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Rhizophora X lamarckii

Common Names

Hybrid Stilt Mangrove ([1]), Hybrid Stilt-root Mangrove ([2]),Happy Face ([1])

Family

Rhizophoraceae

Name ref

Rhizophora X lamarckii Montrouz.

Origin of Name

Rhizo-phora means 'root bearing' in Greek, referring to the stilt roots characteristic of the genus.

Named in honour of Jean Baptiste Antoine Pierre de Monnet de Lamarck (1744-1829), the French botanist famous for his theory of acquired traits in evolution ([1], [2]).

Synopsis

Rhizophora X lamarckii is a hybrid of R. apliculata and R. stylosa. It is a large tree with conspicuous stilt roots, yellowish-green leaves and flowers with smooth green bracteoles. It is found in mangroves across the top end of the Northern Territory, through to Port Clinton, Queensland.

Botanical Description

Rhizophora X lamarckii is a tree growing to 25 m high. It has light grey, smooth to dark grey, rough, bark, often with the appearance of crocodile skin with angular patches separated by fissures. It has stilt roots extending 2(-6) m above the ground. Aerial roots extend downwards from branches. The stem base is diminished below the stilt roots.

The leaves are simple, opposite, obovate-elliptic to elliptic in shape, bright yellowish-green in colour, waxy above above and dull below, 7 - 15 cm long and 3 - 8 cm wide with a pointed apex and mucronate spike to 6 mm long. The petiole is 1 - 4 cm long. Under surface spots are absent.

The inflorescence is axillary with 2 - 4 (occasionally 1) yellowish-green or cream flowers which are held within leaf clusters. The bracteoles are smooth and green. The flowers have 4 calyx lobes and 4 slightly hairy white petals.

The fruit is rarely found beyond the immature fruit stage. It is a brown-olive coloured inverted pear-shape. The hypocotyl, which rarely develops, is smooth, green and 28 cm long [2], [1], [3] ).

Distribution

The distribution of Rhizophora X lamarckii matches the overlapping distribution of it's parents (R. apliculata and R. stylosa). Found from south east Asia to the western pacific and Northern Australia. In Australia, Rhizophora X lamarckii is found across the northern coastline of the Northern Territory and Cape York, south to Port Clinton, Queensland ([1]).

Localities (not complete):

Habitat

Rhizophora X lamarckii is found as either a large and vigorously spreading tree, emerging from sounding mangroves, or as extensive gnarly thickets in the mid to high intertidal zone, subject to higher salinity and frequent drying ([1]).

In the Northern Territory it is restricted to mangroves with a year-round freshwater input in substrates of sand or mud ([2]).

Biology

In Australia, peak flowering occurs possibly twice during August and September, with propagule maturation during January and March ([1]).

This hybrid rarely produces fertile propagules, but it capable of asexual reproduction by dividing and spreading over large areas ([1]). Fruit has not been found in NT populations ([2]).

Occurs with it's parent species (R. apiculata and R. stylosa) and Bruguiera gymnorhiza as an emergent tree ([1]). Additional associates include Lumnitzera littorea, Ceriops pseudodecandra [as C. decandra] and less commonly Nypa fruticans and Xylocarpus granatum ([2]).

All Rhizophora flowers are thought to be wind pollinated ([7]).

Biological Interactions
Group Taxon
  20 taxa
Vascular Plants Acrostichum speciosum
Vascular Plants Aegialitis annulata
Vascular Plants Aegiceras corniculatum
Vascular Plants Avicennia marina
Vascular Plants Bruguiera gymnorhiza
Vascular Plants Bruguiera parviflora
Vascular Plants Ceriops pseudodecandra
Vascular Plants Ceriops tagal
Vascular Plants Excoecaria agallocha
Vascular Plants Heritiera littoralis
Vascular Plants Lumnitzera littorea
Vascular Plants Lumnitzera racemosa
Vascular Plants Nypa fruticans
Vascular Plants Osbornia octodonta
Vascular Plants Rhizophora apiculata
Vascular Plants Rhizophora mucronata
Vascular Plants Rhizophora stylosa
Vascular Plants Scyphiphora hydrophylacea
Vascular Plants Xylocarpus granatum
Vascular Plants Xylocarpus moluccensis

