Clione+limacina

"One of the most common mangrove tree species"
 * //Rhizophora apiculata// Blume, 1827 **
 * Bakau minyak **

toc Features of //R. apiculata//. Top-left: Flowers on short bracts. Bottom-left 1: Eye-shaped leaves. Bottom-left 2: Stilt roots and aerial roots. Top-right: Grey bark with vertical fissures. Bottom-right: Cylindrical propagule. (Photo: [|Wild Singapore])

= = = = =**Basic Information** =

Name
Binomial: //Rhizophora apiculata// Blume, 1827 Vernacular: Bakau minyak, Bakau putih, Bakau tandok (Tan, 2008), Corky stilt mangrove (Duke, 2006a), Tall stilt-root mangrove (Wightman, 2006), Tall-stilted mangrove (Lovelock, 1993)

First description of //R. apiculata// ([|Blume, 1827]).

**Etymology**

//Rhizo-phora// means 'root bearing' in Greek, referring to the stilt roots characteristic of the genus. //apiculata// means 'to end abruptly' in Latin, referring to the leaf apex (Duke, 2006; Wightman, 2006). 

//R. apiculata// has numerous stilt roots emerging from the stem. (Photo: [|Wild Singapore])

The leaf apex of //R. apiculata// is abrupt and pointed. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka])

**Taxonavigation** Kingdom: Plantae <span style="font-family: Georgia,serif; font-size: 14px;">Phylum: Tracheophyta <span style="font-family: Georgia,serif; font-size: 14px;">Class: Magnoliopsida <span style="font-family: Georgia,serif; font-size: 14px;">Order: Malpighiales <span style="font-family: Georgia,serif; font-size: 14px;">Family: Rhizophoraceae <span style="font-family: Georgia,serif; font-size: 14px;">Genus: Rhizophora <span style="font-family: Georgia,serif; font-size: 14px;">Species: //R. apiculata//

=<span style="font-family: Georgia,serif;">Distribution =

<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// is found in south Asia including Bangladesh, Brunei Darussalam, Cambodia, India, Indonesia, Malaysia, Myanmar, Philippines, Singapore, Sri Lanka, Thailand, southern Viet Nam, and China (Hainan Island). It is also found in the Northern Maldives. In Australasia, its range includes Northwest Australia, Northeast Australia, Federated States of Micronesia, Guam, New Caledonia, Palau, Papua New Guinea, Solomon Islands, and Vanuatu.

<span style="font-family: Georgia,serif; font-size: 14px;">Global distribution of R. apiculata. Adapted from the [|IUCN list of threatened species].

= = =<span style="font-family: Georgia,serif; font-size: 18px;">Description =

<span style="font-family: Georgia,serif; font-size: 16px; line-height: 1.5;">Overall

 * <span style="font-family: Georgia,serif; font-size: 14px;">Trees 20-30m tall
 * <span style="font-family: Georgia,serif; font-size: 14px;">Bark dark grey and chequered
 * <span style="font-family: Georgia,serif; font-size: 14px;">Conspicuous arching stilt roots that can extend 5m up the stem
 * <span style="font-family: Georgia,serif; font-size: 14px;">Often with lots of aerial roots emerging from the branches

<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// along the coast of Thailand. (Photo: [|Britannica Online for Kids])

<span style="font-family: Georgia,serif; font-size: 16px;">Leaves

 * <span style="font-family: Georgia,serif; font-size: 14px;">Leaves 8-15cm long
 * <span style="font-family: Georgia,serif; font-size: 14px;">Eye-shaped
 * <span style="font-family: Georgia,serif; font-size: 14px;">Glossy green
 * <span style="font-family: Georgia,serif; font-size: 14px;">Stiff
 * <span style="font-family: Georgia,serif; font-size: 14px;">Tiny evenly distributed black spots on the underside
 * <span style="font-family: Georgia,serif; font-size: 14px;">Stipule (i.e., outgrowths on the base of leafstalk) usually (but not always) red

