Botanical Journal of‘tke Linnean Socie<v (1982) 85: 133-146. With 5 figures

Pandanus tectorius Parkins. in Australia: a conservative view

BENJAMIN C. STONE

Herbarium, Department of Botany, University of Malaya, Kuala Lumpur, Malaysia

Receiiied June 1980, acctpted f o r publkafion Fehrua!y 1982

Pandanus frdorius Parkins. is a widespread and variable species with many forms, often local, some of which have been considered as distinct species. Fourteen binomials are here considered as synonyms of P . tecforius, but several of them warrant retention at varietal rank. Comments on the variability and its relation to .I species concept in the genus Pandanus are included.

KEY WORDS:-Australia - Pandanaceae ~ Pandanu - P. f ec for iu - taxonomy - variability.

CONTENTS

Introduction and taxonomic background . . . . . . . . . . . . 133 Taxonomy of Pandanus tecforiu in Australia . . . . . . . . . . . . 136 Australian varieties of Pandanus fvcforius . . . . . . . . . . . . . 136 Variability in the populations . . . . . . . . . . . . . . . 140 Character convergence between some species of Pandanus section Pandanu and section

Ausfrok~ura in Australia . . . . . . . . . . . . . . . . 145 References. . . . . . . . . . . . . . . . . . . . 146

INTRODUCTION AND TAXONOMIC BACKGROUND

For a long time, Pandanuspedunculatus R. Br., which was one of the first species of the genus to be described from Australia, has been retained as a separate entity from Pandanus tectorius Parkins., originally described earlier from Tahiti. Warburg ( 1900 : 46) maintained P. tectorius in its broadest sense on taxonomic grounds, yet excluded P. pedunculatus although he remarked “Species vix a P. tectorio df lere videtur, a quo drupis profunde sulcatis solum distingui potest, character in P . tectorio variabili“. Strangely, Warburg made P. spiralis R. Br. a synonym of P . tectorius, and thus, probably on this basis, he included “Tropisch Australien” in the distributional range of the latter species. Nonetheless, i t is his broad concept of P. tectorius which I accept here, although certainly P. spiralis and some other taxa, synonymized by Warburg (particularly those equivalent to P. odoratissimus L.f.) are excluded. Subsequently, Martelli (1913, 1914) accepted P. pedunculatus and P. spiralis as distinct from P. tectorius, although his concept of the latter differed from that of Warburg. In addition Martelli changed his opinion more than once conterning the status of P . odoratissimus L. fil. in relation to P. tectorius; at first he

19.3 0024-4074/82/060133+ 14 S03.00/0 0 1982 The Linnean Society of London

134 B. C. STONE

used the latter name for a broad species concept, and created varieties within it, of which one was called P . tectorius var. australianus Martelli. This plant represents P . tectorius as conceived by Warburg and by myself. Later, Martelli (1930) treated P . tectorius as a synonym of P. odoratissimus. Yet, throughout his career, Martelli also continued to discriminate taxa (both at species and varietal rank, as well as formally named species which he described as “microspecies” (Martelli, ,.1933 : 150), chiefly from Polynesia, for example P. macfarlanei, P. prismaticus, P . raiijavaensis, P . upoluensis, etc.

As I have previously pointed out at length (Stone, 1976: 60) Martelli saw no wild pandans in their native habitats and employed an idiosyncratic typological method. Since Martelli’s work there have been further nomenclatural vicissitudes. The difficulty in accepting the species names published by Parkinson has now been resolved (St John, 1972; Stone, 1976). In the first edition of Parkinson (1773) all the species names were effectively monomials, hence illegitimate, owing to the use of connecting hyphens; but in the German edition, edited by ‘Z’ (1774) no hyphens were used and thus the names were legitimate binomials. (Recently, Degener has identified the person ‘Z’ with Johann Philipp du Roi, 1741-1785; Degener & Degener (1981) have proposed a new combination P . tectorius (‘J. P. du Roi) Deg. & Deg., which is neither necessary nor possible.) At any rate P. tectorius Parkins. ex ‘Z’ is now widely agreed upon as an accepted binomial. It is the purpose ofthis review to indicate that the broader species concept of Warburg, and of the earlier phase of Martelli, should be revived in a modified form, and that P. tectorius occurs in Australia in several varieties and forms, one of which is that which R. Brown named P. pedunculatus, and that several recently proposed species should be reduced to synonymy or to a minor taxonomic rank under P. tectorius. The neutral concept of the botanical varietas is useful to designate striking and unusual forms of this species.