Ethnobotany

Similar Species

Rhizophora can be distinguished from other genera in the Rhizophoraceae family by the number of calyx lobes (4). Ceriops spp. have 5 calyx lobes while Bruguiera spp. have 8-15. Rhizophora also have large stilt roots compared to the smaller buttresses, knee and prop roots found in Ceriops and Bruguiera and leaves with mucronate tips ([1]).

Rhizophora X lamarckii can be distinguished from other Rhizophora species by it's prolific early flowers, which fill the leafy crowns; smooth green bracteoles; lack of brown spots on the leaf under-surface and slightly hairy linear-lanceolate petals ([1]).

For illustration and further description of the above distinguishing characters see Mangrove Watch Australia: http://www.mangrovewatch.org.au/index.php?option=com_content&view=category&layout=blog&id=39&Itemid=300175

Chan, H.T. (1996). "A note on the discovery of Rhizophora x lamarckii in Peninsular Malaysia".

Journal of Tropical Forest Science 9: 128?130. http://info.frim.gov.my/cfdocs/infocenter_application/jtfsonline/jtfs/v9n1/128-130.pdf.Mangrove Watch: http://www.mangrovewatch.org.au/index.php?option=com_content&view=category&layout=blog&id=39&Itemid=300175

Wikipedia: http://en.wikipedia.org/wiki/Rhizophora_%C3%97_lamarckii

References

  1. Duke, N.C. (2006). Australia's Mangroves. The authoritative guide to Australia's mangrove plants. University of Queensland, Brisbane. (more)
  2. 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)
  3. !McCusker, A. (1984). Rhizophoraceae. Flora of Australia. 22: 1-10. (Australian Government Publishing Service: Canberra.) (more)
  4. 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)
  5. 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)
  6. Boto, K. G. and Wellington, J. T. (1983). Phosphorus and nitrogen nutritional status of a northern Australian mangrove forest. Mar. Ecol. Prog. Ser. 11: 63-69. Available online: http://www.int-res.com/articles/meps/11/m011p063.pdf (more)
  7. Tomlinson, P.B. (1986). The Botany of Mangroves. Cambridge Tropical Biology Series. Cambridge University Press, Cambridge. (more)

Biological Interactions
Relation Taxon GroupSorted ascending
OccursWith Acrostichum_speciosum Vascular_Plants
OccursWith Aegialitis_annulata Vascular_Plants
OccursWith Aegiceras_corniculatum Vascular_Plants
OccursWith Avicennia_marina Vascular_Plants
OccursWith Bruguiera_gymnorhiza Vascular_Plants
OccursWith Bruguiera_parviflora Vascular_Plants
OccursWith Ceriops_pseudodecandra Vascular_Plants
OccursWith Ceriops_tagal Vascular_Plants
OccursWith Excoecaria_agallocha Vascular_Plants
OccursWith Heritiera_littoralis Vascular_Plants
OccursWith Lumnitzera_littorea Vascular_Plants
OccursWith Lumnitzera_racemosa Vascular_Plants
OccursWith Osbornia_octodonta Vascular_Plants
OccursWith Rhizophora_apiculata Vascular_Plants
OccursWith Rhizophora_mucronata Vascular_Plants
OccursWith Rhizophora_stylosa Vascular_Plants
OccursWith Scyphiphora_hydrophylacea Vascular_Plants
OccursWith Xylocarpus_granatum Vascular_Plants
OccursWith Xylocarpus_moluccensis Vascular_Plants
OccursWith Nypa_fruticans Vascular_Plants