128 Journal of Tropical Forest Science. 9(1): 128- 130 (1996)
1 A NOTE ON THE DISCOVERY OF RHIZOPHORA X LAMARCKII IN PENINSULAR MALAYSIA
H.T. Chan
Forest Research Institute Malaysia, Kepong, 52109 Kuala Lumpur, Malaysia
Encountering natural hybrids of mangrove tree species in the field is indeed a rare occasion. Recently, Baba (1994) reported encounterin possiblga hybriw ene Rhizophoraf do apiculata islande th . mucronataf R o Lombof sd o e an on Indonesian n ko i provisionalls ha e H . y named the hybrid R. X lombokensis. As for Malaysia, the occurrence of mangrove hybrids has never been reported before n thiI . s note accounn a , e discover gives th i t n no f Rhizophorayo X lamarckii, naturaa l hybri . apiculataR . sylosa,f R do d Pulan o an u Burun 29.5" , 101g(2 N ' " 50.3' E) in the west coast of Peninsular Malaysia. Located about 100 m off Kampung Sirusa in Port Dickson, Negeri Sembilan, Pulau Burun smala s gi l uninhabited mangrove islan f aboudo hectara t arean epossibli s i t I . o et walk to the island during the low tide as a sand bar has formed linking the island to the mainland. Several coastal habitat type fairlf so y rich species diversit islandfoune e yth ar n do , the main type being the mangrove communities occurring on the littoral mud and sand fiats interspersed with pockets of rocky shore. Species occurring are Avicennia alba, Lumnilzera littorea, Sonneratia alba and R. apiculata. Interestingly, R. stylosa which has been reported to occur only in Pulau Langkawi, Malacca and Johore (Kochummen 1989) is also found here. e morInth e elevated interio islande th f ro , whic seldos hi m inundated, sand ridges have formed and plant species typical of sandy beaches are found. They include Calophyllum inophyllum, Cynometra ramiflora. Guettarda speciosa, Pandanus odoratissimus, Planchonella obovata, Scaevola taccada, Ximenia americana and Termninalia cattapa. The presence of a few individuals f Pterocarpuso indicus, Cocos nuciferad Peltophoruman pterocarpum indicates that the havy yma e been naturalised through water dispersal of seeds from the mainland. n PulaO u Burung e hybrith , easiln dca e mistakeyb . mucronataR r nfo thes a vere yar y similar in terms of leaf shape and size. The main morphological features that distinguish the two are in the number of buds per inflorescence, colour of the buds, length of style and presence/absenc f fruit o ed propagules an s . mucronataR . s inflorescenceha s thae ar t branched 2-3 times bearing 4-8 cream coloured buds. The flower of this species has a stubby style measuring 0.5-1 mm in length and it produces fruits and propagules regularly. On the other hand, the inflorescences of R. X lamarckii bear a single pair of greenish buds although the sometimee yar s branche dfouo t wit p r hu bud s e (FigurflowerTh . 1) es have ae reproductivelnar elongated an m m d 3 ystyl 2- sterile f eo . lamarckiiX . R s generalli y acknowledge a steril s a dl hybri F e. apiculata R f o dd an . stylosa.R s suchA s diagnosti it , c morphological feature consistentle ar s y intermediate to its putative parents (Table 1). Like R. apiculata, R. X lamarckii often produces inflores- cences wit singlha e pai greenisf o r h buds born stoua n eo t bara peduncl s kha wit d han e shallow fissures. Lik . stylosa,R e e hybripala th s eha dgree n midri dard ban k black dott sa the under surface of the leaf which is broadly elliptic and ending in a distinct needle-like tip. Other similar characteristics with R. stylosa include petals which are hairy at the outer edge, stamens with distinct filament styled san s whic elongatede har . Figur demonstratee2 s the variations in the buds between the hybrid, R. apiculata and R. stylosa. Journal of Tropical Forest Science 9(1): 128-130 (1996) 129
Table 1. Diagnostic morphological features of Rhizophora apiculata, R. stylosa and R. X lamarckii
R. apiculata R. stylosa R. X lamarckii
Bark Dark grey with shallow Reddish brown with Brownish with shallow fissures fissureo n s fissures
Leaf Stalk 1.5-, 3cm Stalk 2.5-3.5 cm, Stalk 1.5-2 cm, midrib with pinkish midrib pale green midrib pale green tinge at under surface, at under surface, at under surface, elliptic-oblong to broadly elliptic, broadly elliptic, sublanceolate, apex apex ends with apex ends with blun pointedo t , distinct needle-like distinct needle-like clear venation at tip, faint venation tip, faint venation upper surface, fine uppet a r surface, at upper surface, black dots at under dark black dots at dark black dots at surface under surface under surface
Inflorescence Always with single Branched 2-4 times Often with single pair of buds borne with 4-8 buds borne pair of buds borne on stout peduncle on elongated peducle stoun o t peduncle
Flower Petals glabrous, Petals hairy on Petals hairt ya stamens sessile, the outside, stamens outer edge, stamens style 1 mm with distinct with distinct filaments, style filaments, style 4-5 mm 2-3 mm
Fruit Brown when ripe, Brown when ripe, 2-2.5 cm ovate, 2 cm
Propagule Hypocotyl cylindric, Hypocotyl cylindric, club-shaped with somewhat warty with bluno tt tip p u , pointedo t tipp u , 30cm 30cm
Figure 1. A cluster of inflorescences of the hybrid Rhizophora X lamarckii. Each inflorescence often bears a single pair of greenish buds but occasionally up to two pairs 0 13 Journal of Tropical Forest Science (19960 13 9(1)- )8 12 :
Figure 2. Variations in bud morphological features between the hybrid R. X lamarckii (right) and its putative parents, R. apiculata and R. stylosa (centre and left respectively)
Pulan O u Burung lamarckiiX . ,R coexists wit . apiculatah R . stylosa. R d an Lik putativs eit e parents, tree lamarckiiX s . oR f stuntee ar gnarled dan d with multiple stem extensivd san e looping prop roots. Neither fruits nor propagules were observed on the hybrid individuals durin severae gth lisland e visitth f so . R. X lamarckii was first described from New Caledonia (Tomlinson 1986). It has also been reported to occur in isolated localities of Queensland, Papua New Guinea, the Solomo Hebridesw nNe Islande th .d Wit soccurrencan e hth X. R lamarckii f eo Peninsulan i r Malaysia, its geographical distribution is therefore not confined to the Western Pacific region but may be extended to include Southeast Asia. However, it has yet to be established whethe hybrie rth alss di o foun othen do r mangrove island countre th n si y where bot, hR apiculata and R. stylosa occur together.
Acknowledgements
. Kochummegratefum Ia KM o t l confirminr nfo hybrie gth d base fertiln do e specimens collecte dreviewinr frofo fiele d mth d manuscriptan e gth .
References
BABA, S. 1994. New Hybrid in Rhizophora. Newsletter No. 13 of the International Society for Mangrove Ecosystems (ISSN 0917-3676). KOCHUMMEN,K.M. 1989. Rhizophoraceae. Pp.302-323inNg,F.S.P. (Ed.) Tree Flora of Malaya. Volume 4. Longman Malaysia. TOMLINSON, P.B. 1986. The Botany of Mangroves. Cambridge University Press. 413 pp.