The idea that P . pedunculatus and P. tectorius are equivalent, or mere forms of one species, is not new; Domin (1915) first made the appropriate varietal combination. However there is very little difference between P. tectorius var. pedunculatus (R.Br.) Domin and P. tectorius var. australianus Martelli (1914). They seem to differ only in some features of the phalanges, such as the smooth, non-sulcate lateral faces ofvar. australianus which contrast with the shallowly-furrowed, intercarpellary sutures of irregular length which break up the lateral faces of the phalanges into partial or segmental faces in P. tectorius var. pedunculatus.

Martelli (1913) conceived of P. pedunculatus in a rather restricted sense, which I have followed in earlier studies (Stone, 1972, 1973). However, the type of P.pedunculatus was recently studied by St John ( 1968) who pointed out that Martelli’s illustration of the Australian member of this species was not the type specimen. St John does not consider that specimen illustrated by Martelli (a collection by F. v. Mueller) as pertaining to the species P. pedunculatus, and to the extent that it does not appear to be consistent with Brown’s concept of the species, this is correct. Nevertheless, I believe that Martelli was correct in his conclusion that there were related taxa or forms which occurred in Australia and in other areas especially in the Pacific (Stone, 1976). The distribution of P. tectorius is by means of ocean currents which carry the floating phalanges, and therefore wide distributions should not be surprising.

In recent years St John (1962, 1967, 1968, 1969) has described many new

P.4 10.4 \I'S IN AL'STR4LI.A 135

Pandunus species from Australia. Some of these can, I believe, be more or less readily subsumed u ithin Pundunus tfctorius as straightforward synonyms. The biology of the maritime pandms suggests strongly that an extremely narrow species concept is inappropriate; i t cannot be applied to most plant species of t h e Indo-Pacific strand flora. More important is the fact that with such a narrow species concept, only mature pistillate collections can be identified, while staminate specimens are unidentifiable. Any insistence on exact identity, rather than fundamental similarity, in the characters of the phalanges, leads to the attempt to discriminate too many entities as species.

The \xiability in the fruit of Pandanu3 trctoiius (as here broadly construed) is considerable; and the mechanisms which underlie this \fariation will affect taxonomic concepts. G'pnrtic control: The growth dynamics of the fruit is an important source of variation. If many genes are involved, and if these are represented by several or many alleles, there will potentially be continuous variability in fruit characters. If simple Mendelian changes haire substantial effects i t may be that some \rery striking differences will prove to be comparatively insignificant. Hyvbrzdiiation : In general, hybridization of P . tfctorius with other (conservatively recognized) species is theoretically possible. Since there are no experimental studies of the matter, and almost no discussion of the subject in the literature, little more can be said. I n Australia P. tectorius appears to be the only species present of Pandanus section Pundanus; the other Australian species which belong to Pundanus subgenus Pandanus f i l l under different sections. Other species of Pundunus section Pandanus occur in New Guinea, the Solomon Islands, Micronesia, Western hlalesia, as far west ds East Africa. Hybridization of P. ttclorius with P. odoratissimus is suspected but not proved. Unless hybrids can result from crosses of plants representing different generic sections interspecific hybridization would not occur in the Australian populations of P. tectorius. :lpornzxis: Several different means of vegetative propagation are known to occur in the genus Pandunus. In the Queensland species P. gemmifer St John. (Pandunus section .4ustrafibrassia St John) bulbils occur on the stems and branches even on fruit- hearing pistillate plants. The same situation has been seen in P. kuruku Martelli, a Madagascar species (Stone, unpublished). These bulbils form from axillary buds and produce a small leafy shoot which eventually drops to ground and takes root. Though all pandan species are dioecious, the formation of viable seed is not proof of fertilization. In the large maritime pandan P. dubiuJ Spr. (not found in Australia) apomixis almost certainly occurs, although the evidence is circumstantial (Kurz, 1867; Fagerlind, 1940a). Embryology in some Pundanus species is complicated by the appearance of supernumerary nuclei in the embryo-sac; these have been shown to be derived from the inward migration of nuclei from the surrounding nucellus (Fagerlind 1940a ; Cheah & Stone, 1975). Fagerlind ( 1940b) reported complete parthenocarpy in P . columnaeformis Fagerl., a phenomenon which could indicate apomixis. Nuclear migration might enable agamospermy to occur, as was suspected in P. jygmueus Thou. by Solms-Laubach (1878). Apomixis will have an effect on classification, particularly if clonal apomicts become persistent elements in vegetation, a situation by no means unfamiliar. The obvious taxonomic difficulties in certain species-groups of Pundunus such as the 'P. tectorius-group' and also in Pandunus section Austrokeuru Stone, may be caused by apomixis.

