Selaginella wangpeishanii Li Bing Zhang, H. He & Q. W. Sun, 2014

Selaginella wangpeishanii Li Bing Zhang, H. He & Q. W. Sun View in CoL , sp. nov. Fig. 1 View FIGURE 1 .

Type:— CHINA. Guizhou Province: Libo Co., Jiarong Zhen, close to Henggu Cun , 25°27.4235’N, 108°07.6417’E, 670 m, on weathered crust of limestone rocks at the opening of a limestone cave, 24 October 2012, Li-Bing Zhang & Hai He 6234 (holotype CDBI! GoogleMaps , isotypes CTC GoogleMaps , GZTM GoogleMaps , MO GoogleMaps , Herb. Pei-Shan Wang GoogleMaps ).

Selaginella wangpeishanii is similar to S. gebaueriana Handel-Mazzetti (1929: 9) , but the former is far smaller and its lateral trophophylls have only serrulate margins. In addition, it bears relatively shorter strobili, some of which with unusual development of vegetative shoots from apices.

Plants epilithic, 7–12 cm long. Stems prostrate, 4–5 mm wide including microphylls, sparsely (1–3 times) dichotomously branched. Main stems branched throughout, stramineous, ca. 0.5 mm diameter in mid-portion, terete, slightly sulcate. Lateral branches 8 to 11, 1-pinnate or dichotomous, branchlets 1.0– 2.5 cm apart from each other. Ultimate branches 2–3 mm wide including trophophylls. Rhizophores borne throughout and 1–4 times dichotomously branched. Trophophylls trimorphous: lateral trophophylls patent, obliquely ovate, 1.8–2.3 × 0.9–1.6 mm, rounded basally, acute or mucronate apically, margins serrulate or partially nearly entire; median trophophylls pointing upward, ovate, 0.8–1.1 mm long excluding apical arista, 0.4–0.7 mm wide, slightly cordate basally, asymmetrical, base forming small round auricle, apex with long arista of ca. 0.5 mm, margins notably serrulate or shortly ciliate; axillary trophophylls ovate to narrowly ovate, 1.0–1.3 × 0.5–0.8 mm, rounded basally, acute or more or less blunt apically, margins very sparsely serrulate or partially subentire. Strobili compact, dorsiventrally complanate, solitary or paired (forked), on terminal or lateral stems, 3.0– 5.5 mm long. Sporophylls monomorphic, narrowly ovate or ovate-lanceolate, 1.2–1.5 × 0.5–0.6 mm, keeled, basally rounded, apically acuminate, margins shortly ciliate. Microphylls with very narrow, sometimes indiscernible, differentiated white margins. Spores immature; macrospores 4 in each macrosporangium, yellowish; microspores not seen.

Distribution and habitat:— Selaginella wangpeishanii is currently known only from Libo County in southern Guizhou, China. It is possible that this species also occurs in adjacent similar areas in southern Guizhou. Selaginella wangpeishanii was collected from weathered crust of limestone rocks inside a limesone cave, at an elevation of ca. 670 m. The soil at the type location was of basic pH.

IUCN Red List category:— Only one population at a single locality on Libo County with an area of occurrence less than 5 m 2. Owing to the interweaving of branches, it is difficult to figure out the number of individuals. The habitat of Selaginella wangpeishanii in Libo County is adjacent to, but not inside the National Maolan Nature Reserve. There was no protection measure taken to conserve the habitat. Based on the evidence available, it is much better to classify S. wangpeishanii as Critically Endangered or CR, following The International Union for Conservation of Nature and Natural Resources guidelines (IUCN, 2008), but further investigations are necessary to clarify its status of conservative importance.

Etymology:— Selaginella wangpeishanii is named in honor of Professor Peishan Wang of the Guizhou Institute of Biology, Guizhou Academy of Sciences, Guiyang, for his long and dedicated study of the lycophye and fern diversity of Guizhou, China. He is also one of the only few specialists of Selaginella in China.

Discussion:— Morphologically, Selaginella wangpeishanii is most similar to S. gebaueriana in its monomorphic and narrowly ovate or ovate-laceolate sporophylls, but the former is only up to 12 cm long and the margins of its lateral trophophylls have only serrulations ( Fig. 1D, E, F View FIGURE 1 ), whereas the latter is up to 60 cm long and has cilia on the margins of its lateral trophophylls ( Tab. 1 View TABLE 1 ). Also, the former is found only at low elevations (670 m) whereas the latter occurs at elevations between (800–)1000 and 2400 m ( Chu 2006). Selaginella wangpeishanii is also similar to S. davidii Franchet (1884: 344) , from which it differs by shortly ciliate margins of both sporophylls and median tropophylls ( Fig. 1G View FIGURE 1 ), and its microphylls with relatively narrower or even unnoticeable white margins. Besides, S. wangpeishanii occurs in southern Guizhou in southwestern China, whereas S. davidii is found almost exclusively in northern China (see below). Selaginella wangpeishanii has strobili up to 5.5 mm long, whereas S. gebaueriana and S. davidii have strobili up to 18 mm and 11 mm long, respectively ( Wang & Wang 2001, Zhang 2004, Chu 2006).

Interestingly, Alston (1934: 274) synonymized Selaginella gebaueriana with S. davidii . This was followed by Zhang et al. (2013: 38). Zhang (2004: 149–153) treated them as two subspecies of S. davidii , while other botanists treated them as separate species (e.g., Kung 1981: 254, 1988: 65; Wang 1990: 269; Wang & Wang 2001: 632; Chu 2006: 65). Morphologically, S. gebaueriana is up to 60 cm long and has ciliate microphylls, while S. davidii is shorter than 45 cm and has serrulate microphylls. In addition, S. gebaueriana occurs in southwestern China and adjacent regions, i.e., Chongqing, western Guangxi, Guizhou, western Hubei, western Hunan, Sichuan, Xizang, and Yunnan, while S. davidii is mainly distributed in northern China, i.e., Anhui, Gansu, Hebei, Henan, Ningxia, Shaanxi, Shandong, and Shanxi.

Notably, some ultimate branches of Selaginella wangpeishanii bear microphylls in ascending order of trophophylls, sporophylls or sporophyll-like microphylls, and trophophylls (hereafter termed as TST arrangement of microphylls; Fig. 1H View FIGURE 1 ), a phenomenon never previously observed in species of Selaginella in China. The sporophyll-like microphylls are morphologically similar to sporophylls in their shape, size, and arrangement, though with no sporangia at their axils. It is possible that they are sporophylls of previous seasons with sporangia fallen off. However, whether this is just aberrant growth of some of the individuals or an adaptive advantage for specific cave habitat of this species is pending for clarification. See Table 1 View TABLE 1 for a comparison of these three morphologically close species.

Following Jermy (1990), Selaginella wangpeishanii can be assigned to S. subg. Stachygynandrum . Due to the polyphyly of this subgenus ( Korall & Kenrick 2002), only future molecular analysis can reveal the true systematic relationship of the new species.