Cyathea nilgirensis Holttum (Cyatheaceae: Pteridophyta):
a threatened tree fern from central Western Ghats, India
Sumesh N. Dudani 1, M.K. Mahesh 2,
M.D. Subash Chandran 3 & T.V. Ramachandra 4
1,3,4 Energy and Wetlands Research Group, Centre
for Ecological Sciences, Indian Institute of Science, Bengaluru, Karnataka
560012, India
1,2 Department of Botany, Yuvaraja’sCollege (Autonomous), University of Mysore, Mysuru,
Karnataka 570005, India
1 sumesh@ces.iisc.ernet.in, 2 mkmahesh44@yahoo.com, 3 mds@ces.iisc.ernet.in, 4 cestvr@ces.iisc.ernet.in
(corresponding author)
doi: http://dx.doi.org/10.11609/JoTT.o3343.3413-5413-6
Editor: C.G. Kushalappa,
College of Forestry, Kodagu,
India. Date
of publication: 26 January 2014 (online & print)
Manuscript details: Ms #
o3343 | Received 13 September 2012 | Final received 21 October 2013 | Finally
accepted 30 October 2013
Citation: Dudani,
S.N., M.K. Mahesh, M.D.S. Chandran & T.V. Ramachandra (2014).Cyathea nilgirensis Holttum (Cyatheaceae: Pteridophyta): a
threatened tree fern from central Western Ghats, India. Journal
of Threatened Taxa 6(1): 5413–5416; http://dx.doi.org/10.11609/JoTT.o3343.5413-6
Copyright: © Dudani et al. 2014. Creative Commons Attribution 3.0 UnportedLicense. JoTT allows unrestricted use of this
article in any medium, reproduction and distribution by providing adequate
credit to the authors and the source of publication.
Funding: The Ministry of Environment
and Forests, Governemnt of India and NRDMS division,
The Ministry of Science and Technology, Government of India for the financial
assistance and infrastructure support.
Competing Interest: The
authors declare no competing interests.
Acknowledgements: We are grateful to the Ministry of
Environment and Forests, Governemnt of India and
NRDMS division, The Ministry of Science and Technology, Government of India for
the financial assistance and infrastructure support. We thank G.R. Rao for the scientific inputs during discussions, Vishnu Mukri and Srikant Naik for their assistance in the field and the Karnataka
Forest Department for providing the necessary permissions.
The Western Ghats of the Indian peninsula
constitute one of the 34 global biodiversity hotspots along with Sri Lanka, on
account of exceptional levels of plant endemism and by serious levels of
habitat loss (Conservation International 2005). It straddles through the states of southern
Gujarat, Maharashtra, Goa, Karnataka, Tamil Nadu and Kerala, practically
forming an unbroken relief dominating the west coast, for almost 1600km from
the mouth of Tapti River to the tip of southern India. The complex physiography of the rugged
mountain chain, the general elevation varying from 400–500 m to
exceptionally high peaks exceeding over 2500m, especially in the Nilgiris and Anamalais, and
rainfall ranging from 1000–6000 mm are major reasons for its rich
biodiversity and high endemism. There are about 2015 endemic flowering plant taxa in peninsular India,
of which about 1600 are confined to the Western Ghats (Chandran et al.
2010). The overall latitudinal and
altitudinal gradients, rainfall patterns brought in by the south-west and
north-east monsoons, reduction in number of rainy months progressively towards
northern latitudes and towards the leeward side of mountains and variations in
soils and rocks coupled with over three millennia of vegetation changes caused
by humans have resulted in a mosaic of ecological islands, niches and refugia favouring with varied degrees of endemism that
reach highest in rare stands of relic forests having conservation histories
since time immemorial.
