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Home , Aceratium, Antidesma, Calospatha, Ceratolobus, Christensenia (plant), Crinodendron

Malesian distributions 243 Patterns of distribution of Malesian vascular

W J Baker1, M J E Coode, J Dransfield, S Dransfield, M M Harley, P Hoffmann and R J Johns The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AE, UK 1Department of , Plant Science Laboratories, University of Reading, Whiteknights, Reading, Berkshire, RG6 6AS, UK

Key words: biogeography, phytogeography, palynology, SE , Malesia, Palmae, Gramineae, Euphorbiaceae, , Antidesma, Elaeocarpus, Nypa, Spinizonocolpites

Abstract analytical phase Biogeographical work con- cerned with the analytical phase has appeared A miscellaneous selection of Malesian plant distributions is increasingly in the systematic literature and it is presented, including examples from the Palmae, here that modern methods are most evident Gramineae, Euphorbiaceae, Elaeocarpaceae, and various genera Hypotheses of the tectonic evolution of the Previously, most classifications have been based area may be required to explain many of the observed pat- on intuition and overall similarity which, though terns that are described Two major distribution types are they may stand the test of time, are nevertheless identified repeatedly, the first displaying a strongly Sundaic subjective Despite the introduction of statistical bias and the second focusing on E Malesia Patterns involv- techniques which aimed to make similarity- ing are complex as they tend to include a vari- able combination of other islands such as , , based or phenetic classifications more testable, the Bismarck archipelago and the islands of the W Pacific A theoretical objections have led to the decline of number of striking disjunctions exist, some of which have phenetics in favour of cladistic methods relatively narrow overall ranges, such as those of the palm Cladistics uses character patterns of extant or- genera Cyrtostachys and Rhopaloblaste which occur across ganisms to construct a hypothesis of their evolu- Malesia excluding central parts of the region In other exam- tionary or phylogenetic relationships These pat- ples, however, the separation is more profound including disjunctions between parts of Malesia and Madagascar in terns are generally visualised in the form of Orania (Palmae) and (Gramineae), and between branching diagrams or cladograms which can be , Vanuatu and Palawan in Veitchia (Palmae) At this interpreted appropriately stage, the significance of these distributions for the under- This paper is concerned mainly with the nec- standing of the geological history of SE Asia remains un- essary precursors to the analytical phase, the clear It is noted that distributions of from the Antidesma (Euphorbiaceae) are more easily explained in descriptive and narrative phases of biogeogra- terms of dispersal and environmental factors Formal phy In selecting taxa for discussion we have cladistic biogeographic analyses of these and other groups chosen only those which we believe will prove should aid interpretation of the region’s history to be sound when subjected to the rigours of cladistics The only groups which are acceptable in the cladist’s eyes are those described as Introduction monophyletic A monophyletic (natural) group contains all the descendants of a common an- Over the last four decades, there has been a cestor and is defined by shared characters, or radical change in the methods used by systema- synapomorphies, that support a specific node tists to classify organisms This change has had a on a cladogram A group which contains some, concurrent effect on biogeographical methods but not all descendants of a common ancestor Ball (1975) describes three phases in biogeo- may appear to be coherent, but cannot be de- graphical studies which he calls the descriptive fined in the same way and, indeed, it can be or empirical phase, the narrative phase and the argued that it cannot be defined at all These

