ANCISTROCLADUS BENOMENSIS ( ANCISTROCLADACEAE ) : A NEW SPECIES FROM PENINSULAR MALAYSIA

The monotypic genus Ancistrocladus Wall. (Ancistrocladaceae) comprises approxi­ mately 20 species (Gereau, 1997) and is characterized by a disjunct distribution in the palaeotropics with two areas of speciation, one in tropical West and Central Africa and one in South East Asia. All taxa are scandent shrubs or woody lianas with tendril­ like modified shoots provided with characteristic circinate woody hooks as climbing devices. Recently a synoptic revision of the African taxa of the genus Ancistrocladus has been presented by Cheek (2000), with an identification key and detailed information concerning taxonomy, distribution, and ecology of the 13 species recognized. For the Asian taxa an equivalent comprehensive study is still lacking and there is much uncertainty in the delimitation of taxa as well as on ecological preferences, seed set, pollination, and flowering rhythm. Concerning taxonomy one has to refer to a synopsis presented by Gilg (1925) and to an annotated checklist of species which was compiled by Gereau (1997) based on a survey of local floras. In this latter overview a detailed account on the typification for 25 binominals is presented, including 12 valid species recognized by the author for South East Asia: A. attenuatus Dyer, A. carallioides Craib, A. cochinchinensis Gagnep., A. extensus Wall. ex Planch., A. griffithii Planch., A. hainanensis Hayata, A. hamatus


INTRODUCTION
The monotypic genus Ancistrocladus Wall.(Ancistrocladaceae) comprises approxi mately 20 species (Gereau, 1997) and is characterized by a disjunct distribution in the palaeotropics with two areas of speciation, one in tropical West and Central Africa and one in South East Asia.All taxa are scandent shrubs or woody lianas with tendril like modified shoots provided with characteristic circinate woody hooks as climbing devices.
Recently a synoptic revision of the African taxa of the genus Ancistrocladus has been presented by Cheek (2000), with an identification key and detailed information concerning taxonomy, distribution, and ecology of the 13 species recognized.For the Asian taxa an equivalent comprehensive study is still lacking and there is much uncertainty in the delimitation of taxa as well as on ecological preferences, seed set, pollination, and flowering rhythm.
Concerning taxonomy one has to refer to a synopsis presented by Gilg (1925) and to an annotated checklist of species which was compiled by Gereau (1997) based on a survey of local floras.In this latter overview a detailed account on the typification for 25 binominals is presented, including 12 valid species recognized by the author for South East Asia: A. attenuatus Dyer, A. carallioides Craib, A. cochinchinensis Gagnep., A. extensus Wall. ex Planch., A. griffithii Planch., A. hainanensis Hayata, A. hamatus (Vahl) Gilg, A. harmandii Gagnep., A. heyneanus Wall. ex J. Graham, A. tectorius (Lour.) Merr., A. wallichii Planch., and A. thwaitesii Tiegh. (according to Harriman (1987) probably a synonym of A. hamatus), neglecting A. stelligerus Wall.ex A.DC. and considering A. vahlii Arn. as a synonym of A. hamatus.Contrary to this taxonomic concept, Van Steenis (1948) had previously lumped all species from South East Asia under A. tectorius (Lour.)Merr.because of difficulties distinguishing vegetative mate rial.
Indeed, the Ancistrocladus tectorius complex exhibits a wide range of variation in morphological features and its elements have never been comprehensively examined with respect to their taxonomic delimitations.Especially the lack of floral and fruit characters which are of significant diagnostic value, complicates the delimitation of species.This is due to the fact that many Ancistrocladus taxa climb in rather tall trees and have small inconspicuous flowers that wither very rapidly.There is also the fact that most species treated are known only from a few localities, which is reflected in nearly all revisions (Cheek, 2000) and floristic treatments (Van Steenis, 1948).The situation is indeed even more complicated because all Asian species have been collected and described before 1925, often in vegetative state only, the type specimen of A. tectorius even dates back to 1790 (basionym Bembix tectoria Lour.) and consists only of poor fragments (Moore & Tandy, 1927).
Originally doubts about the 'onespecies concept' of Van Steenis (1948) arose from comparing phytochemical studies of 'A.tectorius' material collected from geographi cally disjunct areas, e.g., in Hainan (Chen et al., 1981;Bringmann & Kinzinger, 1992;Tang et al., 2000), Laos (Foucher et al., 1975), Central Thailand (Ruangrungsi et al., 1985), Southern Thailand (Manfredi et al., 1996), and Southern Peninsular Malaysia (Montagnac et al., 1995).The strong geographical correlation of the observed structures and the yet different naphthylisoquinoline alkaloid spectrum of A. cochinchinensis from the type location in Vietnam (Nguyen et al., 1997) hint at the occurrence of several separate species.In addition, the examination of Ancistrocladus using molecular mark ers indicates that the A. tectorius complex could be split into at least 9 species in South East Asia.Detailed results will be published elsewhere (Meimberg et al., submitted).
A rich collection of Ancistrocladus plants from different sites in South East Asia is meanwhile in cultivation at the Botanical Garden of Würzburg to study seedling and flower development including phytochemical composition and biosynthesis under controlled conditions.This collection is the basis for the description of further species indicated by molecular methods.The availability of flowers from A. benomensis in the greenhouse (export permit no.WKL00/149) is a first success in our effort to gain basic biological data for the Ancistrocladus complex in South East Asia.

