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The Online Magazine for Sustainable Seas
November, 1998 Vol. 1 No. 11
 


Wanted: The Philippines' Fourth Bakauan

by C.E.Yao



 

 

 

 

   

ecause of their economic value and ability to establish naturally in large areas, bakauans (Rhizophora spp.) are the most popular mangrove species in the Philippines, and probably the world. Their importance is reflected in the way the term "bakauanan" is used in many parts of the Philippines to refer to the mangrove area itself.

There are eight bakauan species under the genus Rhizophora. Five of these – R. mucronata (bakauan babae), R. stylosa (bakauan bato or bangkao), R. apiculata (bakauan lalaki), R .samoensis, R. x lamarckii Montr. (a hybrid between R. apiculata and R. stylosa) and R. x selala – are found in that part of the tropics extending from East Africa to the Western Pacific. These species also occur from Western Africa to the Pacific coast, along with three more species: R. mangle (which is common in Florida, USA), R. x harrisonii (a hybrid between R. mangle and R. racemosa) and R. racemosa.

Three species – R. mucronata, R. stylosa, and R. apiculata – are found in the Philippines. But there could be the fourth bakauan, which I first sighted in Central Visayas at Barangay Okiot, Dewey Island, Bais City in 1984. There, the species was called bakauan hybrid pula to distinguish it from the bakauan babae which has a white terminal bud. It was a solitary tree, occurring in close association with bakauan bato, pagatpat (Sonneratia alba), bakauan lalaki and bakauan babae. It was branchy, 5 meters high with several leaders averaging 10 cm in diameter. It closely resembled the bakauan babae but had a reddish terminal bud similar to that of the bakauan lalaki. It had several flowers but no propagules.

In 1990, I sighted the same species for the second time in Villadolid, Carcar, Cebu, where I was doing a study on nipa tapping. As in Bais City, the tree was solitary, 2 cm in diameter at breast height and 3 meters high, among a strip plantation of bakauan bato protecting a fishpond dike.

I recorded three more sightings of the species. The first occurred in 1990 in Tinguib, Ayongon, Negros Oriental and the last two in 1996 on Panggangan Island in Calape and Handayan Island in Getafe, both in Bohol. The sightings in Bohol confirmed a report by mangrove expert Fred Vande Vusse who believes the species could be R. x lamarckii, a sterile hybrid between bakauan lalaki and bakauan bato (also known as bangkao).

A closer look

Up close, R. x lamarckii belies its genetic make-up, showing little of the visible characteristics of the bakauan bato. Instead it looks more like a cross between the bakauan babae and bakauan lalaki. Its leaves are broad and dark green like those of the bakauan babae, while its flower buds resemble the bakauan lalaki’s, except that they are slightly bigger and their stalks are twice longer, some with more than two buds on a stalk.

I have not seen a specimen whose flowers developed propagules, but the bakauan hybrid is known to produce long propagules, at least according to some reports from Bais City. All my sightings were of solitary trees occurring close to bakauan bato, with some bakauan lalaki nearby. In all cases, I found the style to be about 2 mm long, shorter than that of bakauan bato, broad-based with a pinkish tip and longer than but otherwise similar to the bakauan lalaki's very short and red-tipped style.

I have since gathered additional information on the hybrid, hoping to find more details that would confirm its occurrence in the Philippines. I found a publication by a researcher named Zalvoza ("Key to Genus Rhizophora") dating back to 1936. It describes the species as follows: "Flowers per inflorescence usually 4's (sometimes 2s), peduncle short (about 15 mm long), and rather stout. Stamens variable in number (8-15) 16 (up to 22) and some often distorted, aborted or represented by a filamentous staminate. Petals with inconspicuous marginal hairs. Style 2-3 mm long. Trees usually sterile and not producing seedlings. Pollen sterile... R. x lamarckii Montr. (a possible hybrid R. apiculata x R. stylosa)"

Another report, published by P.B. Tomlinson (Cambridge University Press) in 1986, describes the species as endemic to New Caledonia. "More recently, its existence in isolated localities in Queensland, New Guinea, the Solomon Islands and the New Hebrides has been established on the basis of field observation and herbarium records. On abundant circumstantial evidence, it is recognized as a hybrid of R. apiculata with R. stylosa and always coexist with its putative parents."

In 1996, another author, C. Field, reported that R. x lamarckii "are often sterile and have intermediate structural features of their parental species."

From the above, I am convinced that the species sighted in Central Visayas could be R. x lamarckii. It is likely that this hybrid occurs more widely in the Philippines than has been reported, but because of its close resemblance to the bakauan babae, it is often not distinguished as a separate species. With this article, I hope to stir interest among mangrove experts and enthusiasts in looking for the hybrid. All it takes is a closer look at what appear to be flowering bakauan babae trees: if you see one that bears 2-4 buds on a short stalk with a pink-tipped style, you are likely to have found your R. x lamarckii.



  

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