Bull. Natl. Mus. Nat. Sci., Ser. B, 40(3), pp. 107–112, August 22, 2014

Naturalization of Dicksonia antarctica Labill. in Pidurutalagala
Mountain Forest Reserve and Adjacent Eucalyptus Plantationin Sri Lanka
Rajapaksha Haddokara Gedara Ranil1,*, D. K. N. Gamini Pushpakumara1,K. Tilak Premakantha2, Peter D. Bostock3 and Atsushi Ebihara4
1

Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka
2
Sri Lanka Forestry Institute, Nuwara Eliya, Sri Lanka
3
Queensland Herbarium, Department of Science, Information Technology, Innovation and the Arts,Brisbane, Queensland, Australia
4
Department of Botany, National Museum of Nature and Science,
Amakubo 4–1–1, Tsukuba 305–0005, Japan* E-mail: rhgranil@gmail.com(Received 13 June 2014; accepted 25 June 2014)

Abstract Dicksonia antartica Labill. is a species native to Australia. In Sri Lanka, until recently,
the only known record of D. antarctica was at the Fernery in Hakgala Botanic Gardens, Nuwara
Eliya, where the species was planted in 1863. An eco-geographic survey on Sri Lankan tree ferns
conducted from 2006–2013 identiﬁed a substantial population from Pidurutalagala Mountain Forest Reserve and adjacent Eucalyptus plantation. The detailed observation of population in naturalforest and forest plantation fringe revealed natural regeneration with substantial number of immature and mature individuals. Hence, it is proposed that D. antarctica is naturalized in some areas of
Pidurutalagala Mountain Forest Reserve and adjacent Eucalyptus plantation after escaping fromthe Fernery in the Hakgala Botanic Gardens. The substantial amount of population was observed
about 30 km away from the Fernery. Further studies on population and reproductive biology arecontinuing.
Key words : introduction, natural population, population distribution, pteridophytes.

The family Dicksoniaceae is represented bythree genera, namely Calochlaena, Dicksoniaand Lophosoria (Christenhusz et al., 2011). The
genus Dicksonia comprises 20–25 species intropical and temperate areas (Kramer, 1990). The
genus shows a scattered distribution from Malesia through Australia and New Zealand to SouthAmerica. New Guinea is considered as the centreof diversity (Large and Braggins, 2004). Dicksonia antarctica Labill. is native to Australia and isa common and popular species in natural andman-made landscapes (Large and Braggins,2004). Its natural range is across south-eastern
Australia including Tasmania, Victoria, NewSouth Wales and Queensland in moist, shadedand loamy soil habitats. The family Dicksoniaceae is not naturally represented in Sri Lanka.
The only known locality for D. antarctica is at
the Fernery in the Hakgala Botanic Gardens,
Nuwaraeliya where it was established in 1863.
Detailed observations of the Fernery revealed asubstantial number of immature and mature individuals at the Fernery. An eco-geographic surveyof Sri Lankan tree ferns conducted from 2006–
2013 identiﬁed a substantial population of D.
antarctica from Pidurutalagala Mountain Forest
Reserve and adjacent Eucalyptus plantation. Thespecies has not been previously recorded fromnatural habitats. This paper discusses record ofnaturalized population of D. antarctica in Sri

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Rajapaksha H. G. Ranil et al.

