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Acanthus ilicifolius

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Acanthus ilicifolius, Cairns, QLD.
Photo: M. Fagg, ? ANBG
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Common Names

Spiny Holly Mangrove [1]

Family

Acanthaceae

Name Reference

Acanthus ilicifolius L.

Origin of Name

‘Acantha’ means thorn or thistle (in Greek), and refers to the spiny leaves of some species. ‘Ilici-folius’ means ilex leaves (in Latin), and refers to the holly-like leaves of this species ([1]).

Summary

Acanthus ilicifolius Blanco1.153-cropped.jpg
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Plate from Flora de Filipinas [...] Gran edicion [...] [Atlas I]..., 1880-1883?
Source

Acanthus ilicifolius is typically a low viny herb that grows often in sand on accreting banks, to mud in under canopy patches. It has flowers with pale mauve and white petals. The species often forms large patches where plants scramble over adjacent vegetation for support. Development of adventitious aerial roots compliment and support the sprawling habit. There is considerable variation in leaf form and presence of spines. Spiny leaves are the result of increased sun exposure with spines more numerous on plants growing in exposed frontal stands of accreting estuarine banks, and open canopy back areas ([1]).

Description

Acanthus ilicifolius ( Spiny Holly Mangrove) is a shrub or herb growing 1 - 2 m in height with non-woody stems, smooth bark and often with a pair of spines at the leaf axils. Sometimes aerial or prop roots are present at the base of stems, especially in larger specimens.

The leaves are opposite, simple, oblong to narrowly ovate in shape, shiny green and hairless with a pointed apex. They are 5 - 20 cm long and 2 - 6 cm wide and are often spiny. The presence of spines increases with exposure to sunlight. The petiole is 0.8 - 1.5cm long.

The inflorescence is a spike of purple, pale blue or white flowers. The flowers are zygomorphic with 4 calyx lobes and 4 stamens and are 3.5 - 4 cm long.

The fruit is a smooth, green, egg-shaped or oblong, 2-4 seeded capsule, which is 2 - 3 cm long and up to 1 cm wide ([2],[3], [4], [5]).

Botanical Description

GROWTH FORM

Shrub or herb 1-2 m, non-woody, somewhat viny with sparsely branched stems; bark smooth, green; stem slender, 10 mm W, cylindrical, shiny-green with speckles, often with a pair of spines at leaf axils; roots sometimes aerial or prop roots on lower parts of reclining stems.

FOLIAGE

Leaves opposite, simple, oblong, shiny green, glabrous, to 20 cm L, margins either entire or spiny and dentate, presence of spines with greater sunlight and exposure; petiole short, 1-1.5 cm L.

REPRODUCTIVE PARTS

Inflorescence terminal, forming bracteate spikes 10-20 cm L, spikes extend with age; flowers clustered in 4 ranks, to 20 pairs; flowers perfect, zygomorphic; bract 5 mm shorter than calyx, often caducous; lateral bracteoles 2, conspicuous, persistent; calyx 4-lobed, upper lobe conspicuous, enclosing flower bud, lower lobe smaller, lateral lobes narrow, wholly enclosed by upper and lower sepal; corolla usually mauve to pale blue in colour with white stripes, rarely all white, to 3 cm L, short tube closed by basal hairs; abaxial lip broadly 3-lobed to entire, adaxial lobes absent; stamens 4, subequal with thick hairy connectives; anthers medifixed each with 2 cells aggregated around style; ovary bilocular with 2 superposed ovules in each loculus; style enclosed by stamens, capitate to pointed stigma exposed; fruit 4-seeded capsule, ovoid, green, shiny, smooth, 2-3 cm L, 1 cm W.

DISPERSAL PROPAGULE

Seeds rugose angular, about 1 cm L, germination hypogeal; testa delicate, wrinkled whitish green; cotyledons flattened, green.

([1]).

Distribution

Acanthus ilicifolius is common in estuaries throughout the Asian tropics from India to Polynesia and northern Australia. In Australia, it occurs in estuaries and embayments from the Daly River, Northern Territory (13° 19' S, 130° 14’ E) in the west, to the Fitzroy River, Queensland (23° 31' S, 150° 53’ E) in the east ([1]).