<span style="font-family: Georgia,serif; font-size: 14px;">Leaves of //R. apiculata//. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka])

<span style="font-family: Georgia,serif; font-size: 16px;">Flowers
<span style="font-family: Georgia,serif; font-size: 14px;">Flowers of //R. apiculata// grow on very short bracts so that they appear to be stuck directly onto the branch. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka])
 * <span style="font-family: Georgia,serif; font-size: 14px;">Flowers 1-2cm in diameter
 * <span style="font-family: Georgia,serif; font-size: 14px;">In pairs
 * <span style="font-family: Georgia,serif; font-size: 14px;">Grow on short and swollen bracts
 * <span style="font-family: Georgia,serif; font-size: 14px;">Calyx globular, hard, thick, brown on the outside yellow inside
 * <span style="font-family: Georgia,serif; font-size: 14px;">Petals yellow to white, flat membranous and hairless, falling off soon after blossoming

<span style="font-family: Georgia,serif; font-size: 16px;">Fruits
<span style="font-family: Georgia,serif; font-size: 14px;">Pear-like fruits of R. apiculata with long hypocotyls. (Photo: [|Wild Singapore])
 * <span style="font-family: Georgia,serif; font-size: 14px;">About 2cm in length
 * <span style="font-family: Georgia,serif; font-size: 14px;">The fruit looks like a brown, upside down pear
 * <span style="font-family: Georgia,serif; font-size: 14px;">Crowned by short persistent sepals
 * <span style="font-family: Georgia,serif; font-size: 14px;">The cylindrical hypocotyl can be up to 40cm long, smooth, green ripening purple

<span style="font-family: Georgia,serif; font-size: 14px;">Propagules of //R. apiculata// turn purple when ripening. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka])

= = =<span style="font-family: Georgia,serif; font-size: 18px;">Diagnosis =

<span style="font-family: Georgia,serif; font-size: 14px;">//Rhizophora// in Indo-West Pacific region consists of 3 species, //R. apiculata//, //R. mucronata// and //R. stylosa//. They can be distinguished in the field by some easily observed characters. //R. mucronata// and //R. stylosa// have slender (i.e., length much greater than the width) bracts at the base of mature buds and fruits as distinguished from //R. apiculata// that have bracts almost as wide, or wider than the length (Duke, 2006b). In addition, the bark of //R. apiculata// is grey, almost smooth, with vertical fissures, whereas the bark of //R. mucronata// is nearly black or reddish, rough or sometimes scaly (Hanum & Van der Maesen, 1997).

<span style="font-family: Georgia,serif; font-size: 14px;">Left: //R. apiculata//. Middle: //R. mucronata//. Right: //R. stylosa//. //R. mucronata// and //R. stylosa// have slender bracts at the base of fruits, whereas //R. apiculata// have short bracts. (Photo: [|John Yong])

<span style="font-family: Georgia,serif; font-size: 14px;">Left: Grey bark of //R. apiculata//. Right: Black bark of //R. mucronata//. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka 1], [|2])

=<span style="font-family: Georgia,serif; font-size: 18px;">Biology =

<span style="font-family: Georgia,serif; font-size: 16px;">Habitat
<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// is found in the intermediate estuarine zone in the mid-intertidal region. This species tolerates a maximum salinity of 65 ppt and a salinity of optimal growth of 8-15 ppt (Robertson & Alongi, 1992). It grows gregariously on deep, soft and muddy soils that are flooded by normal high tides, often consolidated and sheltered from surf and currents by pioneer species of //Avicennia// L. and //Sonneratia// L.f. It avoids hard soils and develops well in per-humid regions where it can form almost pure stands, sometimes in association with //Bruguiera// spp. or //R. mucronata//. It does not occur in freshwater swamps. It is killed by frost and extended periods of near-freezing temperatures (Hanum & Van der Maesen, 1997).

<span style="font-family: Georgia,serif; font-size: 14px;">//Rhizophora// habits the mid-zone sheltered by pioneer species(Waycott //et al.//, 2011).