Biogeography and Geological Evolution of SE Asia, pp! 243-258 Edited by Robert Hall and Jeremy D! Holloway © 1998 Backhuys Publishers, Leiden, The Netherlands 244 W- J- Baker et al- paraphyletic groups are a partial and arbitrary represented in the region except for the expression of the product of common ancestry Phytelephantoideae and make no sense in an evolutionary context Palm distributions in the region have been The inclusion of non-monophyletic groups in discussed previously in an anecdotal fashion biogeographical studies is flawed for these rea- (Dransfield, 1981, 1987; Uhl and Dransfield, sons For basic introductions to cladistic theory, 1987) but these discussions lack a firm cladistic general overviews may be found in Patterson basis However, with the explicit analytical (1982), Wiley et al- (1991) and Scotland (1992) framework that we are developing, we have There is a substantial literature describing been able to select a number of genera or plant distributions in Malesia which we do not groups of genera that we believe to be mono- summarise here Instead we present distribu- phyletic and display distribution patterns of con- tions from a miscellany of fami- siderable biogeographic interest lies Firstly, two monocotyledonous families are We present examples from three subfamilies: discussed; from the palm family, generic distri- Nypoideae, and Arecoideae As butions within the three subfamilies Nypoideae, mentioned above, the last subfamily is probably Calamoideae and Arecoideae, and from the paraphyletic but the examples we have chosen grass family, distributions within the two bam- from within it are, we believe, monophyletic boo genera, Dinochloa and Nastus Secondly, in the dicotyledons, the genera Antidesma (Eu- phorbiaceae) and Elaeocarpus (Elaeocarpaceae) Nypoideae are considered The fern genus Christensenia () and a variety of other fern and This is the only subfamily in the Palmae repre- angiosperm examples from the diverse flora of sented by a single extant species Nypa fruticans New Guinea complete the assortment The term is distinguished from all other palms by a Malesia is used in this paper to identify the area number of unique features including the pros- bounded to the north by the Thai-Malaysian trate dichotomously branched stem, the erect border and to the south by the Torres Straits bearing a terminal head of pistil- (Steenis, 1950; Johns, 1995) It includes the fol- late , the lateral spikes of staminate flow- lowing political entities: Brunei Darussalam, In- ers and unusual features of the flowers them- donesia, , Papua New Guinea, Philip- selves (Uhl and Dransfield, 1987) Furthermore, pines and Singapore It is an area of exceptional the spiny zonosulcate grains are highly biological diversity distinctive With the exception of similar but much smaller and incompletely zonosulcate pollen produced by many species of the genus Palmae Salacca (Calamoideae), such pollen grains are not encountered elsewhere in the family, and The Palmae () are a diverse, largely are unknown outside the Palmae The pollen tropical and subtropical family of about 200 gen- grains are notably uniform in their morphology era and 2700 species In the latest classification throughout the geographic range of the genus of the family (Uhl and Dransfield, 1987) six sub- In a recent phylogenetic study of the whole fam- families are recognised The delimitation of ily, Nypa is resolved as sister taxon to all other these subfamilies is currently under rigorous palms (Uhl et al, 1995) phylogenetic analysis, and preliminary evidence Nypa fruticans is a mangrove palm, often suggests that four of the six (Coryphoideae, Ca- growing in vast natural stands in a variety of es- lamoideae, Nypoideae and Phytelephantoideae) tuarine conditions Its present day distribution are monophyletic whereas two, Ceroxyloideae extends throughout Malesia and also includes and Arecoideae, may be paraphyletic (Uhl et al-, Sri Lanka, the Ganges delta, Indochina, NW Aus- 1995) However, the relationships of many of tralia, the Solomon Islands and Ryukyu Islands the tribes, subtribes and genera within the sub- (Uhl and Dransfield, 1987) It has also been in- families need further study troduced to W and to Panama where it is The Malesian and W Pacific region represents now well established one of the richest areas of palm diversity in the Unlike its modern counterpart, fossil Nypa world An estimated 1000 species in 93 genera pollen, Spinizonocolpites (Muller, 1968), has are found in the area from Indochina to been shown to possess a range of spine lengths and the W Pacific islands of Fiji and New Cal- and spine distributions This variation has been edonia All subfamilies mentioned above are demonstrated by a number of authors to be very Malesian plant distributions 245

4 Ma

15 Ma

45 Ma

Fig!1 Distribution maps for Spinizonocolpites generated using Atlas palaeomapping program (Cambridge Paleomap Services, 1992), incorporated into Plant Fossil Record 22 (Lhotak and Boulter, 1995) 246 W- J- Baker et al-