Lanka, its taxonomic treatment, ecology and habitat characters, natural regeneration and future
observation to monitor in naturalized populations.
Taxonomic description of naturalized
Dicksonia antarctica
The taxonomic account was made after theinvestigation of immature and mature individualsof both the naturalized population and cultivatedplants at the Hakgala Botanic Gardens. Herbarium specimens have been prepared and depositedat the National Herbarium of the Royal Botanic
Gardens, Peradeniya (PDA).
Dicksonia antarctica Labill., Nov. Holl. Pl.
2: 100, t. 249 (1807) [Fig.1: A–F]
Trunk 1–3.5 m tall, erect, rarely prostrate,unbranched, densely covered with brown ﬁbrousroots, producing offsets. Stipe short, brown, basepersistent, base of stipes and trunk apex densely
covered with glossy ginger-brown hairs. Fronds
large, dense, rosette, spreading crown, 12–30
leaves crowded at the end of the stem. Stipe
20–35 cm long, stout, smooth or slightly verrucose, hairy. Lamina tripinnate, oblong-lanceolate,
2–4.5 m long, 0.5–0.9 m wide, dark green andshiny above, coriaceous. Pinnules divided, linear,sessile, with pointed apex. Veins free and simple.
Sori 0.8–1.3 mm in diameter, numerous, globular,
2–6 per pinnule, marginal, solitary on each lobe.
Indusia circular to oval in outline.
Ecology and habitat characters
Most Dicksonia species occur naturally in theundergrowth of sparse forests, often in thickets
or more open vegetation, and in mountainregions (Kramer, 1990). The preferred natural
habitat of D. antarctica is high-rainfall forestsfrom sea level to about 1,000 m; it is particularly
abundant in wet, shady gullies in south-eastern
Australia (Jones, 1998). Out of its natural habitat,
this species thrives well in cool, moist condition
and, if given plenty of water, will tolerate a fairdegree of exposure to sun (Jones, 1987; Largeand Braggins, 2004). Apparently the cool mountainous micro-climate and high elevation(1,745 m) of the Hakgala Botanic Gardens arematched with the ecological requirements of D.
antarctica. This may be the main eco-physiological reason why D. antarctica was introduced tothe Fernery at the Hakgala Botanic Gardens during colonial era, as a way of popularizing thespecies (Fig. 1A). A similar micro-climatic environment also occurs in the Pidurutalagala Mountain Forest Reserve and adjacent Eucalyptus
plantation. Both the forest area and Eucalyptus
plantation consist of nearly 40–50% canopy
cover and 20–30% steepness. There are two seasonal streams and one perennial stream ﬂowing
in the area. All individuals of D. antarctica areobserved associated with the stream network.
During the study period a total of 30 plants wererecorded. Of which 90% are immature individuals suggesting that it is still in the initial stage ofnaturalization. Though D. antarctica is typically
identiﬁed as a terrestrial species, out of the 27 of
total immature individuals, 18 plants wereobserved on the base of Cyathea walkerae Hook.
and one on another unidentiﬁed tree fern trunk(Fig. 1D). Further observations indicated that asthey grew and developed, these plants formed arhizome and connection with the soil surface.
Naturalization and natural regeneration of
Dicksonia antarctica
Species that have translocated from one region
to another region are deﬁned as alien or exotic to
the newly occupied region (Richardson et al.,2000). Overtime some such exotic species
become naturalized. Such migration is considered as a natural phenomenon which enriches
ecosystems and drives evolution (Hettinger,2001). Though naturalization of pteridophytes
has not been properly studied, this phenomenon
also occurs with the pteridophytes. The theoretical framework of factors mediating naturalization has been well elaborated (Catford et al.,2009; Richardson et al., 2000). To quote Wu etNaturalization of Dicksonia antarctica in Sri Lanka

109Fig. 1. Dicksonia antarctica Labill. A: a well grown mature individual planted in the Hakgala Botanic Gardens.
B: naturalized plant with trailing stem in Eucalyptus plantation adjacent to Pidurutalagala Mountain ForestReserve. C: trunk apex densely covered with glossy ginger-brown hairs. D: juvenile naturalized plant in thebase of tree fern trunk of Cyathea walkerae. E: lower surface of lamina. F: sori in pinnule lobes (×10).

al. (2010) “several hypotheses have been proposed to account for the naturalization preferences of introduced species, including similar
climates (Corlett, 1992)”. Successful introductionof D. antarctica to the Hakgala Botanic Garden
is probably due to climate similarities between
its natural range and the Botanic gardens. Subsequent naturalization in adjacent Pidurutalagala
Mountain Forest Reserve and adjacent Eucalyptus

plantation is also consistent with climate similarity. Fig. 2 shows the relative position of the Fernery of the Hakgala Botanic Gardens and records
where naturalized populations have beenobserved. Based on the topography of the area
and wind directions, it is likely that spores of D.
antarctica have been transported to the Pidurutlagala Mountain Forest Reserve areas. Relative distribution of individuals of Dicksonia antarctica

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Rajapaksha H. G. Ranil et al.