<span style="font-family: Georgia,serif; font-size: 16px;">Reproduction
<span style="font-family: Georgia,serif; font-size: 14px;">The tiny flowers are wind-pollinated, producing lots of powdery pollen and no fragrance or nectar. They are also self-pollinating. Insects have occasionally been observed foraging for pollen. One-seeded fruits start to germinate when still hanging on the tree. The root protrudes from the fruit, producing a green, spindle-shaped rod (hypocotyls) of up to 40cm long. Eventually, the seedling falls from the fruit, floats with the high tide and establishes if it reaches a suitable site (Hanum & Van der Maesen, 1997). Seedlings may retain their viability for several months. //Rhizophora// seedlings grow rapidly to avoid being submerged at high tide. They can grow by 60cm in the first year (Tan, 2008).

<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// propagules. (Photos: [|John Yong])

<span style="font-family: Georgia,serif; font-size: 14px;">Development of seedling (Photo: [|A Guide to Mangroves of Singapore])

<span style="font-family: Georgia,serif; font-size: 16px;">Adaptations

 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Prop and Stilt Roots

<span style="font-family: Georgia,serif; font-size: 14px;">In //Rhizophora//, branched, looping roots arise from the trunk and lower branches. At this stage, they are known as prop roots.They become stilt roots only when they take the function of flying buttresses when the tree is older and the bottom of the trunk becomes upside down conical and may even lose contact with the ground. The stilt roots improve the stability of the tree by providing a broader base and support in the soft and unstable mud. They also help in aeration as they are exposed for at least most of the day between tides.

<span style="font-family: Georgia,serif; font-size: 14px;">Prop and stilt roots of R. apiculata. (Photo: [|Checklist of Mangrove species of South East India and Sri Lanka])

<span style="font-family: Georgia,serif; font-size: 14px;">Unlike mangrove species that secrete salt from the leaves, //Rhizophora// uses ultrafiltration at the root level to exclude salt. They can selectively absorb ions from the solutions they come into contact with by ultrafiltration. However, even with this, exclusion is not complete. Some salt is lost by transpiration through the leaf surface or accumulates in some cells of the leaf. It has been suggested that //R. apiculata// might deposit excess salts in the old leaves which are shed.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Ultrafiltration of salt

<span style="font-family: Georgia,serif; font-size: 14px;">Characteristic of //Rhizophora// species, vivipary is the condition whereby the embryo grows first to break through the seed coat then out of the fruit wall while still attached to the parent plant. One suggestion has been that the mangrove presents relatively unstable conditions so having propagules which can grow practically immediately is an advantage. For instance, it is easy to observe that the seedlings of //Rhizophora// can often plant themselves directly below the parent tree because the centre of gravity is close to the root tip.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Vivapary

= = =<span style="font-family: Georgia,serif;">Economical Values =

<span style="font-family: Georgia,serif; font-size: 14px;">The wood is heavy and hard and requires careful seasoning to prevent splitting. It is used for foundations in piling, beams and the outriggers of dugout canoes, as well as furniture and interiors of houses. Branched stilt roots are used for making anchors. It is also a valuable fuelwood species and is often commercially planted for charcoal production. It is sometimes planted to protect bunds and dykes. It is also the preferred species for mangrove silviculture used in mangrove rehabilitation and plantation forestry (Tan, 2008).

media type="youtube" key="TZaeP2WN0PQ" width="420" height="315" <span style="font-family: Georgia,serif; font-size: 14px;">Charcoal making industry in Malaysia. Adapted from [|Youtube].