Several studies have been carried out on
flowering plants of the Western Ghats. However, the lower vascular plants, and in particular pteridophytes have not received much attention. Pteridophytesincluding ferns and fern-allies (lycophytes) are the
earliest of the vascular plants on earth that heralded the arrival of an
advanced vascular system with xylem for water and phloem for food transport
respectively. They grow luxuriantly
in moist tropical and temperate forests from sea level to the high
mountains. The pteridophytesamong the vascular plants with about 12,000 species are next only to the
angiosperms in the world. More than
1,200 species of pteridophytes have been reported
from India (Dixit 1984; Chandra 2000). However, due to the presence of many doubtful species this seems to be
an overestimate hence, the actual number of pteridophytes species are estimated to be
900–1000 (Chandra et al. 2008). The undulating terrain of the Western Ghats supports about 320 species
of pteridophytes (Dudani et
al. 2011).
Prospecting for rare vegetation and their
specific kinds of habitats, based on flowering plant communities, might lead to
the discovery of some rare ferns as well. For instance Cyathea crinita Copel., the Endangered tree fern is found only in
the cooler shola and other high altitude (>1500m) evergreen forests of
southern Western Ghats especially alongside shaded streams (Irudayaraj2011). Similarly, Lycopodium wightianum (Wall.
ex Hook. & Grev.) Holub,a southern Indian species, considered to be Near Threatened (Chandra et al.
2008), has its specific habitats in higher altitudes (1800–2400 m) on
exposed slopes and grasslands (Manickam & Irudayaraj 1992).
While studying some of the exclusive and
threatened swamps overgrown with wild nutmeg trees (Myristicaswamps), in the Kathalekan forest of Uttara Kannada in central Western Ghats (Image 1), several
sensitive fern species were found in association with rare community of
evergreen trees like Myristica magnifica Bedd. (Endangered), Dipterocarpus indicus Bedd.(Endangered), Gymnacranthera canarica (King) Warb.(Vulnerable), Syzygium travancoricum Gamble (Critically Endangered), Semecarpus kathalekanensis Dassapa& Swaminath (newly discovered tree species of
mango family, assessed as Critically Endangered) and scores of other canopy and
understory endemic flowering plants. Mention may be made of southern Indian endemics like Bolbitis subcrenatoides Fras.-Jenk., B. semicordata (Bak.) Ching and others
like the tree fern Cyathea gigantea (Wall. ex Hook.) Holttum,Pteris quadriauritaRetz., Leptochilus axillaris (Cav.) Kaulf,etc. Among the many climax forest relics, Kathalekan(Kathale = dark; kan = sacred forest) relic forest in Uttara Kannada
District, of central Western Ghats in Karnataka is a repository of rare biota
including 35 species of amphibians from an area of 2.25km² (Chandran et
al. 2010).
Cyathea nilgirensis Holttum, a southern Indian endemic tree fern
(Fraser-Jenkins 2008) was seen growing in the deep shade of the swampy forest
of Kathalekan in UttaraKannada. This is a new report of
its distribution anywhere from north of 140latitude in the Western Ghats (Image 2). Tree ferns of the genus Cyathea belong to the family Cyatheaceae which has 241 species
and four hybrids distributed throughout the mountainous regions of the
world (Khare & Srivastava2009). India has 11 species of Cyathea (Dixit, 1984) of which C. nilgirensis was listed ‘Endangered’ (Walter &
Gillett 1998), but subsequently brought into the category of ‘Least Concern’ (Irudayaraj 2011).
Chandra et al. (2008) carried out
extensive work on the distribution and nomenclature of pteridophytesin India and consider that the threat categorization by IUCN of the pteridophytes of India are based on often erroneous names,
taxonomic misunderstandings, and insufficient studies on distribution. This has necessitated a fresh look on
this subject. As Chandra et al.
(2008) is a convincingly good approach towards threat categorization, until a
revision happens in IUCN’s Red Listing of Indian pteridophytesand as a lone population of few individuals of C. nilgirensissurvives precariously in the threatened swamps of Kathalekanin Uttara Kannada, the northernmost range of its
distribution in the Western Ghats, we felt it reasonable to endorse its Near
Threatened status.