MOLECULAR DATA
In a phylogenetic analysis using sequences of the internal transcribed spacers (ITS1 and ITS2, nuclear rDNA) and the trnK intron (chloroplast DNA), A. benomensis differs in both markers from Ancistrocladus samples from all over South East Asia (75 samples from 24 locations were investigated, details will be published elsewhere).The ITS se quence of A. benomensis was equal in all four samples investigated and shows at least eight different positions to the other samples, while the most closely related sequence is from a sample from South East Thailand, c. 850 km away.This relationship was also indicated using similarity analysis of Inter Simple Sequence Repeat PCR (ISSR).The trnK intron sequence shows at least four different positions to the other samples, while the most similar sequence is from a sample from Southern Malaysia.

CHEMOTAXONOMIC DEMARCATION
Phytochemical investigations (Bringmann et al., 2004) of bark and leaf material of A. benomensis with respect to its characteristic natural products, the naphthylisoquino line alkaloids (Bringmann & Pokorny, 1995), revealed that the plant is unequivocally different from all the other known Ancistrocladus species, in particular from the only known Malaysian one, A. tectorius (Montagnac et al., 1995).Thus, it possesses the highest number of fully dehydrogenated naphthylisoquinoline alkaloids ever isolated from any other known Ancistrocladus species, among them the first optically active fully aromatized naturally occurring Dioncophyllaceaetype (Bringmann & Pokorny, 1995) alkaloids (i.e., without an oxygen function at C6).Another unique feature of the new species is the isolation of the first fully aromatized naphthylisoquinoline alkaloids with a hydroxymethylene group at C3 (Bringmann et al., in press).

DESCRIPTION
Based on evidence from different sources we provide a description of an phytochemi cally unusual Ancistrocladus species discovered in 1999 from an isolated mountain of Peninsular Malaysia based on complete material including all stages of flowering and fruits, which is morphologically, phytochemically, and genetically distinguishable from all other South East Asian species.
Ecology -The species occurs from 500 to 1180 m above sea level on the slopes of Gunung Benom situated in the Kerau Game Reserve, which forms one of the last contiguous Dipterocarpaceae lowland forests in South East Asia.
Etymology -The species name refers to the type locality.'Benom' is an old Mon Khmer word for 'mountain'.
Note -Ancistrocladus benomensis is very similar to A. tectorius, which was de scribed from Vietnam by De Loureiro (1780) as Bembix tectoria.Based on his short description and the notes on Loureiro's specimen by Moore & Tandy (1927), the spe cies from Peninsular Malaysia differs from A. tectorius in having alternate, sessile, obovatelanceolate leaves, bright red flowers, 5 sepals, and a dichotomously branched inflorescence with 50-70 flowers.Ancistrocladus tectorius has opposite, cuneiform leaves with a short and broad petiole, pale flowers, 3 sepals, and a weakly branched inflorescence with only a few flowers.

Fig. 2 .
Fig. 2. Ancistrocladus benomensis Rischer & G. Bringmann.a. Flower in bud; b. young flower with contorted petals; c. flower with view on reflexed sepals and petals; d. flower with 5 spots on inner surface of petals; e. flower longitudinally cut, part of perianth and stamens removed; f. sepals with glands; g. petal, inner surface with adnate stamens; h.ovary with three short styles; i. mature nutlike fruit with enlarged calyxwings (a-g: holo; h, i: from locus classicus; all: Heubl, M).