Researchers Finds Mangrove Species in Ryuku Islands in Japan Are Isolated Implicating Conservation

Researchers have discovered that the mangrove populations in the Ryukyu Islands are highly separated from one another, which has consequences for conservation, by applying methods from both genetics and oceanography.

Rhizophora stylosa

(Photo : Maxwell Ridgeway/Unsplash)

This mangrove tree is still regarded as being rare, and can be found on some coasts of Singapore like Chek Jawa and Pulau Semakau having significant populations of them, in the heart of the Sentosa Serapong golf course, a lagoon with large numbers of them may be seen, as per Wild Fact Sheets.

The tree is up to 10 meters tall with one or more trunks.

Often developing vast loops far from the stem, stilt roots can reach lengths of up to 3 meters, with fissured and gray to black bark.

Flowers are one to two cm or more on long, branched stalks that hang down from the branch, with white, thick, and egg-shaped bracts.

It has abundant, woolly hairs along the margins, and the petals are slender and delicate.

After blooming, the petals quickly fall off. Style is 0.4 to 0.6 cm. The pollination of the flowers is thought to occur by the wind.

It is occasionally confused with Bakau kurap (Rhizophora mucronata), which has longer, pimple-covered propagules and bigger leaves.

It is used to make charcoal, fuel, and lumber.

The Australian aborigines utilize it to craft ceremonial items like boomerangs and spears. Light wine and a remedy for blood in the urine are both made from the fruit.

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Journey of a Mangrove Tree in Japan

P.h.D candidate Maki Thomas, the first author of this work that was presented in Frontiers in Marine Science, stated that the goals of conservation drive her research, as per ScienceDaily.

Although it would be wonderful if researchers could preserve every mangrove forest, this is not feasible.

With that, finding regions that need to be protected first is the aim. For instance, fully secluded woodlands that, if destroyed, won't naturally regrow.

Depending on the species, the propagules that the trees drop into the water will float for a few days to a few months before sinking once they have found an ideal environment for germination.

Rhizophora stylosa, the species that was used in this investigation, develops propagules that can endure at sea for several months.

The study employed two distinct approaches to address their question about population connection, one based on genetics and the other on oceanography.

The main island of Okinawa, Miyako, Ishigaki, and Iriomote is the four Ryukyus islands where the scientists' initial sampling of mangroves was conducted.

Thomas was interested in testing the distance propagules from Iriomote and the main island of Okinawa would travel. To determine how closely connected the various populations were, she employed microsatellite DNA, which was tiny DNA pieces extracted from each mangrove sample.

It would indicate that propagules from Iriomote are moving to Okinawa on the currents if, for instance, a mangrove from Iriomote and a mangrove from that island shared a striking genetic resemblance.

On the other hand, significant genetic structural variations can indicate that populations are separate from one another.

The Ryukyu Islands' mangrove populations were determined to have very little connection using both approaches.

Genetic and oceanographic investigations show that Okinawa's main island attracts very few mangrove propagules from other places, according to the data.

Mangroves on other islands did, however, exhibit some of the genetic characteristics of the main island of Okinawa.

In general, the archipelago experiences infrequent, sporadic genetic exchange. A third of the GPS buoys beached on Iriomote, but most were carried into the Pacific by the Kuroshio current.