Fig. 2. Relative location of introduced and naturalized populations of Dicksonia antarctica in Sri Lanka (asterisk) and wind directions (arrow). [Source: The National Remote Sensing Agency, India]

under naturalized conditions in Pidurutalagala
Mountain Forest Reserve is shown in Fig. 3.
Intensive observation were also made in othersimilar areas to Pidurutalagala Mountain Forest
Reserve such as Kikiliyamana Forest Reserve,
Hakgala Strict Nature Reserve, Horton Plains
National Park and Bomburu-ella Forest Reserve,
but the species was not observed. However, whyD. antarctica has not been naturalized in othersimilar areas surrounded by the Hakgala Botanic
Gardens remain unclear and deserve further studies.
Botanical exploration of native Sri Lankan
pteridophytes and introduction of exotic species
as ornamental plants began in the British colonialera. Usually pteridophytes are intentionally introduced as ornamental garden plants. Though it ishard to ﬁnd written evidence, many such ornamental pteridophytes have been introduced
through the Botanic Gardens during the Britishcolonial era. Ranil and Pushpakumara (2012)
reported the occurrence of 336 species ofendemic and native ferns and lycophytes in SriLanka. However, the number of introduced andnaturalized species is vaguely deﬁned. After reexamination of checklists of Sri Lankan ferns byAbeywickrama (1978), Sledge (1982) Fernando(2002), Shaffer-Fehr (2006), and Fraser-Jenkins(2008), tentatively proposed about 22 pteridophytes species as naturalized exotics in the country.
There are few well-known examples for thenaturalization of ferns via Botanic gardens in SriLanka. After their introduction as ornamental
plants to the Hakgala Botanic Gardens, threeother well known Australian fern species havebeen naturalized in submontane and montane
ecosystems of Sri Lanka. Doodia media R.Br.
[Blechnum medium (R.Br.) Christenh.] is nativeto Australia and New Guinea (Parris, 1998) andNaturalization of Dicksonia antarctica in Sri Lanka

111

Fig. 3. Relative distribution of individuals of Dicksonia antarctica under naturalized conditions in Pidurutalagala
Mountain Forest Reserve. Note: Canopy diameter is given in cm as a range in left corner of the map.

found in the Hakgala Botanic Gardens as an
introduced garden ornamental plant. Now thespecies is naturalized (Jayasekara, 2006; FraserJenkins, 2008) and fully established in adjacentnatural forests such as the Hakgala Strict NatureReserve, the Bomburu-ella and Kikiliyamana
Forest Reserves and some of the roadside banksin Nuwara Eliya district. Doodia caudata (Cav.)
R.Br. [Blechnum spinulosum Poir.] is also nativeto Australia and now naturalized in the Azores,Madeira, Sri Lanka and South India (Parris,1998; Fraser-Jenkins, 2008). Doodia squarrosa
Colenso [Blechnum zeelandicum Christenh.] isalso native to Australia and New Zealand andnow commonly occurs in adjacent forest to theHakgala Botanic Gardens. Almost all naturalized
species are commonly found in the Central highland of Sri Lanka. Even though D. antarctica
originates in geographically distant areas, it survives well here probably due to ecological similarities.
It is important to report here that D. antarctica
has been identiﬁed as an invasive species in São

Miguel Island, Azores (Arosa et al., 2012). At
present, the distribution of individuals and theirregeneration did not reveal such invasiveness inPidurutalagala Mountain Forest Reserve andadjacent Eucalyptus plantation. However, continuing monitoring of the population is necessary
to identify whether it is, or will become, an invasive alien species in Sri Lanka.
Conclusions
A naturalized population of D. antarctica wasrecorded for the ﬁrst time from Sri Lanka. However, the present observations on D. antarctica
suggest that it is still in the initial stage of theprocess of naturalization. Monitoring and further
evaluation of the species especially with regard
to alien invasive behaviour reported elsewhereare suggested.
Acknowledgments
Mr. G.J.R. Gamage, Field Assistant, Nuwara

