, Yan Liu & Y.F. Deng , sp. nov. Figs. 1 View FIGURE 1 , 2 View FIGURE 2 & 3 View FIGURE 3 (A–D)

Type: — CHINA. Guangxi Zhuang Autonomous Region: Baise City, Napo County, Baisheng Town, Nongbu Village, elev. 1050 m, 19 August 2009, Y.S. Huang & W.B. Xu 091148 (holotype: IBK!, isotypes: IBK!, IBSC!, PE!).

Diagnosis: —The new species is morphologically similar to P. kerrii in the paniculate inflorescences with many corymbs, inflorescence axis with ferruginous pubescence, capsule oblate, compressed, dehiscing by 2 valves, but can be easily distinguished from the latter by the abaxial leaf blade and calyx densely ferruginous pubescent (vs. glabrous), petals light green (vs. yellowish-white), seeds 4–8 (vs. 2–4), filament 6–7 mm long (vs. 3–4 mm long).

Shrubs, evergreen, 2–4 m tall; branchlets densely ferruginous pubescent when young, old branchlets brown, lenticels inconspicuous. Leaves alternate; petiole 1–2 cm long, densely ferruginous pubescent; blades leathery, oblong or obovate-lanceolate, 5–12 cm long, 1.5–5 cm wide, apex mucronate or acuminate, base narrow cuneate, adaxially dark green, brown when dry, densely ferruginous pubescent when young, then glabrescent, abaxially densely ferruginous pubescent; midvein concave adaxially, prominent abaxially; lateral veins 6–8 pairs, conspicuous concave adaxially, prominent abaxially, curved arches meet up near the margin, reticulate veins distinct adaxially; margin entire, slightly reflexed after drying. Inflorescence paniculate, terminal, with many corymbs; primary peduncle 1–3 cm long, together with primary axis densely ferruginous pubescent; secondary peduncles vary in length, up to 3 cm long; corymbs 4–8-flowered; pedicels 2–4 mm long; bracts vary greatly in size and shape, ranging from leaf blade shape and size to slenderly linear or lanceolate, both surfaces densely ferruginous pubescent, deciduous in fruiting; bracteoles narrowly ovate, 2–4 mm long, ca. 1.5 mm wide, abaxially densely ferruginous pubescent, adaxially glabrous; sepals 5, free, or base slightly contiguous, ovate, 2–3 mm long, ca. 1.5 mm wide, abaxially ferruginous pubescent, adaxially glabrescent; petals 5, free, light green, 8–10 mm long, ca. 2 mm wide, both surfaces glabrous; stamens 5, nearly equal to petals in length, glabrous; filaments 6–7 mm long; anthers 1.5–2 mm long; ovary long ovate, densely ferruginous pubescent; placentas at the base of ovary; ovules 4–8; style 2–3 mm long, glabrous. Capsule suborbicular, slightly compressed, densely ferruginous pubescent, 8–12 mm in diam., dehiscing by 2 valves; pericarp thinly woody, horizontally numerous striate adaxially; seeds 4–8, subreniform, 4–5 mm long, 3–4 mm wide.

Phenology:— Pittosporum napoense was observed in flowering from March to May and in fruiting from July to October.

Etymology:— The specific epithet is derived from the type locality, Napo County of Guangxi, China. The Chinese name is given as “ Dz坡fiệ (pinyin: nà pō hǎi tǒng)”.

Distribution and ecology:— Thus far, Pittosporum napoense is only known from Napo County of Guangxi, China. It grows on limestone hills at an elevation from 900–1100 m. The slope direction is to the southwest or southeast and the slope gradient is ca. 60°. The tree layer is up to 8 m tall with a canopy cover of 75% and the shrub and herb layer covers are 70% and 20%, respectively. The associated plants include Pseudotsuga brevifolia W.C. Cheng & L.K. Fu ( Pinaceae ), Pistacia weinmanniifolia J. Poiss. ex Franch. ( Anacardiaceae ), Platycarya longipes Y.C. Wu ( Juglandaceae ), Acer sycopseoides F. Chun ( Sapindaceae ), Bonia saxatilis (L.C. Chia & al.) N.H. Xia ( Poaceae ), Pittosporum tonkinense Gagnep. ( Pittosporaceae ), Tetradium calcicola (Chun ex C.C. Huang) T.G. Hartley ( Rutaceae ), Polygala wattersii Hance ( Polygalaceae ), Myrsine kwangsiensis (E. Walker) Pipoly & C. Chen ( Primulaceae ), Phyllanthodendron dunnianum H. Lév. ( Phyllanthaceae ), Paraboea rufescens (Franch.) Burtt and Petrocodon coccineus (C.Y. Wu ex H.W. Li) Yin Z. Wang ( Gesneriaceae ), Microsorum cuspidatum (D. Don) Tagawa and Pyrrosia lingua (Thunb.) Farw. ( Polypodiaceae ), Pholidota yunnanensis Rolfe and Vanda concolor Blume ( Orchidaceae ), etc.

