Botanical Studies (2010) 51: 99-106.
SYSTEMATICS
Two new species of Hypodematium (Hypodematiaceae) from limestone areas in Guangdong, China
Fa-Guo WANG, Dong-Ming LIU, and Fu-Wu XING*
South China Botanical Garden, Chinese Academy of Sciences, 723 Xingke Road, Tianhe District, Guangzhou 510650, P.R. China
(Received June 25, 2008; Accepted June 18, 2009)
ABSTRACT. Hypodematium humile F. G. Wang & F. W. Xing and H. villosum F. G. Wang & F. W. Xing, two new species of Hypodematiaceae from Guangdong, southern China, are described and illustrated. Their spore morphology, ecology and conservation status are also presented. Hypodematium villosum differs from H. fordii in having glabrous petiole except on the base, both surfaces of lamina, rachis and costa densely covered with long acicular hairs ca. 1 mm long, and apex of pinnulets acute. Hypodematium humile differs from H. glandulosum in having leaves 8-11 cm long with both surfaces of lamina, rachis and costa sparsely covered with rod-shaped glandular hairs and caducous indusium. A key to the species of Hypodematium known from Guangdong Province is provided. The systematic relationship of Hypodematium with Leucostegia is also discussed.
Keywords: China; Endemism; Guangdong; Hypodematium humile; Hypodematium villosum; Limestone; New species; Rare plant; Spore morphology.
INTRODUCTION
Described in 1833, Hypodematium Kunze is the only genus of the Hypodematiaceae. Iwatsuki (1964) reviewed the genus and recognized four species including one subspecies. More recently, over 1 8 species of Hypodematium, mainly distributed in subtropical and temperate areas of Asia and Africa, have been described (Shing et al., 1999; Tsai and Shieh, 1994). China, with 14 species and one variety of Hypodematium, is regarded as the center of distribution of this genus. Hypodematium is a unique fern genus, because it grows on soils derived from limestone rocks and has distinctive swollen scaly base of stipe and indusium. Hypodematium is closely related to Cystopteris and some authors consider it to be a distinct section of this (Ching, 1935). Due to its unique morphology (Iwatsuki, 1964), Hypodematium has been placed in different suprageneric taxa, e.g. Athyriaceae (Woodsiaceae), Dryopteridaceae, and Thelypteridaceae.
During a field-trip to the limestone area of Guangdong Province (southern China), we collected some specimens of Hypodematium that we were unable to assign to any of the previously described taxa. Thus, they are described here as two new species.
MATERIAL AND METHODS
Herbarium materials for morphological study were obtained from PE, IBSC and SYS. Some taxa were studied during our field-trios expeditions to Guangdong in 2005 and 2008. For the SEM studies, spores were placed on aluminum stubs with double-sided tape and sputter-coated with gold. Spores were observed and photographed under a Hitachi JSM-6360LV scanning electron microscope.
Morphological observations and measurements on collections were made with a ruler or binocular light microscope fitted with an eyepiece graticule. Only mature plant parts were measured. Details of plant growth habit and size, colour of fresh leaves and scales, and information on the habitat and locality were taken from the collector' s notes recorded on the herbarium label and from our field observations.
The mature spores were put in a centrifuge tube, 70% ethanol was added, and spores shaken with an ultrasonic wave bath for 10 min. After 4 min in an Eppendorf centrifuge, they were thrice washed with 70% ethanol and thrice shaken with an ultrasonic wave bath for 10 min after a liquid exchange each time. Finally, the spores and ethanol were moved to double-sided adhesive tape with Eppendorf. They were then treated by dessication and spray-gold when ethanol volatilized, and SEM was used to study their microstructure.
*Corresponding author: E-mail: xinfw@scib.ac.cn; Tel: +86-20-37252557; Fax: +86-20-37252831.
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NEW SPECIES
1. Hypodematium villosum F. G. Wang & F. W. Xing, sp. nov. ―TYPE: CHINA. Guangdong Province: Meizhou City, Jiaoling County, Xingfu Town, Changlong Village, limestone mountain, altitude 50 m, 15 Nov 2005, Faguo Wang et al. 1251. (Holotype: IBSC).毛葉腫足蕨
Figure 1
Species affinis H. fordii, sed petiolo praeter basim glabro, lamina 25-30 cm longa basi 35-40 cm lata, lamina utrinque, rhachi et costa villis acicularibus densis
obtectis, pinnis 12-15-jugatis, lobis acutis, margine villis acicularibus densis obtectis. Affinis H. microlepioidi, sed lamina quadripinnata, petiolo pinnae ca. 1.5 cm longo, lobis acutis integris, pinnis utrinque sine squamis differt.