136 B. C. STONE

TAXONOMY OF PA.NDA.NlJS TECTORIW IN AUSTRALIA

Pandanus tectorius is here considered as a widespread species, found in many places outside Australia, and variable both within and outside Australia. To focus attention on variation, varieties of the species are denominated, but there is no implication that these are all of equivalent status in a biological sense. A variety may be a striking but ephemeral apomictic clone, a rare polyploid, or a local geographical ‘race’ and some may, when they are better understood, be subsumed in formal nomenclature, while others may be ranked as subspecies. In my opinion none of them is a good, biologically defined species.

Until the establishment ofa standard (fruiting) specimen it will not be possible to distinguish all those varieties mentioned whose characters depend upon the fruit. It is possible that the staminate plants of these varieties will not have identifying characteristics; such varieties therefore would exist only in the pistillate form. Whether such a situation is permissible nomenclaturally and taxonomically is a moot point. However, it should be pointed out that the paucity of staminate collections makes it possible that staminate characters may have been neglected. An analogous situation occurs in the taxonomy of some insect groups, in which male genitalia provide the sole identifying features for species.

AUSTRALIAN VARIETIES OF PA.VDA.NUS TECTORICIS

Pandanus subg. Pandanus sect. Pandanus, sensu stricto

Pandanus tectorius Parkins., Journal of a V y a g e to the South Seas in . . . H.M.S. Endeavour (1773), nomen jugaturn; idem. ed. ‘Z’ (transl., = J.P. du Roi?) in Der Naturforscher, 4 : 250 ( 1 774), nomen normale non-jugatum descriptioque. TYPE: Tahiti; immature pistillate inflorescence and portions of two leaves; drawing of staminate inflorescence; Society Islands, 1769, Banks and Solander (BM). St John, Botanical Journal of the Linnean Society, 4 : 309 (1972) ; PaciJic Science, 33: 395 (1980). Stone, Kew Bulletin, 32: 60 ff. (1976).

Botanical usage of this name has been so loose that full synonym citation here would serve no purpose, hence only those synonyms for Australian provenience are listed.

P . pedunculatus R. Br. Prodromus: 341 ( 1810). Bentham, Flora Australiensis, 7 : 149 ( 1878). Bailey, Queensland Flora, 5: 1689 ( 1902). Warburg, Das Pjanzenreich, 3, ZV. 9: 46 (1900). St John, PaciJic Science, 22: 418, f. 271 (1968). TYPE: Australia: Queensland, Hervey’s Bay, Sandy Cape (i.e. northern tip of Fraser Island), R. Brown 5799-A (BM), emended by St John to a single phalange.