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112

Eliya Division, Regional Forest Ofﬁce, ForestDepartment, Nuwara Eliya is acknowledged forhis support during the ﬁeld observations. Department of Forests and Department of Wildlife Conservation are acknowledged for granting permissions to conduct eco-geographic survey of tree
ferns in Sri Lanka. The eco-geographic survey
was funded by the Nagao Natural Environment
Foundation, Japan.
References
Abeywickrama, B. A. 1978. A Checklist of the Pteridophytes of Sri Lanka. National Science Council of SriLanka, Colombo., 18 pp.
Arosa, M. L., Ceia, R. S., Quintanilla, L. G. and Ramos,
J. A. 2012. The tree fern Dicksonia antarctica invades
two habitats of European conservation priority in São
Miguel Island, Azores. Biological Invasions 14: 1317–1323.
Catford, J. A., Jansson, R. and Nilsson, C. 2009. Reducing redundancy in invasion ecology by integrating
hypotheses into a single theoretical framework. Diversity and Distributions 15: 22–40.
Christenhusz, M. J. M., Zhang, X. C. and Schneider, H.
2011. A linear sequence of extant families and generaof lycophytes and ferns. Phytotaxa 19: 7–54.
Corlett, R. T. 1992. The naturalized ﬂora of Hong Kong: acomparison with Singapore. Journal of Biogeography19: 421–430.
Fernando, B. 2002. Ferns of Sri Lanka. 30 pp. The Fern
Society of Sri Lanka. Katuneriya.
Fraser-Jenkins, C. R. 2008. Taxonomic Revision of Three
Hundred Indian Subcontinental Pteridophytes with a
Revised Census-list: A New Picture of Fern-Taxonomy
and Nomenclature in the Indian Subcontinent. 679 pp.
Bishen Singh Mahendra Pal Singh, Dehra Dun.
Hettinger, N. 2001. Exotic species, naturalization and biological nativism. Environmental Values 10: 193–224.
Jayasekara, P. 2006. Blechnaceae. In: Shaffer-Fehr, M.
(ed.). A Revised Handbook to the Flora of Ceylon. Volume XV: Pteridophyta (Ferns and Fern Allies), pp.

40–47. Amrind Publishing Company Private Limited,New Delhi.
Jones, D. L. 1987. Encyclopaedia of Ferns. An Introduction to Ferns, their Structure, Biology, EconomicImportance, Cultivation and Propagation. 433 pp. Timber press, Portland.
Jones, D. L. 1998. Dicksoniaceae. In: Orchard, A. E. andMcCarthy, P. M. (eds.). Flora of Australia, Volume 48:
Ferns, Gymnosperms and Allied Groups, pp. 187–191.
Australian Biological Resources Study/CSIRO Publishing.
Kramer, K. U. 1990. Cyatheaceae. In: Kubitzki, K. (ed.).
The Families and Genera of Vascular Plants, Volume 1.
Pteridophytes and Gymnosperms, pp. 94–99. Springer,
New York.
Large, M. F. and Braggins, J. E. 2004. Tree Ferns. 359 pp.
Timber Press, Portland, Cambridge.
Parris, B. S. 1998. Blechnaceae: Doodia. In: Orchard, A.
E. and McCarthy, P. M. (eds.). Flora of Australia, Volume 48: Ferns, Gymnosperms and Allied Groups, pp.
385–393. Australian Biological Resources Study/CSIRO Publishing.
Ranil, R. H. G. and Pushpakumara, D. K. N. G. 2012.
Taxonomy and conservation status of pteridophyte ﬂoraof Sri Lanka. In: Weerakoon, D. K and Wijesundara, S.
(eds.). The National Red List 2012 of Sri Lanka: Conservation Status of the Fauna and Flora, pp. 148–164.
Ministry of Environment, Colombo.
Richardson, D. M, Pysek, P., Rejmanek, M., Barbour, M.
G., Panetta, F. D. and West, C. J. 2000. Naturalizationand invasion of alien plants: concepts and deﬁnitions.
Diversity and Distributions 6: 93–107.
Shaffer-Fehr, M. 2006 (ed.). A Revised Handbook of theFlora of Ceylon. Volume XV: Pteridophyta (Ferns andFern Allies). 616 pp. Amrind Publishing Company Private Limited, New Delhi.
Sledge, W. A. 1982. An annotated checklist of the Pteridophyte of Ceylon. Botanical Journal of the Linnean
Society 84: 1–28.
Wu, S.-H., Yang, A., Teng, Y.-C., Chang, C.-Y., Yang,K.-C. and Hsieh, C.-F. 2010. Insights of the latest naturalized ﬂora of Taiwan: change in the past eight years.
Taiwania 55: 139–159.