Plants slender, 50-65 cm tall; rhizomes short-creeping, covered with scales; scales reddish-brown, narrowly lanceolate, 0.6-1 cm long, ca. 1 mm broad near the base, membranaceous, lucid. Leaves close together; petiole 25 -30 cm long, ca. 1 mm in diameter, stramineous, covered with scales the same to the rhizome, glabrous upward; lamina 25-30 cm long, base 35-40 cm broad,
Figure 1. Hypodematium villosum F. G. Wang & F. W. Xing. A, Habit; B, Rhizome and lower portion of petiole; C, Abaxial view of portion of pinnule rachis with pinnulet; D, Adaxial view of portion of pinnule rachis with pinnulet; E, Scale from rhizome; F, Hair from lamina; G, Sori; H, Sporangia. Drawn from Wang Faguo et al. 1251 (IBSC).
WANG et al. ― Two new species of Hypodematium
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ovate-quinquangular, apex acuminate and pinnatifid, quadripinnate, tripinnate upward; pinnae 12-15 pairs, basal two pairs sub-opposite, alternate upward, oblique, first basiscopic pair enlarged, 5-6 cm apart from upper one, 16-20 cm long, 6-8 cm broad at the base, triangular-ovate, apex acuminate, with petiole ca. 1.5 cm long, tripinnate; pinnules ca. 12 pairs, alternate, anadromous, oblique, close together, basiscopic pinnule bigger than acroscopic ones; secondary pinnules 8-10 pairs, alternate, first basal
pairs opposite and enlarged, ca. 4 cm long, base decurrent with narrow wing, pinnate; third pinnules ca. 6 pairs, apex acute, base decurrent, margin lobed to 1/2; pinnulets 3-4 pairs, apex acute, entire, margin densely covered with long acicular hairs; veins prominent abaxially, veinlet simple, 1-2 on each lobes, ending in margin. Lamina papyraceous, virescent when dry, densely covered with gray long acicular hairs ca. 1 mm long, especially on the rachis and costa. Sori small, dorsiferous on the middle of veinlet,
Figure 2. SEM photographs of Hypodematium spores. A-B, Hypodematium villosum (spore from F. G. Wang 1251. A, x1,500, scale bar 10 |im; B, x6,000, scale bar 2 |im); C-D, Hypodematium humile (spore from F. G. Wang 1255. C, x1,600, scale bar 10 ^m; D, x 8,500, Scale bar 2 |im); E-F, Leucostegia immersa (Spore from J. S. Xin 626 (PE), E, x1,800, scale bar 10 |im; F, x5,000, scale bar 5 阿)■
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one on each lobe; indusium rounded nephroid, grayish, membranaceous, densely covered with long acicular hairs, persistent; spore monolete, perispore psilate, with some granular ornamentation.
Ecology. Hypodematium villosum is a calcicolous fern that attachs to rocky tunnels on limestone mountain in Fung Shui Wood near a village. Plants were collected in association with Ctenitopsis devexa (Kunze ex Mett.) Ching & Chu H. Wang, Pteris plumbea H. Christ, P. deltodon Baker, Pterolobium punctatum Hemsl., and Alocasia macrorrhiza Schott.
Distribution. Hypodematium villosum is endemic to Changlong village, Xingfu Town, Jiaoling County, eastern Guangdong, southern China (Figure 4).
Conservation status. Hypodematium villosum is only known in a single locality and has a very small population size. Therefore, it has a Critically Endangered (CR) designation according to the IUCN (2001).
Etymology. Named from the Latin word 'vi〃os謹，， referring to the long acicular hairs on the lamina that distinguish other species of Hypodematium except H. microlepioides.
Spore morphology. Light microscope observation showed the spore of Hypodematium is eudipleural and monolete, and the corrugation of the perispore is striate, reticulate or circinate (Zhang et al., 1976). Scanning electron microscope observation found the spore of Hypodematium villosum to be monolete and the perispore psilate with some granular ornamentation (Figure 2).
Figure 3. Hypodematium humile F. G. Wang & F. W. Xing. A, Habit; B, Abaxial view of portion of pinnule rachis with pinnulet; C, Glandular hair from lamina; D, Sori; E, Sporangia; F, Scale from rhizome. Drawn from Wang Faguo et al. 1255 (IBSC).