Localities (not complete):

Habitat

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Acanthus ilicifolius, Adelaide River, NT.
Photo: Wrigley, J., ? ANBG
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Acanthus ilicifolius grows as a thicket along tidal waterways and at the landward edge of mangrove zones, predominatly in areas that receive some freshwater flow ([4]). It has also been recorded growing in hypersaline areas ([8]). It generally grows in sand on depositional banks or in mud under patches in the canopy ([3]).

High to low intertidal, intermediate-upstream estuarine position ([1]).

Biology

In Australian, peak flowering occurs from September to December and peak fruiting from January to February, although flowers and fruit can be found all year round ([3], [4]).

Often forms large, scrambling patches, hanging over other plants for support. The spiny leaves are the result of increased exposure to the sun, with plants growing at the exposed edges of stands showing more spines that those growing in the central shadier areas ([3]).

Flowers are adapted for cross-pollination, with the stigma becoming receptive after one day of the flower being open, while the pollen is available the entire time. The pollinator, while probing for nectar at the base of the flower, causes the two pairs of stamens to separate, allowing the stigma to descend and pick up pollen from the pollinators back. The Yellow-breasted Sunbird Nectorinia jugularis has been seen visiting Acanthus spp. in Australia, although large bees (Xylocopa) are likely the main pollinator ([9]). The occasional great abundance of maturing fruits shows that pollination is usually successful ([1]).

Seeds are propelled away with a spinning action like a discus up to 2m distance ([3]).

Commonly associates with Aegiceras corniculatum, Avicennia marina and A. integra ([4]).

Biological Interactions
Group Taxon
  22 taxa
Vascular Plants Acrostichum speciosum
Vascular Plants Aegiceras corniculatum
Vascular Plants Avicennia_integra
Vascular Plants Avicennia marina
Vascular Plants Bruguiera exaristata
Vascular Plants Bruguiera gymnorhiza
Vascular Plants Bruguiera parviflora
Vascular Plants Bruguiera sexangula
Vascular Plants Ceriops pseudodecandra
Vascular Plants Ceriops_tagal
Vascular Plants Cynometra iripa
Vascular Plants Diospyros geminata
Vascular Plants Excoecaria agallocha
Vascular Plants Hibiscus tiliaceus
Vascular Plants Heritiera littoralis
Vascular Plants Lumnitzera littorea
Vascular Plants Lumnitzera racemosa
Vascular Plants Rhizophora mucronata
Vascular Plants Rhizophora stylosa
Vascular Plants Sonneratia caseolaris
Vascular Plants Xylocarpus granatum
Vascular Plants Xylocarpus moluccensis

Ethnobotany

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Distribution of Acanthus ilicifolius in Australia.
Image: Australia's Virtual Herbarium, 2010

A number of Aboriginal languages have names for this plant, although there are no recorded uses. In Malaysia, it is used to treat boils, rheumatism, blood impurities, snake bite and arrow poisoning. It is used as a hair restorer in Papua New Guinea ([5]).

Further ethnobotanical information can be found in ([4]).

Similar Species

Acanthus ilicifolius is distinguished from A. ebracteatus by its flowers being pale mauve, larger (3.5-4 cm L), with persistent large bracteoles (to 1 cm L), and larger fruits (2.5-3 cm L) ([3]).

For illustration of the above distinguishing characters see Mangrove Watch Australia: http://www.mangrovewatch.org.au/index.php?option=com_content&view=category&layout=blog&id=33&Itemid=300171

Differentiation between these two species from foliage alone can be difficult, however, in general, A. ilicifolius has prickly leaves and stems with sharp spines and A. ebracteatus has non-prickly leaves and stems with no spines. A. ilicifolius can posses non-prickly leaves, especially in conditions of low sunlight or strong growth. A. ebracteatus can occasionally possess prickly, toothed foliage, although no NT specimens have been observed with spines in the leaf axis ([4]).

