Botanical Studies (2010) 51: 395-401.
systematics
Polystichum kungianum, sp. nov. (sect. Mastigopteris,
Dryopteridaceae) from Chongqing, China
Hai HE1 and Li-Bing ZHANG2,*
1Department of Biology, Chongqing Normal University, Shapingba, Chongqing 400047, P.R. China
2Chengdu Institute of Biology, Chinese Academy of Sciences, P.O. Box 416, Chengdu, Sichuan 610041, P.R. China and
 Missouri Botanical Garden, P.O. Box 299, St. Louis, Missouri 63166-0299, USA
(Received May 19, 2009; Accepted December 17, 2009)
ABSTRACT. A new fern species, Polystichum kungianum (sect. Mastigopteris, Dryopteridaceae), is described from Chongqing, China. The new species, occurring on limestone walls near a small karst cave, is the fourth species known so far in the section Mastigopteris. It is morphologically most similar to P. erosum, but its pinnae are deltate-lanceolate, and those below the middle of lamina are profoundly pinnatifid. It has an inconspicuous terminal bulbil at the apex of the rachis which never elongates, and its basal pair of pinnae is never reflexed. These differences are obviously distinct from P. erosum and make it clear that it could not merely be a variant population within that species, but must be a distinct species. Morphological and geographical features of the accepted species in sect. Mastigopteris are discussed, and a key to all four species is given.
Keywords: China; Chongqing; Dryopteridaceae; Karst flora; Polystichum kungianum; Polystichum sect. Mastigopteris; Taxonomy.

introduction
Worldwide tropical and subtropical karst landscapes are usually richer in vegetation type, plant species diversity, and endemism than other landscapes under similar climatic conditions (Furley and Newey, 1979). Karst landscapes are normally characterized by karst caves, which provide unique habitats for calcicole ferns. Not all available habitats of certain species are occupied by the same species, which suggests that some critical stage in their life cycle limited their colonization (Wild and Gagnon, 2005). Poor water holding capacity and frequent drought stress are the common hydrological features of limestone areas, while ferns are highly water-dependent in their sexual generation. This might result in a local scarcity of calcicole ferns, leading to their isolation and speciation.
The genus Polystichum Roth (Dryopteridaceae) is the species-richest fern genus in China, with 168 species documented in Flora reipublicae Popularis Sinicae, the Chinese version of Flora of China (Kung et al., 2001). Its species diversity is still not fully understood, especially in the underexplored mountainous hinterland in Southwest China with its extensive karst landscapes, where countless limestone caves of great variety offer particularly suitable habitats for the development of a fern flora rich in Polystichum (Wang, 1998). Further field investigations
*Corresponding author: E-mail: Libing.Zhang@mobot.org; Tel: +1-314-577-9454; Fax: +1-314-577-9596.
often lead to the discovery of new taxa. In Guizhou Province alone, one of the most karst-dominant regions in Southwest China, more than ten species have recently been described or found new to science (Wang and Wang, 2001;
Wang and Wang, 2003; Luo, 2009; Zhang and He, 2009a,
b; 2010; Zhang et al., 2010). These new species are mostly endemic to karst areas, occurring in habitats of limestone crevices or cave mouths with twilight conditions. It may be noted that most of these species have very small population sizes.
During field work on polystichoid ferns in Chongqing, Southwest China, in 2008, a species of Polystichum, which looks, at first glance, like a species of Woodsia and occurs on limestone walls, was found to be distinctive. It shares some similarities with species in sect. Mastigopteris Tagawa (1940) in its habit, scale types, and most importantly the terminal bulbil at the apex of rachis. However it is significantly morphologically different from any known species in the genus Polystichum. Therefore it is described below as P. kungianum H. He & L. B. Zhang and grouped in sect. Mastigopteris.
material and methods
The morphological data are based on the voucher specimens: CHINA. Chongqing: Wuxi, H. He & Y. Q. Yang 791 (CTC, MO), see below. Morphological measurement of roots, petiole, rachis, scales and indusia was conducted with a micrometer under a microscope.
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taxonomic treatment and results
The new species is described as follows:
Polystichum kungianum H. He & L. B. Zhang, sp. nov. -TYPE: CHINA. Chongqing: Wuxi County, Wenfeng Town, Hongchiba, 31°32.47' N, 108°03.80' E, on moist limestone walls at the edge of a small karst cave, alt. 1,750 m, 17 July 2008, H. He & Y. Q. Yang 791 (HOLOTYPE: CTC; ISOTYPES: CDBI, CTC, HAST, MO).憲需耳蕨 Figures 1, 2
Species affinis P. eroso Ching & Shing, sed pinnis aliquot parium inferiorum profunde pinnatifidis, lobis paris proximi fere liberis, rachi infra gemmam minimam instructa apicis haud prolongata, pinnis deltoideo-lanceolatis, omnibus patentibus et vix deflexis a quo differt.