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Figure 4. Distribution of Hypodematium villosum (black square) and H. humile (black triangle) in Guangdong, China. (from Yan, 2004).
However, the perispores of the related species H. fordii and H. microlepioides are circinate and striate, respectively
(Zhang et al., 1976).
Spore surface is unclearly observed of contaminated small spores collected from herbarium specimens. After being soaked in 70% ethanol and shaken in the ultrasonic wave bath, the treated spore surface becomes clearer than untreated ones under SEM. This method is easy to carry out and obviously more effective than routine procedures.
Morphological notes. Hypodematium villosum can be differentiated from other species of Hypodematium by its slender individual plants, long acicular hairs and small sori on the lamina. It resembles H. fordii (Shing et al., 1999), which is distributed in Guangdong, Guangxi, Fujian, and Anhui Provinces of China and Japan, although H. villosum plants have a more slender texture. However, the former
differs primarily as follows: petiole glabrous except the base, lamina 25-30 cm long, base 35-40 cm wide, surfaces of lamina, rachis and costa densely covered with long acicular hairs ca. 1 mm long; pinna 12-15 pairs; apex of pinnulets acute, margin densely covered with long acicular hairs, and perispore psilate.
Hypode m atiu m villosu m als o res embles H. microlepioides (Shing et al., 1999), a plant endemic to Yunnan Province in China. Both species have glabrous petiole, and the rachis and costa of both are densely covered with long, grayish acicular hairs. However, the latter differs from H. villosum in having the lamina 3-pinnate; the pinnule sessile; the pinnulet oblong, and the apex with 2-4 teeth; both surfaces of pinna have rufous and narrowly lanceolate scales. A morphological comparison between Hypodematium villosum, H. fordii
Table 1. Diagnostic characters among Hypodematium villosum, H.fordii and H. crenatum.
Characters
H. villosum
H. fordii
H. microlepioides
Petiole
Glabrous upside the base
Sparsely covered with rod-shaped
Glabrous upside the base
glandular hairs upside the base
Lamina
25-30 x 35-40 cm, densely
15-20 x 12-18 cm, sparsely
12-18 x 9-12 cm, densely covered with
covered with gray long acicular
covered with rod-shaped
gray long acicular hairs ca. 0.8 mm
hairs ca. 1 mm long
glandular hairs
long and few rufous scales
Rachis and costa
Densely covered with gray long
Sparsely covered with rod-shaped
Densely covered with gray long
acicular hairs
glandular hairs
acicular hairs and few rufous scales
Pinna
12-15 pairs, with petiole ca. 1.5
8-10 pairs, with petiole 2-3 mm
8-12 pairs, sessile
cm long
long
Pinnulet
Apex acute, margin densely
Apex acute, margin without hairs
Apex oblong, with 2-4 teeth, margin
covered with gray long acicular
without hairs
hairs
Spore
Perispore psilate
Perispore circinate
Perispore striate
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and H. crenatum is given in Table 1.
2. Hypodematium humile F. G. Wang & F. W. Xing, sp. nov. ―TYPE: CHINA. Guangdong Province: Meizhou City, Jiaoling County, Xinpu Town, Youkeng Village, Xianyan temple, limestone mountain, altitude 100 m,
15 xi. 2005, Faguo Wang et al. 1255. (holotype: IBSC).
矮腫足蕨 Figure 3
Species affinis H. glanduloso, sed foliis 8-11 cm longis, squamis 0.4-0.6 cm longis, petiolo c. 0.5 mm diametro, pinnis praeter eas basiscopicas sessilibus, lamina, rhachi et costa pilis sparsis bacillaribus glandiferis obtectis, pinnulis apice obtusis, indusiis caducis differt.