P . odoratissirnus sensu Bentham, Flora Australiemis, 7: 148 (1878) non L. fil.; et sensu Bailey, Queensland Flora, 5: 1689 ( 1902), non L. fil.

P . blakei St John, Pa& Science, 26: 156, f. 110 (1962). TYPE: Australia, Queensland, Yule Point 27 mi. N. of Cairns, St John 26260 (BISH).

P . oblatiapicalis St John, Pacijic Science, 26: 310, f. 117 (1962). TYPE: Australia, Queensland, Green Island off Cairns, St John 26267 (BISH) .

P . sinuvadosus St John, Pacijic Science, 26: 329, f. 127 (1962). TYPE: Australia, Queensland, Green Island off Cairns, St John 26268 (BISH).

SYNONYMS :

P,4 VD.4.C‘I ‘S IN ACSTRALIA 137

P. viridinsularis St John, PaciJic Science, 16: 339, f. 136 (1962). T Y P E : Australia, Queensland, Green Island off Cairns, St John 26270 (BISH).

P. yorkensis St John, Paczfc Science, 16: 344, f. 137 (1962). TYPE: Australia Queensland, Cape York, Newcastle Bay, Brass 18787 (BRI).

P . adscendens St John, Pacific Science, 21: 527, f. 242 (1967). TYPE: Australia, Queensland, Green Island off Cairns, St John 26266 (BISH).

P . brownii St John, PaciJic Science, 22: 416, f. 270 (1968). TYPE : Australia, “northern or north-eastern Australia, locality unknown” R . Brown Iter Australiense 1802-5

P. bowenensis St John, Paclfc Science, 23: 97, f. 285 (1969). TYPE: Australia,

P. extralittoralis St John, Pacific Science, 23: 101, f. 287, 288 ( 1969). TYPE : Australia,

P. hubbardii St John, PaciJic Science, 23: 104, f. 289 (1969). TYPE: Australia,

P. stradbrookeensis St John, Pa@ Science, 23: 92, f. 282, 283 (1969). TYPE: Australia,

P . heronensis St John, Pacijc Science, 23: 89, f. 281 (1969). TYPE: Australia,

P. terrireginae St John, Pacific Science, 23: 114, f. 294 (1969). TYPE: Australia,

(BM).

Queensland, North Kennedy District, Bowen, Blake 18559 (BRI).

Queensland, Heron Island, Poulsen in Blake 20375 (BRI) .

Queensland, Stradbrooke Island, Hubbard 2238-i1 (K).

Queensland, Stradbrooke Island, Moreton Bay, W h i t e 3387 (BRI).

Queensland, Great Barrier Reef, Heron Island, Thorne 17215 (BRI).

Queensland, Port Danger, Osborn s.n. (AD).

Pandanus tectorius Parkins. var. australianus Martelli, Webbia, 4: 33 (1913) nomen; 4: tav. 18, f. 1-3; 409, descrijltio (1914). TYPE: Australia, in Herb. Martelli (FI) ex Herb. Melbourne (s ic!) .

Phalange sides smooth, unsutured; phalanges 60 x 35-50 mm, obpyriform; carpels 8-12, tips low convex; phalanges very low convex to subtruncate but not abruptly

SPECIMEN EXAMINED : Australia : New South Wales ; Pottsville, between Tweed Heads and Cape Byron, rocky headland, 22 March 1961, W. G. Jones s.n. (BRI). A quite reasonable match for Martelli’s figure, but not really very different from some forms of P. tectorius var. stradbrookeensis.

Although the type locality is unknown it is likely to be somewhere on the east Queensland coast or on one of the numerous offshore islands. The same variety is reported from the New Hebrides and Fiji (Stone, 1976) and is probably to be found scattered throughout parts of Melanesia and western Polynesia.

so.