Calamus Calospatha Retispatha

Fig!2 Distributions of genera in subfamily Calamoideae (Palmae), 

localised, often occurring in quite small matrix grains from offshore cores in the West Java Sea samples (e-g-, Harley et al-, 1991) The distribu- (R J Morley, pers comm, 1997) By the end of tion of Spinizonocolpites in the fossil record is the Miocene (Fig1A), the distribution did not remarkable (Fig1) It is known from the Upper extend far outside the area now occupied by Cretaceous (Senonian) of (Muller, 1968) Nypa fruticans There are few African records, although there is some doubt about the age of one or two unsubstantiated records in Europe, this record (Morley, 1998 this volume) Upper and there is a Pliocene record from New Zea- Cretaceous records are widespread throughout land (Couper, 1953) Records for India, Papua the palaeotropics, including Meso and northern New Guinea and SE Asia indicate a similar distri- S America, W and N Africa, the Middle East and bution to the early Miocene India From the Paleocene, northern palaeolati- tude records extend to c65oN, and include ex- amples from northern USA, Europe and Pakistan Calamoideae (Frederiksen, 1994) In the southern hemi- sphere, there are records of Spinizonocolpites in This large subfamily with 22 genera and 650 S Australia (Stover and Evans, 1973) and N Is- species is pantropic Three highly distinctive land, New Zealand (McIntyre, 1965) Eocene genera with palmate are confined to records are more frequent and by the Eocene northern S America Currently, they are regarded the widespread pantropical distribution was sta- as comprising a separate tribe, Lepidocaryeae, ble (Fig1C) There are additional records from but continuing studies have proposed stronger NW Australia (Hekel, 1972) and the Lower links with genera within the other tribe, Eocene of Tasmania, which is the most souther- Calameae, than had been suspected ly occurrence of Spinizonocolpites at palaeolati- In Africa, there are three endemic genera of tude 65oS (Cookson and Eisenack, 1967; Pole climbing palms (rattans) A fourth genus, and McPhail, 1996) For the Miocene (Fig1B), , is represented in Africa by a single records are substantially reduced There are species, but is extraordinarily diverse in Asia records from Africa, India and Malaysia, includ- The massive palm genus Raphia is very di- ing numerous and varied Spinizonocolpites verse in Africa One species extends to S Malesian plant distributions 247

Eleiodoxa Eugeissona Metroxylon Pigafetta Salacca

Fig!3 Distributions of genera in subfamily Calamoideae (Palmae), non-rattans and the rattan genus Korthalsia

America and another to Madagascar, but both certain genera which are almost exclusively these distributions are thought to be man-made Sundaic, but with local variations For example, All other calamoid genera are restricted to the Ceratolobus (6 species) is found in , Asian and W Pacific region where they display Java, Malay peninsula and Borneo Salacca varied distribution patterns (Figs2 and 3) How- (c20 species) is more widely distributed reach- ever varied these patterns may be, there is one ing China in the north and Palawan and conspicuous trend The greatest diversity in Mindanao in the east Plectocomiopsis (6 spe- terms of species and genera is overwhelmingly cies) is found in Sumatra, the Malay peninsula Sundaic rather than Papuasian The largest ge- (including S ) and Borneo, while nus Calamus, distributed from the W Ghats and closely related Myrialepis (1 species) occurs in China to Fiji and Australia and in Africa (1 spe- Indochina southwards to the Malay peninsula cies) and with a total of 370 species, is almost and Sumatra, but not Borneo or Java Eleiodoxa certainly paraphyletic (Kramadibrata, 1992, (1 species) is restricted to peat-swamp in Baker unpublished), but even when the distri- the Malay peninsula (including S Thailand), butions of individual, potentially monophyletic Sumatra and Borneo (see also Cyrtostachys be- groupings within the genus are examined, there low) Pogonotium (3 species) is confined to pe- is a similar bias of diversity in Sundaland The ninsular Malaysia and Borneo, while Calospatha genera Korthalsia with 26 species of climbing (1 species) is endemic to peninsular Malaysia palms and Daemonorops with about 115 species and Retispatha (1 species) to Borneo These lo- are two other examples of genera with major cal distribution patterns within Sundaland em- diversity in Sundaland and with a decrease in phasise the close relationship of the floras of number of species eastwards The distribution of these land masses Differences may be explica- these genera strongly suggests a south-east- ble in terms of vegetation changes in relation to wards invasion from Sundaland to Papuasia that climatic fluctuations and chance dispersal and could have occurred after the Miocene juxtapo- extinction events sition of the two ends of Malesia (but see also Eugeissona (6 species), distinguished by a Morley, 1998 this volume) large range of unique characters but still clearly A further type of distribution can be found in a member of the subfamily, is distributed in the 248 W- J- Baker et al-