Plants 8- 1 1 cm tall; rhizome short, suberect, covered with scales; scale ca. 0.9 cm long, reddish-brown, narrowly lanceolate, apex acuminate, glabrous, membranaceous. Leaves 1 or 2, petiole 4-5 cm long, ca. 0.5 mm in diameter, stramineous, base and middle glabrous, sparsely covered with rod-shaped lemon-yellow glandular hairs upward; lamina 4.5-5.5 cm long, base 5-7 cm wide, ovate-quinquangular, apex acuminate and pinnatifid, base rounded cordate, tripinnate; pinnae 6-7 pairs, slightly oblique, basal 1-4 pairs subopposite, 0.4-1.2 cm apart, alternate upward, first basiscopic pair enlarged, 2.5-3.5 cm long, base 2-2.5 cm wide, triangular-ovate, apex obtuse, base cordate, with petiole c. 3 mm, bipinnate; pinnule 4-5 pairs, anadromous, alternate, slightly oblique, close together each other, basiscopic pinnule bigger than acroscopic ones, oblique, close together; first basal pairs of secondary pinnules opposite and enlarged, 1-1.1 cm long, base c. 1 cm wide, triangular-ovate, apex obtuse, base nearly truncate, decurrent to short petiole with narrow wing, pinnate; secondary pinnule 3-5 mm long, base c. 3 mm wide, triangular-ovate, apex obtuse, base connate with costa more or less, pinnatifid; pinnulet nearly trapeziform, apex obtuse, entire; other pairs of pinnae shorten upward, apex obtuse, base rounded truncate, sessile, bipinnatifid, pinnule on both sides nearly with same size. Veins obvious abaxially, veinlet forked or pinnate, ending in margin;
lamina herbaceous, yellowish green when dry, sparsely covered with rod-shaped lemon-yellow glandular hairs on both surfaces; rachis and costa sparsely covered with hairs the same to the lamina. Sori rounded, dorsiferous on the upper part of veinlet, one on each lobe; indusium caducous; spore monolete, ellipsoid, perispore irregularly lophate.
Additional specimen examined. CHINA. Guangdong Province, Shaoguan City, Renhua County, Danxia Mountain, Guangdong Province, China, alt. 200 m. 12
Mar 2005, Faguo Wang et al. 1024 (IBSC).
Distribution. Hypodematium humile is restricted to the type locality (Figure 4).
Ecology. It is a rock plant that occurs on rocky tunnels, limestone cliffs, or Danxia (literally, red cloud) mountain. Plants were collected in association with Ctenitopsis devexa (Kunze ex Mett.) Ching & Chu H. Wang, Pteris deltodon Baker, P. ensiformis Burm., Selaginella moellendorffii Hieron. and Lemmaphyllum microphyllum
C. Presl.
Conservation status. It is known only from two sites and its populations are small. Therefore, we consider this species Critically Endangered (CR) according to the IUCN (2001) conservation categories.
Etymology. Named from the Latin word 'humile', a reference to the short individual that distinguishes other species of Hypodematium except H. microlepioides.
Spore morphology. The spore of H. humile is monolete and ellipsoid, and the perispore is irregularly lophate (Figure 2). However, the perispores of related species H. glandulosum and H. crenatum are circinate and striate, respectively.
Morphological notes. Hypodematium humile resembles H. glandulosum Ching ex Shing, which is distributed in Hunan and Guizhou Provinces of China (Shing et al., 1999). Both species have rod-shaped glandular hairs on lamina, rachis, and costa. However, the former differs primarily by having leaf 8-11 cm long; scale 0.4-0.6 cm
Table 2. Diagnostic characters among Hypodematium humile, H. glandulosum and H. crenatum
Characters
H. humile
H. glandulosum
H. crenatum
Leaf length
8-11 cm
12-20 cm
15-55 cm
Petiole
0.5 mm in diameter, sparsely covered with rod-shaped glandular hairs upward
1-1.5 mm in diameter, densely covered with rod-shaped glandular hairs upward
1-3 mm in diameter, pallid pubescent
Lamina
4.5-5.5x5-7 cm, sparsely covered with rod-shaped glandular hairs
7.5-13x8-10 cm, densely covered with rod-shaped glandular hairs
10-30x10-30 cm, densely pallid
pubescent
Rachis and costa
Sparsely covered with rod-shaped glandular hairs
Sparsely covered with rod-shaped glandular hairs
Densely pallid pubescent
Pinna
Sessile except first basiscopic pair
With petiole
With petiole
Pinnulet
Apex obtuse
Apex acute
Apex obtuse
Spore
Perispore irregularly lophate
Perispore circinate
Perispore striate
Indusium
Caducous
Persistent
Persistent
WANG et al. ― Two new species of Hypodematium
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long; petiole c. 0.5 mm in diameter; pinna sessile except first basiscopic pair; surfaces of lamina, rachis, and costa sparsely covered with rod-shaped glandular hairs; apex of pinnule obtuse; indusium caducous; perispore irregularly lophate.