Plant perennial, evergreen, 12-16 cm tall. Rhizome 0.5­2.0 cm long, 2-3 mm in diam., up to 1.5 cm in diam. with base of remnant old petioles, erect or slightly prostrate; scales linear-lanceolate, c. 3.0 x 0.8 mm, dull brown, margin subentire; roots up to 10 cm long, 3-4 mm in diam. Fronds caespitose; petiole 1.5-4.5 cm long, 1-2 mm in diam. at middle, adaxially canaliculate, stramineous; scales on basal petiole narrowly deltoid-lanceolate, 3-4 x 0.3­1.2 mm, thin chartaceous, brown, apex filiform, margin at base with outgrowth, outgrowth hair-like, tortuose and soft, margin upward sparsely fimbriate or nearly entire; scales on distal petiole similar but narrower, mostly linear-lanceolate, up to 3 x 0.5 mm, thin chartaceous, brown, apex filiform. Lamina lanceolate, 5.5-12.5 x 1.5-2.5 cm, acuminate towards the apex, slightly narrower at the base; rachis 0.5-1.2 mm in diam. about its middle, apex with a small proliferous bulbil, with no flagelliform prolongation; 1-pinnate-pinnatifid. Pinnae 18-22 pairs, 0.5-1.5 x 0.3-0.6(-0.8) cm, shortly petiolate, alternate, lower pairs deltate-lanceolate, attached almost at right angles to the rachis, upper pairs shorter and rhombic-lanceolate, spreading to slightly ascending, acroscopic base auriculate, basiscopic base cuneate, apex acute and terminating in a mucronate spine, several pairs of pinnae below the middle of the lamina deeply pinnatifid with their proximal pair of lobes nearly free, pairs above the middle serrate at their margin with a mucronate tip at tooth apex and basal acroscopic auricle deltate; lobes obliquely oblong to obovate, mucronate at apex, margin entire; texture chartaceous, adaxial surface slightly yellowish green and with occasional articulate hairs especially along midrib, abaxial surface only slightly paler and moderately clothed with scattered microscales; microscales linear-subulate, up to 2.5 mm long, brown, usually with a few curly hair-like outgrowth at the margin of their broader base; venation pinnate, obvious abaxially, lateral veins free, 1-2 times forked. Sori terminal on distal branchlets of forked veinlets, 0.5-2.5 mm apart (when young), (1-)3-5(-6) in one row on each side of midrib, submarginal; indusia peltate, irregularly lacerate at the margin, membranaceous, white when young, glossy brown later, adjacent ones often overlapping by 0.5-1.5 mm and extending over the pinna
margins when mature. Spores not seen.
Morphological Distinctiveness. Polystichum kungianum has a similar stature and lacerate indusia to P. erosum, but the pinnae below middle of the lamina of the former are profoundly pinnatifid with the proximal pair of lobes almost free from the other parts. Basal and adjacent pairs of pinnae of P. kungianum are attached almost at right angles to rachis, whereas they are usually more or less reflexed in P. erosum. Most importantly, P. kungianum has deltate-lanceolate pinnae and a rather small terminal bulbil borne directly on the foliose apex of the rachis which never elongates, while P. erosum has a much bigger terminal bulbil on the rachis which usually elongates between the terminal bulbil and the uppermost foliose part.
Geographical Distribution. This species is only known from the type locality in Hongchiba National Forest Park, Wuxi County, Chongqing, China. This area is located in a series of parallel ridge-valley regions in the southern part of Dabashan Mountain bordering Shaanxi Province. It is assumed that the new species might also occur in neighboring counties of Wuxi in Chongqing and/or Shaanxi in similar habitats.
Ecology. The new species occurs on shady moist limestone walls at the edge of a small northeast-facing downward sloping karst cave, which is located at the foot of a gradual mountain slope at the southern margin of a narrow area of flat land, extending from the northwest to the southeast at 1,750 m. alt.
It is accompanied by Adiantum wattii Baker mixed together in a mat of mosses and liverworts. On the ground and around the cave mouth, there are Ligularia hodgsonii Hook. f., Matteuccia orientalis (Hook.) Trevis., Neillia sinensis Oliv., Rubus mesogaeus Focke ex Diels, Sinacalia tangutica (Maxim.) B. Nord., Sorbaria arborea Schneider, Spiraea japonica L. f., and unidentified species of Corydalis, Cotoneaster, Elatostema, Heracleum, Impatiens, Salix, etc. The mountain slope is covered with interspersed patches of secondary deciduous shrubs and broadleaf forests, characterized by Betula albosinensis Burkill, Corylus heterophylla Fisch. ex Bess. var. sutchuensis Franch., Populus lasiocarpa Oliv., Salix fargesii Burkill, and Toxicodendron vernicifluum (Stokes) F. A. Barkley among others. Grasses and forbs dominate the flat land with swamps in between supporting species of Eleocharis, Fimbristylis, Juncus, etc. It has been reported that the flat land was the result of a geological upheaval and filling-up of an inland lake (Chen et al., 1994).