Conservation status:— Currently, Pittosporum napoense is only known from Napo County of Guangxi, China. It is expected to find more subpopulations in the neighboring areas having similar habitats to the type location. However, till now, only two subpopulations of P. napoense have been found after several field surveys conducted for more than ten years surrounding the limestone areas of Napo County, and a total of thirty individuals were found, including sixteen mature. Therefore, the population size of P. napoense is very small, and the Area of occupancy (AOO) is restricted. Based on the habitat survey data of subpopulations, the habitat quality and population size have a downward trend. The most important factor is deforestation by the local residents. According to Guidelines for Using the IUCN Red List Categories and Criteria ( IUCN 2024), P. napoense should be assessed as Critically Endangered (CR) based on criteria D ( IUCN 2012).

Additional specimens examined (paratypes):— CHINA. Guangxi Zhuang Autonomous Region: Baise City , Napo County, Baisheng Town , Nongmiao Village , elev. 1034 m, 14 May 2023, Y.L. Jiang & J.Q. Huang JYL2023051404 (IBK) ; the same location, elev. 1034 m, 14 May 2023, Y.L. Jiang & J.Q. Huang Y23051401 (IBK) ; the same location, 1 September 2023, C.Y. Zou, J.Q. Huang & L. Yang ZCY5001 (IBK) ; the same location, 25 March 2023, C.Y. Zou, J.Q. Huang & Z.C. Fan ZCY4108 (IBK) ; the same location, 22 October 2023, Y.L. Jiang Y23102202 (IBK) ; the same Town, Pojin Village, Tianfang Tun , 24 March 2012, Y.S. Huang & Y.B. Liao Y1071 (IBK) .

Notes:— Gowda (1951) informally separated the species from China and adjacent regions into two groups, Trivalvae and Bivalvae. Later, Chang & Yan (1979) formally named them at sectional rank as sect. Pittosporum and sect. Basiplacentum Chang & Yan (1979: 18), respectively. And Chang & Yan further divided sect. Basiplacentum into two series, ser. Umbelliferae Chang & Yan (1979: 18) and ser. Paniculiferae Chang & Yan (1979: 30). Accordingly, Pittosporum napoense belongs to sect. Basiplancentum ser. Paniculiferae .

Morphologically, P. napoense is closely related to P. kerrii , but differs by the characters of leaf blade, flowers and fruits. A detailed morphological comparison between P. napoense and P. kerrii is summarized in table 1. In the Chinese species of Pittosporum . P. parvilimbum Hung T. Chang & S. Z. Yan (1978: 88) , P. tonkinense Gagnep. (1908: 547) and P. fulvipilosum Hung T. Chang & S. Z. Yan (1978: 88) also have pubescent branchlet, inflorescence and fruit. P. parvilimbum can be easily distinguished from P. napoense by the characteristics of leaf blade small (3–5 cm long, 1– 1.7 cm wide) and glabrescent when old, lateral veins on both sides inconspicuous, petiole 3–5 cm long and glabrescent when old, inflorescences corymbose, bracts linear-lanceolate, 4–6 mm long, ovules ca. 16. P. fulvipilosum differs from P. napoense in both surfaces of leaf blade pubescent when young, glabrescent when old, lateral veins 10–12 pairs, reticulate veins indistinct adaxially, inflorescences corymbose, ovules 8–12, placentas slighty exserted in the middle part of valves. P. tonkinense differs from P. napoense in both surfaces of leaf blade glabrous, reticulate veins indistinct, inflorescences umbellate or racemose, peduncle very short, ovules ca. 4, capsule glabrescent or hairy.

The petal colour of the genus Pittosporum is usually yellow or white ( Gowda 1951). Since the morphological characteristics of the genus Pittosporum are highly heteroblastic, such as leaf size and shape, inflorescence and infructescence structure, etc., they will change due to the difference of habitats, or different growth periods ( Cayzer et al. 2023). The colour of petals also has such heteroblastism. For example, the petals of P. pauciflorum are usually white in the early stage of flowering, but will turn light yellow or yellow in the later stage of flowering, and there will also be differences among white, light yellow and yellow in different habitats. Based on the observation data of the flowers from the type locality at present, the petals of P. napoense are light green throughout the flowering period, which is an important distinguishing characteristic from most other species. However, whether the color varies with different habitats remains to be further observed.

In the genus Pittosporum , most species have unisexual flowers consisting of staminate flowers and pistillate flowers, especially in low-latitude island areas. However, this phenomenon is not common in high-latitude inland regions of East Asia. Based on the study of the species in China and India, all species, including 35 species and 6 varieties from China, are bisexual, and just a tendency for separation of sexes has been observed in few species ( Gowda 1951). Studies also have shown that the species in genus Pittosporum , and close relatives in the Apiales , are evolving from being functional dioecism to monoecism ( Schlessmann 2010, Schlessman et al. 2014). On the basis of the observation of the flower characteristics, it is found that all flowers of P. napoense are bisexual. Therefore, we speculate that the floral dimorphism of Pittosporum has significant differences in the inland areas and the island areas. This is an interesting phenomenon that need be further studied.