Hypodematium crenatum is widely distributed in subtropical Asia and Africa, and resembles H. humile in having an obtuse pinnulet. However, plants of H. humile have short leaves that are sparsely covered with rod-shaped glandular hairs and perispores that are irregularly lophate. In contrast, plants of H. crenatum have long leaves that are pallid pubescent and perispores that are striate. A morphological comparison between Hypodematium humile, H. glandulosum, and H. crenatum is given in Table
2 (Shing et al., 1999; Zhang et al., 1976).
Hypodematium humile is characteristic by its short leaf and caducous indusium, two features that may well have an adaptive value to dry environment where this species occurs. It was observed that H. humile prefers the southern slopes of the mountain where it grows, this area being dryer than the sites where H. crenatum and H. fordii occur in Guangdong.
Key to the species of Hypodematium from Guangdong
The species of Hypodematium known from Guangdong Province, south China, can be identified with the following key adapted from Wu (2006) and modified to include H. humile, H. villosum, and H. hirsutum.
1. Leaf with rod-shaped glandular hairs.
2. Leaf 35-50 cm tall; indusium persistent ........ H. fordii
2. Leaf 8-11 cm tall; indusium caducous......... H. humile
1. Leaf without rod-shaped glandular hairs.
3. Petiole pallid pubescent ........................... H. crenatum
3. Petiole glabrous except the base.
4. Pinnulet acute, apex without tooth; lamina without
rufous and lanceolate scales abaxially ..................
............................................................. H. villosum
4. Pinnulet oblong, apex with 2-4 teeth; lamina with
rufous and lanceolate scales abaxially ..................
............................................................ H. hirsutum
The relationship of Hypodematium to related taxa
Leucostegia has long been assigned to Davalliaceae because of its creeping, dorsiventral rhizome densely covered by scales, dissected leaves, and indusia (Copeland,
1927; Ching, 1940, 1978; Holttum, 1949; Kato, 1985;
Nooteboom, 1992; Wu, 1999). Molecular phylogenetic analysis has shown that Leucostegia is closely related to Hypodematium (Tsutsumi and Kato, 2006), a genus that has been previously included in Dryopteridaceae but never placed in the Davalliaceae (Smith et al., 2006). Kato and Tsutsumi (2008) discussed the exclusion of Leucostegia from Davalliaceae based on their molecular phylogenetic
results and on morphological and growth form similarities. The spore of Leucostegia immersa is monolete and bean­like, with an irregular and closely verrucate arrangement (Figure 2), which resembles that of Cyrtogonellum caducum (Lu et al., 2007), but differs from Davallia, Humata, Araiostegia and Hypodematium. The results of spore morphology support the exclusion of Leucostegia from Davalliaceae and its placement in Dryopteridaceae. With its dense, persistent and big scales and crowded petioles, Hypodematium is distinct from Leucostegia.
Acknowledgements. The authors sincerely thank Qiu Bo for his help in the fieldwork and Ms. Liu Yunxiao for preparing the illustration. We thank Senior Engineer Hu Xiaoying for her help with spore SEM studies. Dr. Yang Qiner (South China Botanical Garden, CAS), Dr. Javier Francisco-Ortega (Florida International University) and two anonymous reviewers are thanked for their valuable comments. Liang Guanxin is thanked for his help with the spore morphology figure. This work was partly supported by the National Natural Science Foundation of China (30270122, 30800056) and the Knowledge Innovation Program of the Chinese Academy of Sciences (KSCX2-
YW-Z-022).
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中國廣東石灰岩地區腫足蕨屬兩新種
王發國 劉東明 邢福武
中國科學院華南植物園
本文報導中國廣東產腫足蕨屬兩新種：矮腫足蕨 (Hypodematium humile) 和毛葉腫足蕨 (H.
villosum)，提供線繪圖以資辨別，並報導其孢粉形態、生態和保育狀況。毛葉腫足蕨與福氏腫足蕨 (H.
fordii)相似，但葉柄基部以上無毛，葉面兩面連同葉軸和羽軸密被灰白色的細長針狀毛長約1 mm ，裂
片先端急尖，可資區別。矮腫足蕨與腺毛腫足蕨 (H. glandulosum) 近似，不同在於葉長僅8-11 cm ，葉片
兩面連同葉軸和羽軸下麵疏被球杆狀腺毛，囊群蓋早落，可資區別。文中提供中國廣東腫足蕨屬種的檢 索表，並討論了腫足蕨屬與大膜蓋蕨屬的系統關係。
關鍵詞：中國；特有；廣東；矮腫足蕨；毛葉腫足蕨；石灰岩；新種；稀有植物；孢粉形
態。