Conservation Assessments. Less than 50 individuals of the new fern are scattered on the limestone walls over an area of less than 3 m2 and c. 1.5 m below to 1 m above the horizontal surface of the flat land. The new species should clearly be classified as CE ―Critically Endangered― following the IUCN (The International Union for Conservation of Nature and Natural Resources) guidelines (IUCN, 2008). Hongchiba National Forest Park, where the new species was discovered, has been established since 2002.
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Figure 1. Polystichum kungianum. A, Habit; B, Pinna; C, Scale from base of stipe; D, Rachis scale; E, Microscales; F, Indusium. (based on an isotype H. He & Y. Q. Yang 791, MO).
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Figure 2. Polystichum kungianum. A, Habitat with two individuals (arrows inset) accompanied by Adiantum wattii; B-C, Plants showing habit; D, Portion of lamina of a mature leaf; E, Geographical distribution (•) in northeastern Chongqing, China.

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Etymology. We name this species Polystichum kungianum in honor of the late Professor Hsian-Shiu Kung (Xian-Xu Kong) of the Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, for his long and dedicated study of the fern diversity of Chongqing and Sichuan, China. He was the volume editor of Flora Reipublicae Popularis Sinicae vol. 5(2) (Kung et al., 2001) and one of the major contributors of the treatment of Polystichum in this flora as well as the author of Flora Sichuanica vol. 6 (Pteridophytes) which documents the lycophytes and about half of the fern species in Chongqing and Sichuan (Kung, 1988). The second author of this paper earned his M.Sc. under him and started his career as a pteridologist in his laboratory.
discussion
The section Mastigopteris Tagawa in Polystichum contains a small group of species characterized by their 1-pinnate lamina, prolonged rachis with a proliferous bulbil at its apex, narrow scales with hairy outgrowths on their lower margins, sori terminal on distal branchlets of the forked lateral veins, arranged in straight rows and often only in the acroscopic half of the pinna, and indusia large and persistent (Tagawa, 1940; Daigobo, 1972; Wu
and Ching, 1991; Kung et al., 2001). A terminal bulbil
at the apex of the rachis is a unique feature of Sect. Mastigopteris, and other species in the same genus either have no bulbil at all or have a bulbil on other parts of the rachis, usually subapically. As for the reproductive ability of the terminal bulbil, rooting and sprouting leaves were only occasionally found both in the field and in herbaria and most often in P. craspedosorum (Maxim.) Diels, another member of sect. Mastigopteris. The length of prolonged rachis in between the terminal bulbil and the foliose part varies considerably, from almost no elongation to more than 10 cm (flagelliform). The scales on the stipe (petiole) and rachis and microscales on the abaxial surface of the pinnae especially along the veins in this section are very uniform with some minor modifications in shape and size. However, scale-density varies greatly among different populations and individuals, and field observation found that senescence leads to detachment and loss of the partly deciduous scales. Considering the characters of sect. Mastigopteris described above, the new fern, P. kungianum, undoubtedly falls into this section morphologically.
Of the four species, including P. kungianum, placed in sect. Mastigopteris, P. craspedosorum is the most variable in size and form, within which several infraspecific taxa have been proposed based on certain morphological characters (Maximowicz, 1870; Baroni
and Christ, 1897; Makino, 1912). It should be mentioned
that P. craspedosorum var. giraldii Baroni & Christ was reported to have no elongated rachis below the terminal bulbil and P. craspedosorum var. dissectum Makino to have pinnatifid pinnae resembling P. kungianum. Under
certain circumstances individuals of P. craspedosorum may have some leaves without elongated flagelliform rachides or rarely even without a terminal bulbil (as in some specimens collected in a karst cave in Guizhou, L. B. Zhang, H. He, & C. B. Jiang 729, CDBI, CTC, MO), but an elongated flagelliform rachis terminating in a rooting bud was also found in leaves of the same individual plant. Both P. craspedosorum and P. shandongense J. X. Li & Y Wei usually have entire indusia (Li et al., 1984; Kung et al., 2001). Some plants found on limestone walls in southern Chongqing with crenulate margined indusia, coarsely serrated pinnae, and relatively larger size (but smaller than in P. shandongense) correspond with P. leucochlamys Christ (1911), which is treated as a synonym of P. craspedosorum (Tagawa, 1940; Nakaike, 1975). Plants of both P. erosum and P. kungianum have lacerated or erose margined indusia, and they both have a seldom rooting terminal bulbil with a relatively shorter elongated rachis or without elongation at all.