Malay peninsula and Borneo Two fossil paly- New Guinea (Fig4A) This remarkable genus nomorphs of lower and middle Miocene age in deserves a modern phylogenetic study Borneo have been referred to Eugeissona sug- Veitchia with about eighteen species belongs gesting the presence of the genus in Borneo to subtribe Ptychospermatinae This subtribe is from at least the early Miocene Fossil pollen, defined by a suite of presumed apomorphies Quilonipollenites, of Lower to Middle Miocene unusual within the  Intergeneric rela- (21-14 Ma) age from India (Muller, 1972, 1979; tionships are currently being reassessed by Scott Morley, 1977; Phadtare and Kulkhani, 1984) has Zona at Fairchild Botanic Garden; while the lim- also been referred to Eugeissona (see also Morley, its of Veitchia may be uncertain, there seems no 1998 this volume) doubt that the subtribe itself represents a mono- There are two highly distinctive genera which phyletic group Veitchia is present in Fiji (10 do not display the Sundaic bias Metroxylon, the species) and Vanuatu (5 species) A single spe- sago palm, with five species, is found in the cies (V- merrillii) is restricted to karst limestone Caroline Islands, Fiji, Vanuatu, the Solomon Is- in Palawan and neighbouring islands (Fig4A) lands, the Bismarck archipelago and New This is an extraordinary disjunction Even if the Guinea M- sagu, now widely dispersed by man limits of Veitchia are changed, the presence of across Malesia as a starch-producing crop, is this species in Palawan is still remarkable, as the thought to be native to New Guinea The other rest of the members of the subtribe are found genus, Pigafetta, with two species of massive only in Maluku, New Guinea, Australia and W pioneer tree palms, is represented in Sulawesi Pacific islands by P- elata and in Maluku and W New Guinea Rhopaloblaste (subtribe Iguanurinae), a mor- by P- filaris Both species of Pigafetta, possess- phologically remarkably uniform genus that we ing relatively very small , produced in regard as being natural, also displays unusual large quantities, are apparently efficient colonis- disjunction One species is present in the ers of open habitats within their range so it and one in peninsular Malaysia seems surprising that the genus is not more while the other four species are found in widespread than it is That these two genera are Maluku, New Guinea and the Solomon Islands so distinct from other Asian calamoids both in (Fig4B) their morphology and their distribution is clearly Cyrtostachys (sole genus of subtribe Cyrto- suggestive of a very different biogeographic his- stachydinae) has a single species, C- renda, tory from the other calamoid genera widespread in peat-swamp forest in Sumatra, Current molecular and morphological work is Malay peninsula and Borneo, while the seven providing exciting new insights into the generic remaining species are restricted to New Guinea, relationships within the Calamoideae (Baker et the Bismarck archipelago and the Solomon Is- al-, 1998; Baker and Dransfield, unpublished lands (Fig4C) Pollen referred to Cyrtostachys work) A robust phylogeny of the Calamoideae occurs in Upper Miocene deposits in Borneo will be a powerful tool in biogeographic studies (Muller, 1972) of SE Asia

Gramineae Arecoideae The genera Dinochloa and Nastus are members As stated above, this very large subfamily may of the tribe , the woody prove to be paraphyletic We have chosen four (subfamily Bambusoideae, family Gramineae) unusual examples from tribe Areceae, a tribe Phylogenetic relationships within the tribe are which, while being pantropic, is most diverse in not yet understood and are currently being in- the W Pacific In marked contrast to the vestigated, but at present it is divided into 8-9 Calamoideae, the tribe displays greatest diver- subtribes (Soderstrom and Ellis, 1987, Dransfield sity at the Papuasian end of the Malesian region, and Widjaja, 1995) These two genera have been with only a few genera (e-g-, , Nenga chosen to illustrate the widely differing distribu- and Iguanura) displaying a Sundaic bias tions that occur within the Bambuseae Orania with about twenty species is the sole Dinochloa is a natural, well-defined genus of member of subtribe Oraniinae There are three 23-39 species, each with a limited distribution It species in Madagascar, one in the western part is placed in the , a subtribe with a of Sundaland, three or four in the Philippines, largely tropical Asian distribution which is most one in Maluku, one in Aru Islands and nine in diverse in tropical mainland Asia The genus it- Malesian plant distributions 249

A Veitchia Orania

B Rhopaloblaste

C Cyrtostachys

Fig!4 Distributions of genera in subfamily Arecoideae (Palmae) A: Orania and Veitchia, B: Rhopaloblaste, C: Cyrtostachys 250 W- J- Baker et al-