Pandanus tectorius Parkins. var. incrassatus Stone, K e w Bull., 31: 66 f. 4D. (1976). TYPE: Stone 2227 (BISH) from Pwele Island, New Hebrides. Phalanges rather large, c. 70 x 50 mm, apex truncate, carpels about 9, their tips broadly pyramidal 4-6 mm tall. SPECIMENS EXAMINED : Australia ; Queensland ; Moreton District ; Barleigh Heads, sea cliff, lorn alt., 16 June 1966, Blake 22747 (BRI)! - Wide Bay Distr., near Noosa Head, along shore in shingle and on cliK 2-30 m, 21 August 1956, Blake 20032 (BRI). - Port Curtis Distr.;Lady Musgrave Island, Curtis L. 32 in Nov. 1966 (BRI).

138 R. C . STONE

Pandunus tectorius Parkins. var. heronensis (St John) Stone, comb. et stat. nova BASIONYM: P. heronensis St John PaciJic Science, 23: 89, f. 231 (1969). TYPE: as for basionym.

Phalanges obpyriform, 40-50 mm long, 26-32 mm wide, with very smooth rounded faces, apex truncate; carpels 5 -9, tips small, crowded : stigmas 2.0- 2.8 mm wide. SPECIMEN EXAMINED: Australia: Queensland; Heron Island, June 1960, R. F . Thorne 27225 (BRI), holotype.

In his description. St John compared this species to P. kaernbachii Warb., which is not at all closely related or similar; it belongs to the same subgenus but a different section, Pandanus section Fagerlindia Stone. Pandanus kaernbachii is limited to Melanesia, New Guinea, and the eastern Moluccas. P. tectorius var. heronensis differs very little from P. tectorius var. australianus; the smaller carpel tips, slightly more acute and prominulent stigmas, are the only apparent differences.

Pandunustector iusvar . stradbrookeenis (St John) B. C. Stone, comb. et stat. nova BASIONYM : P. stradbrookeensis St John, PaciJic Science, 23: 92, f. 289 ( 1969). TYPE : as for

Phalanges 60-65 mm long, 33-50 mm wide; broadly lance-ellipsoid, with very smooth, sometimes scarred but non-sulcate, faces; carpels mostly 9- 15, apices pyramidal or pyramidal-truncate; stigmas 2-4 mm long. SPECIMENS EXAMINED : Australia; Queensland; Currintin ( ?) Creek, 7 November 1929, White 6.509-A (BRI). - Hervey Bay, between Woodgate and Burrum R. mouth, 7 October 1929, White 6344 (BRI). - Wide Bay distr., near Bundaberg, sandy beach, 25 April 1936, Blake 22245 (BRI). - Moreton distr., Stradbrooke Island, Point Lookout, sandstone cliff, 31 May 1966, Blake 22733 (BRI). - New South Wales; Fingal Head, top ofsea cliff, 14 May 1967, Blake22789 (BRI; a form with somewhat depressed carpel tips). - Boganor Headland, 4 February 1961, H . W. CaulJield & W. G. Trapnell s.n. (BRI). The last-cited specimen bears an unpublished species name written by St John, alluding to the rather numerous carpels per phalange.

the basionym

Pandanus tectorius var. pedunculatus (R. Br.) Domin, Bibliotheca Botanica, 85: 25 1 ( 19 15). BASIONYM: P. pedunculatus R. Br., Prodromus: 341 (1810) TYPE: as for basionym.

Phalanges obpyriform, c. 76 x 47 mm, 39 mm thick, sides gently convex, smooth, but with shallow, narrow intercapellary sutures; or some sutures present only; carpel tips convex, the central apical sinuses 4-5 mm deep; stigmas 1-2 mm wide.

SPECIMENS EXAMINED : Australia : Queensland ; Wide Bay District, Fraser Island, Sandy Cape, on sand-cliffs above beach, 27 April 1966, Blake 22685 (BRI).

This collection, from the type locality of P. pedunculatus, matches the holotype (a single phalange) as well as could be reasonably expected; the condition of the phalanges, having been gathered from the ground where they had fallen, is such that the mesocarp and epicarp is rather weathered. There is variation in length, between 50 and 60mm, and this is less than in the type phalange, but the difference is not great. In discussions with Dr Blake (in 1971) it became apparent that he considered this collection and some others as probable members of P. pedunculatus.

