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Bruguiera X rhynchopetala

Common Names

Hybrid Orange Mangrove ([1])

Family

Rhizophoraceae

Name ref

Bruguiera X rhynchopetala (W.C.Ko) X.J.Ge & N.C.Duke

Origin of Name

Bruguiera is named after the French biologist and explorer Jean-Guillaume Bruguiere (1750-1798), who was famous for his naming of molluscs, marine life and plants.

‘rhyncho-petala’ means beaked petals (in Greek), and refers to the bristles at the tips of petal lobes of this hybrid species [2].

Summary

Bruguiera X rhynchopetala is a hybrid of Bruguiera gymnorhiza and B. sexangula. It is usually a columnar tree growing to 15 m in height and is similar in appearance to B. gymnorhiza. In Australia, this hybrid occurs on the north-east coast of Queensland where populations of the parent species overlap.

Species Feature - Open flower showing petals with 1-2 shortish hairs at lobe tips [2].

Description

Bruguiera X rhynchopetala is a columnar or multi-stemmed tree or shrub growing to 15 m high. It has grey bark with longitudinal and checkered fissuring. There are fin-like buttresses at the base of the trunk, with occasional low-placed prop and aerial roots, and knee-like air-breathing roots (pneumatophores).

The leaves are simple, opposite, glossy green, smooth, elliptic-oblong in shape, 11 - 21 cm long, 4 - 8 cm wide, with a pointed apex. The leaves occur in clusters at the end of branches and the petiole is green and up to 5 cm long.

The inflorescence is one-flowered and axillary. Flowers have a calyx that is green with a rosy blush, 10 - 12 calyx lobes, 20 - 24 stamens and 10 - 12 creamy-orange, bi-lobed petals with 2 - 3 bristles on each apex and 1 conspicuous bristle in the sinus (indentation between the petal lobes) that is shorter than the petal lobes. The viviparous propagule grows from within the calyx and is cigar-shaped and green, with slight longitudinal ribbing and is up to 11 cm long and 1 - 2 cm wide ([1]).

Botanical Description

GROWTH FORM

Tree or shrub to 15 m, evergreen, columnar or multi-stemmed; bark grey, fine longitudinal and checkered fissuring; stem with fin-like buttresses, occasional prop aerial roots low-placed; roots knee-like pneumatophores.

FOLIAGE

Leaves opposite, simple, elliptic-oblong, glossy green, smooth, 11-21 cm L, 4-8 cm W, margin entire, apex pointed, base cuneate; petiole green, to 5 cm L; stipules paired, lanceolate, enclosing terminal bud, to 8 cm L, occasional pinkish tinge.

REPRODUCTIVE PARTS

Inflorescence axillary, 1-flowered, peduncle to 1 cm L, green; flowers green with rosy blush to all green, recurved, to 3.4 cm L; calyx tube turbinate, ribbed, with 10-12 narrow pointed lobes longer than tube, 1.8-2.1 cm L; petals 10-12, creamy orange, 14-17 mm L, bilobed, 5-6 mm L, apices blunt with 2-3 bristles 1-2 mm L, sinus between with spine not exceeding lobes; stamens 20-24, 2 enclosed in each petal, dehiscing precociously; style slender, minutely 3-4-lobed stigma; fruit within calyx tube, enlarged, turbinate, ribbed, grooved, lobes slightly reflexed; germination viviparous, hypocotyl emergent from calyx during maturation.

DISPERSAL PROPAGULE

Hypocotyl cigar-shaped, terete, elongate, green, slight longitudinal ribbing, to 11 cm L, 1-2 cm W, distal tip blunt, buoyant.

[2].

Distribution

Bruguiera X rhynchopetala is a hybrid form with a distribution expected to match the overlapping distribution of the two putative parents, B. gymnorhiza and B. sexangula. It is recorded from Hainan Island in China and from northern Australia. In Australia, the hybrid is found in east coast estuaries of Queensland from Jacky Jacky Creek (10° 54' S, 142° 32’ E) in the north, to the Herbert River (18° 32' S, 146° 19’ E) in the south east ([1]).

A single specimen of Bruguiera X rhynchopetala was recorded from north-east Arnhem Land, but died in the early 1990s. Wightman (2006) suggests it likely that other individuals of this hybrid occur in the Northern Territory where populations of B. gymnorhiza and B. sexangula overlap ([3]).

Localities (not complete):

Habitat

Mid intertidal, intermediate-upstream estuarine position [2].

Biology

In Australia, flowering has been observed during August to September, and propagule maturation during January and February.

While maturing hypocotyls have been observed, recent genetic studies confirm the hybrid status for populations in China (Yanfeng, Qiongshan on Hainan Island) and Australia (Daintree River in Queensland) [2].

Ethnobotany

No ethnobotanical information available.

Similar Species

Bruguiera can be distinguished from other genera in the Rhizophoraceae family by the number of calyx lobes (8-15). Ceriops spp. have 5 calyx lobes while Rhizophora spp. have 4.

Bruguiera X rhynchopetala is similar in appearance to B. gymnorhiza. It can be can be distinguished by it's growth form, an emergent tree with a columnar trunk like a telegraph pole, and short buttresses like rocket fins. Bruguiera X rhynchopetala can be distinguished from B. parviflora, B. cylindrica by it's large, soliatry-flowered inflorescence and petal spine shorter than the petal lobes. It can be distinguished from B. gymnorhiza and B. sexangula by it's rounded petal lobes with 1 - 2 short bristles ([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=35&Itemid=300173

-- NormDuke and EmmaClifton - 2012-06-14 - 12:13

References

  1. Duke, N.C. (2006). Australia's Mangroves. The authoritative guide to Australia's mangrove plants. University of Queensland, Brisbane. (more)
  2. Duke, N. (2011). Mangroves of Australia. Manuscript. Vers.: 27 Sept 2011. (more)
  3. 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)
  4. Duke, N.C. and Ge, X.-J. (2011). Bruguiera (Rhizophoraceae) in the Indo-West Pacific: a morphometric assessment of hybridization within single-flowered taxa. Blumea 56: 36-48. (more)