Dinochloa Nastus

Fig!5 Distributions of genera in subfamily Bambusoideae (Gramineae), Dinochloa and Nastus

self is found mainly in Malesia where it occurs in cific Islands and from the Himalayas to N Aus- Sundaland, the Philippines, Sulawesi and Flores, tralia The highest diversity, both in species but it also extends to the Andaman Islands and number and character variation, exists in peninsular Thailand (Fig5) It is absent from Malesia, where about 90 of the 150 currently Maluku eastwards Clearly, Dinochloa is a genus recognised species occur, c70 of which are en- with a strongly Sundaic distribution Given the demic to the region (Fig6A) Despite the large limited distribution of the majority of its mem- number of species, no subgenera or sections can bers, a phylogenetic analysis could be biogeo- be recognised within Antidesma, and the great graphically informative variability in some species complexes suggests The genus Nastus is included in subtribe that speciation is actively taking place Nastinae, which contains genera distributed in The genus Antidesma belongs to the subtribe the southern hemisphere of the Old World Antidesminae, the most notable character of tropics The genus comprises about 19 species, which is the enlarged, U-shaped connective of distributed from Reunion and Madagascar to the anthers that is found nowhere else in the Java, Sumba through New Guinea and Solomon family The unilocular and highly reduced Islands, and possibly in Sumatra (Fig5) This flowers of Antidesma suggest that the genus is disjunct distribution is remarkable and parallels monophyletic Furthermore, the genus is the to some degree that of the palm genus Orania only representative of the subtribe in Asia Its However, Nastus remains a poorly known genus closest relative Hyeronima occurs in S America and the Caribbean, while the genus with the largest number of ancestral character states in Antidesma (Euphorbiaceae-Phyllanthoideae) the subtribe, Thecacoris, is distributed in Africa and Madagascar This strongly suggests that the Antidesma, a genus of dioecious and subtribe and the genus Antidesma have origi- , is commonly found in the understorey of nated in Gondwana, although no confirmatory the tropical rain forest It is distributed through- fossil evidence has yet been presented out the palaeotropics from W Africa to the Pa- The distribution data presented below have Malesian plant distributions 251 been taken from a forthcoming revision of the has a similar but slightly more northwestern dis- genus in western and central Malesia tribution (Malay peninsula, Sumatra, W Java, (Hoffmann, unpublished work) Borneo, Philippines and N Sulawesi) with more humid conditions

W and S Malesian elements Species extending across the Isthmus of Kra The majority of species fall into this category Examples of species endemic to one island in- Several species do not respect the demarcation clude A- brachybotrys (E Sarawak and Brunei line between Malaysia and SE Asia slightly north Darussalam), A- montis-silam (), A- ortho- of the Thai-Malay border (Steenis, 1950), e-g, A- gyne (Malay peninsula) and A- pleuricum (Phil- puncticulatum (Fig6C) and A- velutinosum ippines) Other species are common to more (Burma, Thailand, Malay peninsula, Anambas than one island, e-g-, A- tetrandrum (Sumatra, and Natuna Islands, Sumatra, Java) A- japoni- Java and Bali), A- pendulum (Sumatra, Borneo cum (peninsular Malaysia, Thailand, Burma, In- and Malay peninsula) and A- leucopodum (Su- dochina, SE China, S Japan, Taiwan, Luzon) is matra, Borneo, Malay peninsula and Mindanao: an example of the similarity of the upland flora Fig6B) The Philippines show the highest de- of N Luzon and E Asia (Steenis, 1950) gree of endemism, followed by Borneo and the Malay peninsula In Antidesma there is no sharp boundary be- Monsoon forest elements tween the W and the S Malesian province of Steenis (1950) A- tetrandrum for example oc- A- acidum (syn A- diandrum) is the only spe- curs in Sumatra, Java and Bali, while its pre- cies in the genus with a disjunct distribution sumed sister species A- venenosum is common (Fig6D) This disjunction is known from many throughout Borneo A- minus, a species com- other taxa including the teak tree, Tectona mon to the submontane regions of Java and grandis (Verbenaceae) A- acidum is found in Sumatra, illustrates Steenis’ statement about the the teak of Java and listed among the similarity of the mountain flora of Java and that drought indicating plants (Steenis and of most of Sumatra Furthermore, the two spe- Schippers-Lammertse, 1965) The species is also cies extending across the Makassar Straits, A- somewhat isolated morphologically stipulare and A- tomentosum (see below), occur The taxa sharing this distribution pattern re- in W Malesia and Java but not in the Lesser quire a two-seasonal climate with an annual Sunda Islands drought period They are present in the monsoon forests of Burma, Thailand and Indochina, avoid the everwet central part of W E Malesian elements Malesia from the Isthmus of Kra southwards, but reappear in Java, parts of the Philippines, In his account of the Euphorbiaceae of New Sulawesi and the  Because Guinea, Airy Shaw (1980) recognised 32 species of the high number and the composition of taxa on the island, 27 of which he reported to be concerned, this cannot be explained by anthro- endemic As most of them are poorly known at pogenic dispersal only Instead, it dates back to the moment, these figures might change with a the extension of areas with periodical drought critical revision A- excavatum (syn A- molucca- during the Pleistocene, which then disappeared num) is the only E Malesian species with a wide again in the post-glacial period leaving many distribution It is common to N Sulawesi, taxa with disjunct distribution areas This has Maluku, New Guinea, the Admiralty and Solo- been discussed in detail by Steenis (Meeuwen et mon Islands (Fig6B) al-, 1960)