PA.MDA.YUS IN AUSTRALIA 139

P a n d u n u s tectorius var.yorkensis (St John) B. C. Stone, comb. et stat. nova BASIONYM: P. yorkensis St John, PaciJic Science, 16: 344, f. 137 (1962). TYPE: as for

Phalanges 42-45 x 31-49 mm, cuneiform, with 10-1 7 (-25) divergent carpels, carpel tips rather blunt convex, separated by sinuses 6.5-8.0 mm deep, phalange sides smooth or with short, narrow lateral intercarpellary sutures; stigmas 2-3 mm long.

No further collections are reported here, but i t is of interest to note that the Australian collection illustrated by Martelli (1914, tav. 1, f. 3) as P. pedunculatus

basionym.

Figure I . Pundunus fecforiur in Green Island, showing the characteristic leaf attitudes - curving, drooping; the smooth bark; and maritime habitat.

10

140 B. C. STONE

R. Br. is very similar, although it shows much more acute carpel tips. This is also rather similar to P. tectorius var. novo-caledonicus Martelli, but differs in the higher number of carpels per phalange. Forms very similar have been observed by me in Micronesia as well.

According to St John (1962) the “closest relative” of his P. yorkensis is the Micronesian P. duriocarpus Martelli; which, also according to 9t John, is also the closest relative of P. oblatiapicalis, one of the species synonymized above; this being so, it follows that his P. yorkensis and P. oblatiapicalis would be closely related and similar, and they are. However, P. tectorius var. yorkensis has phalanges which are more different from those of P. tectorius var. pedunculatus than they are from those of P. oblatiapicalis.

VARIABILITY IN T H E POPULATIONS

Herbarium studies seldom permit an analysis of population structure. Fieldwork is particularly advisable for groups such as the pandans where the material that can be stuck to a herbarium sheet is often woefully inadequate to represent the indi\idual plant, let alone the species to which it is referred. The definition of a population is problematical, but it may be acceptable to consider that ‘all the

Figurr 2. Pandanus donuinemis, in Prince Regent River Reserve, Western Australia, representing Pandanus section Austrokeura, to show the characteristic leaf attitudes - rigid, erect. (Photograph courtesy of A. S. George, no. 12411.)

P.1 VD.1 tl'S IN .IVSI'R.IIdIAI 111

pandans on a small island' [night be taken as such. Green Island, off Cairns, Qiccnsland, is such ;i population. I t is clearly distinct, but composed of a moderate numher of indi\.idual pandms. .4 study of the synonymy listed a1xn.e shows that Green Island contains,

Figure 3. Pundunus solmsluubarhii, representing Pandanus section /lustrokeura, in Cairns, Queensland, to show the numerous vertical appressed aerial adventitious rootlets clothing the stem, a feature common in this section.

142 B. C. STONE

according to St John (1962, 1967), four species of Pandanus: P. adscendens, P. oblatiapicalis, P. sinuvadosus and P. viridinsularis. For each of these (in the protologj St John mentions another species which he calls the “closest relative” and these are :

P. adscendens - closest relative is : P. blakei. P. obliatiapicalis - closest relative is : P. duriocarpus Martelli. P. sinuvadosus - closest relative is : P. tectorius var. timorensis Martelli. P. viridinsularis - closest relative is : P. tectorius var. surigaensis Martelli.

Of these “closest relatives’’ it should be noted that one (P . blakei) is Australian; two others are varieties of P. tectorius, one from Timor, the other from Surigao (Philippines) ; and the last, P. duriocarpus, is a species of Palau in the West Caroline Islands, Micronesia. The closest relative of P. blakei is, according to St John, P. somersetensis St John, another Australian species; but in the protolog of

Figure 4. Pandanu rfolonifcr, representing Pandanu section Austrokeura, from Cairns, Queensland; two cephalia, to show the rugulose-costulate carpel faces of the phalanges giving a ‘mortise-end-tenon’ arrangement of the carpels, a characteristic of many species of this section.