Geographically, sect. Mastigopteris as a whole is distributed in eastern Asia, including China, the Korean Peninsula, Japan, and southeastern Siberia of Russia. The most widely distributed species is P. craspedosorum, occurring in all the areas mentioned for the section. Concerning its wide distribution, we still think it is reasonable to identify plants corresponding to P. leucochlamys as belonging to P. craspedosorum, but further investigation might justify its separation. Polystichum shandongense is endemic to three counties in Shandong and one county in Liaoning provinces (Li et al., 1984; Kung et al., 2001). Though P. erosum was formerly reported as endemic to Sichuan (common in Mt. Emei) and the southern slopes of Qinling (Ching, 1964; Anonymous, 1974), later explorations found it scattered in the provinces of Yunnan, Guizhou, Sichuan, southern Gansu, southern Shaanxi, western Hubei and western
Hunan (Wu, 1992; Wang and Wang, 2001; Kung et al.,
2001; Lu, 2005; Guo et al., 2008). So far, P. kungianum has only been discovered in northeastern Chongqing. With few exceptions, plants of sect. Mastigopteris grow on rocks or crevices, and they are most often found in karst areas on limestone walls in Southwest China (see Wu,
1992; Lu, 2005; Guo et al., 2008).
The four members of sect. Mastigopteris can be distinguished from one another by the following key:
Key to Polystichum craspedosorum and its allies in sect. Mastigopteris
1. Indusia entire or rarely minutely crenate at the margin; rachis often with an obvious flagelliform prolongation below the proliferous terminal bulbil.
2. Pinnae oblong or deltate-lanceolate, shorter than 2
cm; scales on stipe base lanceolate ..............................
......................................................... P. craspedosorum
2. Pinnae lanceolate, 2-2.5 cm long; scales on stipe base narrowly ovate .................................. P. shandongense
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1. Indusia erose or lacerate at the margin; rachis shortly or not elongated below the mostly smaller terminal bulbil.
3. Lamina 1-pinnate; pinnae oblong or oblong-lanceolate, obviously serrate at the margin; basal pairs of pinnae often reflexed; rachis more or less with a
non-foliose elongation below the terminal bulbil .........
....................................................................... P. erosum
3. Lamina 1-pinnate-pinnatifid; pinnae deltate-lanceolate, pairs above the middle serrate at their margin, lower pairs of pinnae profoundly pinnatifid with proximal pair of lobes nearly free; pinnae spreading or slightly ascending; rachis never
elongated below rather small terminal bulbil...............
................................................................ P. kungianum
Acknowledgements. This project was partly supported by research funding from Chongqing Normal University (07XLB001) and Chongqing Education Commission
(KJ090827) to HH and by funding from the Open
Laboratory of Ecological Restoration and Biodiversity Conservation of Chengdu Institute of Biology, Chinese Academy of Sciences, to LBZ. Youqing Yang and Tailong Huang helped during the field work. Musen Guo prepared the basic line drawing. Helpful comments were received from C. R. Fraser-Jenkins, Peishan Wang, and George Yatskievych. The curators of the herbaria CDBI, CTC, and MO are thanked for giving access to the material in their care.
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中國重慶石灰巖地區耳蕨屬邊果耳蕨組新種:憲需耳蕨
何海 1張麗兵2
1重慶師範大學生物繫 (CTC)
2中國科學院成都生物研究所 (CDBI); 密蘇奡茠奎 (MO)
本文描述了在中國重慶發現的耳蕨屬邊果耳蕨組(Polystichum sect. Mastigopteris) 一新種:憲需耳蕨
(P. kungiamum),並提供線繪圖與彩色照片以資辨識。該新種生於一個小型岩溶洞穴邊緣石灰岩壁上,是
耳蕨屬邊果耳蕨組中迄今發現的第4個種。憲需耳蕨與蝕蓋耳蕨(P. erosw/m )最接近,但其葉片中部以
下多對羽片深羽裂,葉軸頂端較小而不明顯的芽胞之下無伸長的葉軸,羽片三角狀披針形,下部羽片平
展而從不向下反折斜展等特徵可以區別。文中還討論了邊果耳蕨組已知種類的形態變化、地理分佈和生
境等特徵並編制了這4個種的檢索表。
關鍵詞:中國;重慶;鱗毛蕨科;喀斯特植物;憲需耳蕨;邊果耳蕨組;分類。