= = =<span style="font-family: Georgia,serif; font-size: 18px;">Ecological Values =

<span style="font-family: Georgia,serif; font-size: 14px;">Tree climbing crabs and sea snails climb up their aerial roots at high tide to avoid aquatic predators. The roots provide a surface for all kinds of creatures from algae to shellfish. And the tangle of roots provide hiding places for young fishes and shrimps from larger predators. Their branches provide shelter for creatures from Proboscis Monkeys and nesting sites for large herons, to crevices for insects and other tiny creatures.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Refuge

<span style="font-family: Georgia,serif; font-size: 14px;">While on the tree, leaves are eaten by all kinds of creatures. Monkey snack on the shoots and leaves, small insects nibble on them. Fallen leaves are an important source of nutrients both within the mangrove habitat and when it is flushed out to the coral reefs. The leaves are rapidly broken up by crabs and other small creatures, and further broken down by micro-organisms into useful minerals.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Food

<span style="font-family: Georgia,serif; font-size: 14px;">Underwater, a huge number of filter-feeders are fastened on the tangle of roots: barnacles, sponges, shellfish. These filter feeders clean the water of nutrients and silt. As a result, clear water washes out into the sea, allowing the coral reef ecosystem to flourish.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Natural water filter

<span style="font-family: Georgia,serif; font-size: 14px;">Their roots prevents mud and sand from being washed away with the tide and river currents. Mangrove trees also slowly regenerate the soil by penetrating and aerating it (other creatures such as crabs and mud lobsters also help in . As the mud builds up and soil conditions improve, other plants can take root. Mangrove trees also reduce the damage from violent storms.
 * <span style="font-family: Georgia,serif; font-size: 15px; line-height: 1.5;">Coast stabilization

=<span style="font-family: Georgia,serif; font-size: 18px;">Conservation Status =

<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// is widespread and common within its range. It is threatened by the loss of mangrove habitat throughout its range, primarily due to extraction and coastal development, and there has been an estimated 20% decline in mangrove area within this species range since 1980. Mangrove species are more at risk from coastal development and extraction at the extremes of their distribution, and are likely to be contracting in these areas more than in other areas. It is also likely that changes in climate due to global warming will further affect these parts of the range. Although there are overall range declines in many areas, they are not enough to reach any of the threatened category thresholds. This species is listed as Least Concern (Duke //et al.//, 2010).

= = =<span style="font-family: Georgia,serif; font-size: 18px;">Phylogeny =

<span style="font-family: Georgia,serif; font-size: 14px; line-height: 1.5;">The combined Bayesian phylogeny based on chloroplast and ITS data provided strong support to taxon relationships (Lo //et al.//, 2014). //Rhizophora// taxa were divided into three strongly supported clades namely NW, RA, and RMS, corresponding to three groups of taxa. All individuals of //R. apiculata// belong to Clade RA. This clade is further divided into two subclades – one contains individuals from Australia, islands of the NW Pacific (Guam and Micronesia), and subtropical Asia (Japan); and the other contains individuals from Southeast Asia (Malaysia, North Sulawesi, Philippines, and Thailand) and Sri Lanka.

<span style="font-family: Georgia,serif; font-size: 14px;">Genetic relatedness among population samples of Rhizophora. (A) Bayesian tree based on combined chloroplast and nuclear ribosomal ITS data using the GTR + I + G model. Bootstrap (BS; above branch) and posterior probability (PP; below branch) values >50% are indicated. Individuals of Bruguiera gymnorrhiza were used for rooting purposes. (B) Neighbour-joining tree based on Jaccard distances, showing relatedness among population samples of Rhizophora species. Bootstrap values >50% are indicated. (Figure from Lo //<span style="font-family: Georgia,serif; font-size: 14px;">et al. //<span style="font-family: Georgia,serif; font-size: 14px;">, 2014)

<span style="font-family: Georgia,serif; font-size: 14px;">In the Indo-West Pacific, the divergence of //R. apiculata// from //R. mucronata// and //R. stylosa// likely occurred during the Eocene (~38.9 ± 12Ma), although these species co-occur in many areas of the Indo-West Pacific and have a similar wide distribution range. Within Clade RA, the split between {Southeast Asia, Sri Lanka} and the {Australia, Kenya, Northwest Pacific Islands, subtropical Asia} lineages was dated to the Oligocene-Miocene boundary (~29-24 Ma).