Species extending across Makassar Straits Widespread species with a broad ecological spectrum The distribution of A- stipulare bridges the phyto- geographic demarcation line of the Makassar The three most widespread Asian species hardly Straits (Steenis, 1950), including comparably dry show any ecological preferences This applies Maluku and S Sulawesi (Fig6B) A- tomentosum particularly to the very common A- montanum, 252 W- J- Baker et al-

A

50 2

90

10

5 7

B

A. stipulare A. excavatum A. leucopodum

C D

A. puncticulatum A. acidum

Fig!6! Distributions in the genus Antidesma (Euphorbiaceae) A: worldwide distribution of Antidesma (numbers indicate the number of species in the outlined areas); B: A! stipulare and A! excavatum, A! leucopodum; C: A! puncticulatum; D: A! acidum Malesian plant distributions 253 which occurs in most habitats from India (ex- Australia do not fit into the otherwise effective cluding Sri Lanka) to S Japan, Indochina, the classification within the genus Preliminary Philippines, W Malesia, Java and Sulawesi A- analysis (Coode, 1987) supports the suggestion ghaesembilla is found throughout the region in- that the family has undergone a major radiation cluding India, S China, New Guinea and N Aus- in the Australian region, certainly in Gondwana tralia It is the only species in the genus that pre- although, of course, the number of taxa in an fers open vegetation such as secondary scrub area does not necessarily indicate that the group and savannah A- bunius is widely cultivated as has evolved there Furthermore, the family “is a tree, which makes it impossible to estab- represented in the Tertiary fossil record in lish its original distribution The species is Australia by pollen, leaves and fruit” while fruits known from Nepal and Sri Lanka to the Philip- identifiable as belonging to Elaeocarpus have pines and Maluku, although no collections from “been recognised as a ubiquitous element of the the Malay peninsula have been seen Tertiary ” (quotes from It has been shown for many plant taxa that Rozefelds and Christophel, 1996) Rozefelds and the ecological amplitude and geographic distri- Christophel also quote references reporting bution of polyploids may exceed that of related fossil wood from the Tertiary in India and the diploid taxa (Briggs and Walters, 1984, Paleocene in Patagonia Skalinska, 1946) According to the chromosome Elaeocarpus is a genus of some 360 species numbers compiled by Hans (1970, 1973), three distributed widely in the Old World tropics, but African species and the two Asian species A- not in Africa It is currently known from the area ghaesembilla and A- acidum are diploid with n bounded by Madagascar, eastern India includ- = 13, which is the base number in most Phyll- ing Ceylon, the warmer parts of China and Ja- anthoideae On the other hand, A- acuminatum pan, New Caledonia, eastern Australia, New (A- montanum-complex) and A- bunius have Zealand, the western Pacific and  The been found to be polyploid In the former spe- majority of the species occur in SE Asia, Malay- cies both diploid (n = 13) and hexaploid (n = 39) sia, the Philippines, Indonesia and New Guinea races have been observed, whereas A- bunius Many species appear to be successional while has been shown to be 18-ploid (n = 117) All others are restricted to the forest depths They polyploid records are based on collections from occur from sea-level to 3000 m or more India, where the genus reaches its northern Although formal analysis is lacking, several limit, and both taxa are among the most wide- groupings within the genus Elaeocarpus are al- spread, variable and ecologically tolerant taxa most certainly monophyletic The distribution A possible evolutionary scenario based on the patterns of four of these groupings are present- facts presented here would suggest the origin of ed Unfortunately, the large and widespread the genus in wet tropical eastern Gondwana, groups (currently known as section Coilopeta- followed by migration to and extensive radia- lum and section Monocera) cannot be discussed tion in tropical Asia Climatic changes during the as it is doubtful that they are monophyletic Pleistocene affected the disjunct distribution of Section Elaeocarpus is most speciose in the A- acidum (see above) Unfortunately, we have western part of its range, tailing off eastwards no means yet to date any of the other events after Borneo (Fig7A) There is evidence of fur- The most promising systematic approach to ther speciation in New Guinea, with two small render this outline more precise would involve groups of species, one endemic, the other not an extensive survey of chromosome numbers in found west of Sulawesi, in addition to the wide- the genus and analysis of molecular data spread E- solomonensis In Fig7B the Polystach- yus group presents a different pattern Also in- cluded in Fig7B are the hypothesised nearest Elaeocarpaceae relatives to the Polystachyus group, which are in Sulawesi and Australia (Coode, 1997) The Elaeocarpaceae are a mostly tropical family The Acronodia group has a rather similar pat- of some 500 species, the majority of which are tern of current distribution (Fig7C) but appar- trees Six of the family’s nine genera ently its closest links are with China and Mada- (Aceratium, Aristotelia, Dubouzetia, Elaeo- gascar (Coode, 1996) Section Oreocarpus in- carpus, Peripentadenia and Sloanea) occur in cludes a single species (Elaeocarpus culminico- Australia which therefore has more genera of la) found in various forms from the Philippines, Elaeocarpaceae than any other land mass Sulawesi, Maluku, New Guinea and the Bis- Furthermore, several species of Elaeocarpus in marck archipelago, Aru Island, Melville Island 254 W- J- Baker et al-