The fern is also, notably, listed in the
Appendix-II of CITES (Convention of International Trade in Endangered Species
of Wild Fauna and Flora) (Sanjappa & Lakshminarasimhan 2011). It is distributed in restricted pockets
in the shady and damp streamside forests of Kerala, Karnataka, Tamil Nadu and
Andhra Pradesh. It was reported
from Kemmangundi and CharmadiGhats of Chikmagalur District, Mercara-Bhagamandala-Talacauveri stretch in KodaguDistrict and in Sakleshpur and Devalkerein Hassan District (Rajagopal & Bhat 1998) and now from south of UttaraKannada, central Western Ghats. In Kathalekan, the species exists precariously, with merely
four individuals left, obviously the last relics of what would have been once a
primeval forest before the introduction of agriculture and forestry operations
by humans.
Cyathea nilgirensis Holttum
in Kew Bull. 19: 468. 1956; Nayar & Kaur, Comp. (syn.: Alsophila nilgirensis (Holttum) R.
Tyron) is noted for unbranched trunk of 2–4 m
height, 12–13 cm in diameter; bearing crown of fronds at the apex and
scales densely covering the younger fronds. Stipes swollen at base, bearing small hairs. Lamina bipinnate,
oblong-lanceolate, pinnae about 12 pairs, alternate,
distinct petiolate, pale green below, dark green
above, texture herbaceous. Pinnules acuminate, margin pinnatifidup to the costa; ultimate lobes about 15 pairs, alternate, oblong, 1.5x0.4 cm,
margin crenate. Sorisituated on the vein forks of the lower half of the segments, exindusiate, paraphyes intermingled with sporangia, spores trilete. Grows
as terrestrial species along shaded stream banks (Manickam& Irudayaraj 1992). This can be easily differentiated from
the other commonly occurring species C. giganteawhich has a characteristic “V” shaped soralarrangement in each pinnule lobe and margin of pinnae
lobed 2–5 mm towards the costa.
C. nilgirensis prefers habitat with relatively higher moisture
content such as Myristica swamp. With their little known biota, the Myristica swamps are virtually live museums of
ancient life of great interest to biologists. Such swamps of high watershed value and
evolutionary significance (the Myristicas are
considered among the most primitive flowering plants) have been practically on
the road to extinction due to neglect and need for industrial softwoods and
agricultural expansion. These
swamps were reported for the first time from the Travancore region (Krishnamoorthy 1960) and classified under a category called
‘Myristica Swamp Forests’ under the sub-group 4C by
Champion & Seth (1968). The dipterocarp forests of Kathalekan,
laced with Myristica swamps were
considered significant areas for conservation because of their primeval
characters (Chandran & Mesta 2001; Chandran et al. 2010). Over the last few centuries, most of theMyristica swamps that normally occur along
sluggish streams in primeval forests favored habitats
of ferns like C. nilgirensis, have
unfortunately given way to secondary forests, savannas,
monoculture tree plantations, cash crops such as tea, coffee, arecanut and rubber, rice fields etc. (Chandran & Mesta
2001; Gururaja et al. 2007).
The swamps of Kathalekanare seriously threatened habitats because of stream diversions to adjoining
cultivation areas, depriving many downstream species including the sensitive
fern community of the much needed water for summer
survival. Trampling of ground
vegetation by domestic cattle from adjoining villages has suppressed the
regeneration of the tree ferns. Moreover, the proposed widening of Honavara-Bengaluru
National Highway passing adjacent to Kathalekan could
as well be disastrous to tree ferns including C. nilgirensis,
some of the last relics of the Mesozoic tree ferns.
The Biodiversity Act (2002), of the
Government of India has provisions enough to declare such important
biodiversity areas like Myristica swamps with
their endemism rich biological community as ‘Biodiversity Heritage Sites’. However, the initiatives are yet to be
taken by the State Biodiversity Board and the Forest Department of
Karnataka. The Department however
has taken some steps to remove encroachments from swamps while also creating
awareness on these threatened habitats and making efforts to restore swamp
habitats through involvement of scientists and local village communities. Such actions, if coupled with
introduction of the seedlings of these ferns in suitable habitats and botanical
gardens and attempts to conserve the germplasm of it
through mapping and conservation of all its habitats and application of tissue
culture techniques for its rapid multiplication can be definitely helpful for
the future of this fern.
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