<span style="font-family: Georgia,serif; font-size: 14px;">Chronogram of //Rhizophora// based on BEAST analyses of the combined chloroplast and ITS data. White bars indicate confidence interval of the estimated time of divergence of the respective nodes. Pie charts indicate the probable ancestral areas based on Lagrange (black and white) and Mesquite (color) analyses for the clade of interest. (Figure from Lo //<span style="font-family: Georgia,serif; font-size: 14px;">et al. //<span style="font-family: Georgia,serif; font-size: 14px;">, 2014)

=<span style="font-family: Georgia,serif; font-size: 18px; line-height: 1.5;">**Type Information** =

<span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// was first described in Java. Lectotypes can be found in Nationaal Herbarium Nederland, Leiden University branch (L), [|L0009917] and [|L0009918].

= = =<span style="font-family: Georgia,serif; font-size: 18px;">Literature and References = <span style="font-family: Georgia,serif; font-size: 14px;">Blume, C. L. (1827). //Enumeratio plantarum Javae et insularum adjacentium: minus cognitarum vel novarum ex herbariis Reinwardtii, Kohlii, Hasseltii et Blumii.// apud JW van Leeuwen. <span style="font-family: Georgia,serif; font-size: 14px;">Duke, N.C. (2006a). //Australia's Mangroves. The authoritative guide to Australia's mangrove plants.// University of Queensland, Brisbane. <span style="font-family: Georgia,serif; font-size: 14px;">Duke, N. C. (2006b). //Rhizophora apiculata, R. mucronata, R. stylosa, R.× annamalai, R.× lamarckii// (Indo-West Pacific stilt mangrove), ver. 2.1. Species profiles for pacific island agroforestry. //Permanent Agriculture Resources (PAR), Holualoa, Hawaii.// <span style="font-family: Georgia,serif; font-size: 14px;">Duke, N., Kathiresan, K., Salmo III, S.G., Fernando, E.S., Peras, J.R., Sukardjo, S. & Miyagi, T. 2010. //Rhizophora apiculata.// The IUCN Red List of Threatened Species. Version 2014.3. <[|www.iucnredlist.org]>. Downloaded on 24 November 2014. <span style="font-family: Georgia,serif; font-size: 14px;">Hanum, I. F., & Van der Maesen, L. J. G. (1997). //PROSEA: Plant Resources of South-East Asia 11, Auxiliary Plants.// Yayasan Obor Indonesia. <span style="font-family: Georgia,serif; font-size: 14px;">Lo, E. Y., Duke, N. C., & Sun, M. (2014). Phylogeographic pattern of Rhizophora (Rhizophoraceae) reveals the importance of both vicariance and long-distance oceanic dispersal to modern mangrove distribution. //BMC evolutionary biology//, 14(1), 83. <span style="font-family: Georgia,serif; font-size: 14px;">Lovelock, C. (1993). //Field Guide to the Mangroves of Queensland.// Australian Institute of Marine Science. <span style="font-family: Georgia,serif; font-size: 14px;">Robertson, A. I., & Alongi, D. M. (1992). //Tropical mangrove ecosystems// (Vol. 41, pp. 1-330). American Geophysical Union. <span style="font-family: Georgia,serif; font-size: 14px;">Waycott, M., McKenzie, L.J., Mellors, J.E., Ellison, J., Sheaves, M.T., Coller, C., Schwarz, A-M., Webb, A., Johnson, J.E. and Payri, C.E. (2011). //Vulnerability of mangroves, seagrasses and intertidal flats in the tropical Pacific to climate change.// <span style="font-family: Georgia,serif; font-size: 14px;">Wightman, G. (2006). //Mangroves of the Northern Territory, Australia: identification and traditional use.// Northern Territory. Dept. of Natural Resources, Environment and the Arts, Palmerston.

<span style="font-family: Georgia,serif; font-size: 14px;">Useful links: <span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// in [|Wild Singapore] <span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// on the [|NParks Flora and Fauna website]. <span style="font-family: Georgia,serif; font-size: 14px;">//R. apiculata// in [|Guide to the mangroves of Singapore].