Section Elaeocarpus A

B The Polystachyus group Nearest relatives

C Section Acronodia E. culminicola

Fig!7! Distributions in the genus Elaeocarpus (Elaeocarpaceae) A: section Elaeocarpus; B: the Polystachyus group and its hypothetical nearest relatives; C: section Acronodia and E! culminicola Malesian plant distributions 255 and NE (Fig7C) The six remaining Cephalomanes boryanum occurs on Manus, species of the section are all found in Australia New Ireland, the Solomon Islands, Woodlark Is- alone land, the Louisiade archipelago and on the mainland of SE Papua

Curious plant distributions in Papuasia Discussion Some curious distributions of and angiosperms have been selected as evidence for At this stage, it would be inappropriate to specu- relationships between certain land masses and late on the geological significance of the data parts of Papuasia Such evidence carries a caveat presented here Any one explanation of these that the plant collection density for New Guinea very preliminary data could easily be replaced is particularly low (Johns, 1995) by another interpretation while formal analysis Christensenia, a fern genus in the Marattiaceae, is lacking A few generalisations can be made comprises a single species, C- aesculifolia, dis- Firstly, we believe that the distributions that we tributed from India and SE to Malesia have discussed probably require a tectonic ex- and the Solomon Islands (Camus, 1990) With planation This seems to be particularly true for the exception of a single collection from the the curious disjunctions that have been dis- Vogelkop peninsula in Irian Jaya, this species cussed, such as those found in Orania and has not been recorded from the mainland of Nastus between Malesia and Madagascar, and in New Guinea Within Papuasia the genus occurs Rhopaloblaste and Cyrtostachys between E at several sites on New Ireland and in the Solo- Malesia and W Malesia However, it is important mon Islands to be aware of the potential impact of extinction The Vogelkop peninsula includes several in generating apparently disjunct distributions other floristic elements which it shares with cen- which at one time may have been continuous tral and western Malesia, but not with the re- Furthermore, we find it far easier to explain W mainder of New Guinea The dipterocarp Hopea Malesian plant distributions than those of E inexpecta (Hopea Section Dryobalanoides), the Malesia as the geological evolution of the former only representative of this section east of region is better understood We anxiously await Wallace’s Line, is restricted to the Kebar Valley the elucidation of the geological evolution of E in the Vogelkop where it is locally frequent in Malesia, especially of the Papuasian region lowland rain forest The rubiaceous plant Although dispersal events are of no interest to genus Myrmephytum is represented in the Phil- vicariance biogeographers, they are a biological ippines, Sulawesi, Maluku and by five species in reality It is important to take dispersal into ac- the Vogelkop peninsula count when one is considering biogeographical Distribution patterns also suggest a relation- patterns of a single group in isolation from other ship between western and central Malesia, the groups so as to avoid mistaking ecological noise Bismarck archipelago and the Solomon Islands, for biogeographical signal One of our exam- excluding New Guinea Several other distribu- ples, the distribution of Antidesma, is thought to tions support this suggestion The genus be heavily influenced by long distance dispersal, Sararanga () occurs in the Philip- as the small bright red or black fruits are attrac- pines (S philippinensis), and is represented by a tive to birds Therefore, it is likely that the distri- second species (S- sinuosa) along the island