P.4.VD.4.Yll.Y IN AUSTRALIA I43

P. somersetensis, no relative is mentioned. From a consideration of these relationships proposed by St John, it is apparent that he believed P. blukei to be closest to P. udscendens, while two others were compared directly with varieties of P. tectorius. Contrary to the suggestion of St John that P. blukei is close to P. somersetensis, the current understanding of the latter species is that it seems closest to P. oblutus St John and P. brookei Martelli, species which may be synonymous. These two species differ from P. lectorius and its nearest relatives in the possession of an elongate, pistillate cephalium ; in the larger stature of the plants, and in their occupation of a non-maritime habitat. Pundunus blukei conforms to most characters of P. lectorius (see Fig. I ) , including the subglobose to globose-suboblong cephalia (described as ellipsoid) ; the maritime habitat; the detailed form and size of the phalanges; carpel number; stigma size; endocarp position, and seed size. It is perhaps somewhat atypical in apparently having the extreme leaf apex with unarmed margins. In general it seems preferable to consider it as a synonym of P. tectorius. This would then bring P. udscendens into the pattern of relationship with P. tectorius.

Table 1. Some diagnostic differences between two sections in Pundunus

Character Pandanus strfinri Pandanu (P. fprfnrzus group)

Paridanus section . h f r n h r n

Leaf margin drntation Leaf apex normally serrate denticulate in both juvenile and adult plants

Leaf apex (of~en neirrly ;ill the marginl regularl~ but remotely denticulate in juveniles, sparsely armed or unarmed in adult p l m t s

Leaf attitude in life IXstal part drooping Leaf rigidly erect (unbroken leaves) (see Fig. I ) (See Fig. 2 ) Epidermal anatomy Stomata limited (nearly) to

abaxial surfacr of IraE; adaxial surface not zonate ~oi ia te

Stomata almost as numerous on adaxial a s an ahaxial ~ ~ r f a ~ e ; adaxial epidermis

Habit

Leaf wax distribution

Adventitious rootlets

Phalangelcarpels

Rarely or never with stolons Typically or oftrn with stolons; iidults tend to form colonies of identical (clon;ili individuals derived from these stolons

Leaf undersides markedly pale glaucous Leaf undersides vary from green to moderately glaucous

Lacking or rare

More or less smooth

Occasional to copious, often covering the stem (see Fig. : 3 )

Variable; smooth in P. spiralis and its relatives, but in other species, especially P. uhitez and P. s o h - l a u h u h z i and their closest relatives, the carpel faces are deeply interlocked by the mortise-and- tenon erect of the costulation (see Fig. 4) .

Carpel number/phalange Mostly less than 12, occasionally 15 or more (to c. 21 i

Oken subequal to apical mesocarp,Usually very short, often less than half (or but may exceed or be only half as even one-quarter) as long as the apical long mesorarp

Seldom less than 9, often I552 I , sometimes even more

Basal mesocarp length

Endocarp Usually submedian and occupying Usually massive and occupying more than about one-third of the phalange half of the phalange

144 B. C. STONE

a

w 2 cm

Figure 5. Phalange forms in Pandanus fecforius and related species. A, from holotype of P. blakei, after St John =P. tectorius. B, from holotype ofP. oblatiapicall, after St John, =P. fecforius. C, from holotype ofP. sinuuadow, after St John, =P. fectorius. D, from holotype of P . uiridinrularis, after St John, = P. tectorzus. E, from holotype ofP.yorkenris, after St John, = P. tectorzus var.yorkenris. F, from holotype ofP. adscendenr, after St John, = P. fecforius. G, from holotype ofP. pedunculafus, after St John, = P. fecforiusvar. pedunculatus. H, from holotype of P. brownii, after St John,=/'. tecforius. I, from holotype of P. heronemis, after St .John, = P . tectorius var. heronemis. J, from holotype of P. stradbrookeenris, after St John, = P. tcctorius uar.