Links

Lovelock, C. (1994). Holly Mangrove ( Acanthus ilicifolius ). Field Guide to the Mangroves of Queensland. Australian Institute of Marine Science. Available online: http://www.aims.gov.au/pages/reflib/fg-mangroves/pages/fgm-2223.html

Peter K. L. Ng and N. Sivasothi (editors) (2001). Jeruju putih Acanthus ilicifolius. Guide to the Mangroves of Singapore. Available online: http://mangrove.nus.edu.sg/guidebooks/text/1046.htm

1792048 Acanthus ilicifolius.jpg
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Acanthus ilicifolius ? CSIRO
-- NormDuke and EmmaClifton - 2011-12-15 - 14:46

References

  1. Duke, N. (2011). Mangroves of Australia. Manuscript. Vers.: 27 Sept 2011. (more)
  2. Lovelock, C. (1993). Field Guide to the Mangroves of Queensland. Australian Institute of Marine Science, Townsville, Qld. Available online: http://www.aims.gov.au/c/document_library/get_file?uuid=c9dcfc2e-6018-4302-8818-5ab3fe01f91f&groupId=30301 (more)
  3. Duke, N.C. (2006). Australia's Mangroves. The authoritative guide to Australia's mangrove plants. University of Queensland, Brisbane. (more)
  4. Wightman, G. (2006). Mangroves of the Northern Territory, Australia: identification and traditional use. Northern Territory. Dept. of Natural Resources, Environment and the Arts, Palmerston. (more)
  5. Wightman, G. (2006b). Mangrove Plant Identikit from north Australia's Top End. Greening Australia NT, Darwin. (more)
  6. Bunt, J.S. (1982b). Mangrove Transect Data from Northern Queensland. Coastal Studies Series, Australian Institute of Marine Science AIMS-CS-82-1. Australian Institute of Marine Science. 41 p. Available online: http://data.aims.gov.au/extpubs/attachmentDownload?docID=2326 (more)
  7. Bunt, J.S. (1997). The Mangrove Floral and Vegetational Diversity of Hinchinbrook Island and the Adjacent Coast. Australian Institute of Marine Science, Townsville. Available online: http://data.aims.gov.au/extpubs/attachmentDownload?docID=3018 (more)
  8. Wells, A.G. (1982). Mangrove vegetation of northern Australia. In. Clough, B.F. (ed.) Mangrove ecosystems in Australia: structure function and management. Australian National University Press, Canberra. (more)
  9. Primack, R.B., Duke, N.C. and Tomlinson, P.B. (1981). Floral morphology in relation to pollination ecology in five Queensland coastal plains plants. Austrobaileya 1(4): 19-62 (more)

All taxa related to Acanthus_ilicifolius

Biological Interactions
Relation Taxon GroupSorted ascending
PollinatedBy Nectorinia_jugularis Birds
PollinatedBy Xylocopa Hymenoptera
HasEpiphyte Bostrychia_calliptera RedAlgae
HasEpiphyte Bostrychia_moritziana RedAlgae
HasEpiphyte Bostrychia_simpliciuscula RedAlgae
HasEpiphyte Catenella_nipae RedAlgae
HasEpiphyte Stictosiphonia_kelanensis RedAlgae
OccursWith Acrostichum_speciosum Vascular_Plants
OccursWith Aegiceras_corniculatum Vascular_Plants
OccursWith Avicennia_integra Vascular_Plants
OccursWith Avicennia_marina Vascular_Plants
OccursWith Bruguiera_exaristata Vascular_Plants
OccursWith Bruguiera_gymnorhiza Vascular_Plants
OccursWith Bruguiera_parviflora Vascular_Plants
OccursWith Bruguiera_sexangula Vascular_Plants
OccursWith Ceriops_pseudodecandra Vascular_Plants
OccursWith Ceriops_tagal Vascular_Plants
OccursWith Cynometra_iripa Vascular_Plants
OccursWith Diospyros_geminata Vascular_Plants
OccursWith Excoecaria_agallocha Vascular_Plants
OccursWith Heritiera_littoralis Vascular_Plants
OccursWith Hibiscus_tiliaceus Vascular_Plants
OccursWith Lumnitzera_littorea Vascular_Plants
OccursWith Lumnitzera_racemosa Vascular_Plants
OccursWith Rhizophora_mucronata Vascular_Plants
OccursWith Rhizophora_stylosa Vascular_Plants
OccursWith Sonneratia_caseolaris Vascular_Plants
OccursWith Xylocarpus_granatum Vascular_Plants
OccursWith Xylocarpus_moluccensis Vascular_Plants