Sphaeropteris guangxiensis Y. F. Gu & Y. H. Yan

Sphaeropteris guangxiensis Y.F. Gu & Y.H. Yan (Figure 1)

Type:— China. Guangxi Province: Fangchenggang City, Dongxing County, Taohuaxi Village, 21°38′7″N, 107°41′22″E, 256 m, 01 May 2018. Morigengaowa & Jun-Jie Luo CFH09001402 (holotype, CSH! (CSH0155370); isotypes, PE!; paratypes, Morigengaowa & Jun-Jie Luo CFH09001403, Morigengaowa & Jun-Jie Luo CFH09001404, CFH09001405, and CFH09001406, CSH!)

Diagnosis:— Sphaeropteris guangxiensis is most similar to S. brunonina and S. hainanensis in terms of morphological characters of leaf, but the difference is that fiddleheads (young leaves spirally coiled in bud) of S. guangxiensis are densely scaly on the adaxial surface and few on the abaxial surface, fiddleheads of S. brunonina are fully scaly on both sides, and fiddleheads of S. hainanensis are not scaly (Figure 3 A ~C).

Description:— Trunk erect, approximately 10 m tall, up to 20 cm in diameter. Stipes warty at base, upper part and rachis smooth, yellowish to purplish. Lamina 2-pinnate-pinnatifid, up to 3 × 1.6 m, pinnae 20–30 pairs, ascending, lanceolate; largest pinnae up to 90 × 25 cm. Pinnules narrowly lanceolate, 9–14 × 1.8–2.5 cm, slightly narrowed at base, apex caudate, pinnatifid to pinnatisect; pinnule segments 13–22 pairs, falcate, wider at base, entirely or minutely crenate; veins 2- or 3-forked; abaxial side of pinnules glabrous, adaxial side glabrous or with sparse hairs; lamina glaucous abaxially; adaxial side of pinna rachis smooth or with pale antrorse hairs. Fiddleheads with thick scales at middle and brown hairs outside. Sori close to midveins of fertile pinnule segments, 5–8 pairs per segment, covering 3/4–5/6 segment; paraphyses pale to brown, filamentous, longer than or equal in length to sporangia; indusia absent. Spore granulate, thick, ca. 35- 45 μm in diam., polar view triangle, straight edge, equatorial view sector.

Distribution:— Sphaeropteris guangxiensis grows at the edges of forests. Present the new species is known only from the type locality.

Ecology:— The species was found associated with some woody plants (Figure 2: A, B), such as Mallotus japonicus (Sprengel 1826: 878) Müller Argoviensis (1865: 189), Mangifera indica Linnaeus (1753: 200), and Bambusa chungii McClure (1936: 639). It was also found to be associated with species of Arecaceae Bercht. & J. Presl, ferns such as Asplenium nidus Linnaeus (1753: 1079), Lemmaphyllum rostratum (Beddome 1866: 159) Tagawa (1966: 193), and Microsorum punctatum (Linnaeus 1763: 1524) Copeland (1929: 111) were found to be associated with their trunk. Approximately 50 adult plants and a few young ones were found in the population.

IUCN Red List category:— Sphaeropteris guangxiensis has a restricted geographic distribution, and yet not found in other regions out of the type locality. Local people occasionally utilize this species as firewood. Our field investigations showed that there were no abnormalities in the spores of the new species which indicated that the new species can replenish themselves. Moreover, we observed hundreds individuals of this species in a large population at the border of Guangxi Province, China and Vietnam. The status of the new species can be classified as Endangered (EN) [A2 a; B2 b(iv)(v)], but more investigations are still needed to accurately assess its conservation status.