PA.VD\‘DA.VCb’ IN AUSTRALIA 145

Only the question of P . duriocarpus remains. This Micronesian plant was based on an immature cephalium collected by Kanehira in Korror, Palau. This too may prove to be in the circle of affinities of P . tectorius, but the numerous forms of Pandanus in Palau have not yet been adequately studied. It seems somewhat unlikely that a species supposedly endemic to Green Island would be most intimately related to another supposed endemic in Palau, and I consider that the proposed relationship is deduced from a misleading similarity based on the atypical appearance of the immature phalanges of P . duriocarpus. In fact, in phalange details, P . adscendens conforms closely to P. blakei. The implication of these relationships is that a reticulate affinity of forms exists.

A field botanist in Green Island would find it difficult to accept that in the small confines and minor habitat variability of the island, four closely related species, indistinguishable in habit or in vegetative characters, and consisting presumably of only a few dozens of individuals, all with similar or identical pollination and fruit dispersal mechanisms, could all co-exist while maintaining genetic separation indefinitely. In 197 1, while collecting in Green Island, I looked in vain for any sign of habitat differentiation among the pandans there. In contrast it was not difficult to pick up phalanges fallen from various pistillate trees and realize that the forms named as the four endemic species were only a part of the variation in phalange shape which occurred, and that this variation was both greater than described and more continuous. Accordingly, P . adscendens, P . oblatiapicalis, P . sinuvadosus and P. viridinsularis are placed in synonymy with P. tectorius.

CHARACTER CONVERGENCE BEIWEEN SOME SPECIES OF P.4.VDA.VlrS SECTION fA.VDA.YlIS AND SECTION .4USTROKEUR.4 IN AUSTRALIA

There are several marked and apparently constant differences between Pandanus section Pandanus and Pandanus section Austrokeura (Figs 2-4 ) . In general, there is no difficulty in distinguishing them, as can be seen from Table 1. Nevertheless, there are a few indications that these sections may be connected. Such indications are found in certain taxa, or collections, which show either a mixed character or intermediate conditions. There are examples of the very short basal mesocarp of the ripe phalanges, rather typical of the species of Pandanus section Austrokeura, in a few species of Pandanus section Pandanus; the form called P . terrireginae (and here reduced to synonymy with P . tectorius) is an example. The high carpel number per phalange characteristic of the Austrokeura species is found in the form called P . brownii (although I suspect that this is merely a basal phalange: such phalanges found nearest the peduncular attachment are generally of a higher carpel number than the rest of the phalanges in the same cephalium). In Pandanus section Austrokeura the costulate (‘mortise-and-tenon’) appearance of the phalanges (Fig. 5 ) of most species such as P . whitei Martelli) is absent in P . spiralis R.Br. and its immediate relatives. Whether these examples indicate a current or prior gene flow between the sections Pandanus and Austrokeura is unclear, though the possibility

.Slradbrookeensis. K , one ofthecollections referred toRpedunculab by Martelli and illustrating hisconcept of this taxon [contrast with G, above). L, from the holotype of P. bowenemis, after St John,=P. tecforiur. M, from the holotype o f f . extraliltoralis, after St John, = P. techrius. N, from the holotype of P. hubbordii, after St John,=P. fectoriw. 0, from the holotype of P. feniregiac, after St John, =P. tectorius. P, P. durwcarpus Martelli, as reconstructed from a photograph in the protolog. Q o n e of the collections referred to P . pedunculalus by Martelli and illustrating his concept of this taxon (compare K above, and contrast with G, above).

146 B. C. STONE

exists and, for the time being, no better hypothesis of the origin of Pandanus section ilustrokeura has been proposed. The derivative nature of this section is suggested, in particular, by the reported tetraploidy of P . spiralis ( K . Jong, personal communication), the only known case of tetraploidy in the family. For most of the characters in Table 1 no intermediate states have been found.

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CHEAH. C. H. & STONE, B. C., 1975. Embryo sac and microsprangium development in Pandanus

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