arc bution of many Antidesma species is a reflection to the north of New Guinea It is found also on of their climatic, altitudinal and edaphic prefer- Manus Island and New Ireland in the Bismarck ences rather than of tectonic movements archipelago and throughout the Solomon Is- The efficiency of birds in long-distance plant lands with three small localised populations dispersal is difficult to assess, as a number of known from the north coast of New Guinea on factors must be taken into account, such as the Japen Island, near Jayapura and Vanimo A simi- retention time of the in the digestive sys- lar pattern is also shown by the ferns Pneuma- tem and the viability of the transported seed af- topteris rodgersiana and Christella harveyi ter defecation or regurgitation Both depend on Some species which reflect this pattern of dis- the characteristics of the seed (e-g-, attractive- tribution also occur on the New Guinea main- ness and nutrient content of the fruit pulp or aril, land in SE Papua, suggesting an additional rela- seed size and robustness) as well as the bird tionship between the Solomon Islands and the (e-g-, size, presence of grit in the muscular giz- Papuan peninsula For example, the fern zard, flight speed, territorial behaviour) For ex- 256 W- J- Baker et al- ample, some birds may avoid open spaces to in Malesian plant groups may be found in Linder avoid potential attacks by predators, thereby and Crisp (1995), Turner (1995) and Ridder-Nu- failing to deposit seeds in these habitats, while man (1996) other birds may cross open areas flying at high SE Asia contains a diverse flora which un- altitude and act as effective dispersal agents for doubtedly reflects its complex geological his- seed The major difficulty lies in the fact that tory When rigorous systematic methods are ap- most studies necessarily concentrate on only plied to the members of this flora, further pat- one aspect of this complex process, usually ei- terns may be revealed and related to tectonic ther the behavioural patterns and physiology of evolution Preliminary discussions such as ours a particular bird taxon or the dispersal type of are necessary to assess the potential value of the plants found in a certain ecosystem groups in biogeographical studies A recent project on forest regeneration on Krakatau investigates the re-colonisation of the once sterilised islands by bird-dispersed plants Acknowledgements (Whittaker and Jones, 1994) Three or four spe- cies of Antidesma have arrived on Krakatau so The authors would like to thank Terry far A- montanum, the most common and most Hedderson, Anne Bruneau, Estrela Figueiredo, widely distributed species of the genus, has be- Sasha Barrow, Freek Bakker, Joe Mullins, Peter come the dominant element of the forest Stevens and an anonymous reviewer for helpful understorey (Whittaker and Schmitt, pers comments on the manuscript and Chris comm, 1997) However, as Krakatau is only 40 Humphries for valuable advice km away from the nearest mainland, the disper- sal of seeds across greater distances may follow different rules References Robust biogeographic hypotheses could be constructed from the data presented in this pa- Airy Shaw, H K 1980 The Euphorbiaceae of New Guinea per if the examples used were taken further into Kew Bulletin Additional Series 8: 1-243 the analytical phase, historical biogeography Baker, WJ, Dransfield, J, Harley, MM and Bruneau, A Historical biogeography can be practised on dif- 1998 Morphology and cladistic analysis of the subfamily Calamoideae (Palmae) Memoirs of New York Botanical ferent levels A simple approach is to discuss the Garden, in press biogeographical implications of a single group, Ball, I R 1975 Nature and formulation of 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