Pollen morphology and taxonomy of the Phyllanthus species (Euphorbiaceae) native to new Caledonia

Review of Palaeobotany and Palynology, 53 (1988): 283 304 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

283

POLLEN MORPHOLOGY AND TAXONOMY OF THE PHYLLANTHUS SPECIES (EUPHORBIACEAE) NATIVE TO NEW CALEDONIA D. LOBREAU-CALLEN, W. P U N T and M. SCHMID C.N.RS., Laboratoire de Phandrogamie, and Laboratoire de Phytomorphologie de I'E.P.H.E., Musgum national Histoire naturelle, 16, rue Buffon, 75005 Paris (France) Laboratory of Palaeobotany and Palynology, State University Utrecht, Heidelberglaan 2, 3584 CS Utrecht (The Netherlands) Laboratoire de Phangrogamie, Musdum national Histoire naturelle, 16, rue Buffon, 75005 Paris (France) (Received November 11, 1986; revised and accepted M a r c h 23, 1987)

Abstract Lobreau-Callen, D., Punt, W. and Schmid, M., 1988. Pollen morphology and taxonomy of the PhyUanthus species (Euphorbiaceae) native to New Caledonia. Rev. Palaeobot. Palynol., 53:283 304. Forty-six species from New Caledonia have been examined; all belong to the subgenus Gomphidium, s.l., except two, one belonging to the subgenus Isocladus sect. Macraea, the other to the subgenus Kirganelia sect. Anisonema. The pollen of the species of the Gomphidium group resemble each other very closely and only three, undoubtedly related, pollen types have been recognized, viz. the P. acinacifolius, the P. loranthoides, and the P. aeneus types. Five evolutionary trends have been established and these have been used to explain the sequence of the primitive P. acinacifolius type to the P. aeneus type via the intermediate P. loranthoides type. Only small differential characters are found in the ornamentation, which ranges from finely reticulate, via coarsely reticulate to vermiculate, in the length of the colpi and in the outlines of the endoapertures which are usually exactly circular, but sometimes slightly lolongate. It was not possible to find parallel groups in the taxonomy of the species, representatives of the P. aeneus type being present in all the sections of the subgenus Gomphidium. There is a continuous v a r i a t i o n of pollen types, from less to more advanced. Descriptions of the previously described P. casticum and P. virgatus types have been extended.

Introduction

This study is part of a pollen morphological monograph on the genus Phyllanthus and is an addition to previous papers (Punt, 1967, 1972, 1980; Punt and Rentrop, 1974; Bor, 1979; Meewis and Punt, 1983). The main purpose is to find out if pollen morphology can help in unravelling the sectional relationships. By way of comparison, the pollen of other Phyllanthus species, especially those of species occurring in New Guinea, have been taken into consideration (Punt, 1980). A taxonomic revision of the genus for New Caledonia, undertaken by Schmid, will 0034-6667/88/$03.50

be published shortly. More than one hundred species are native to the area, almost all of them endemic. For taxonomic details the reader should consult the publications by Miiller (1866), Moore (1921), D~iniker (1932), Guillaumin (1928, 1948), Mangenot etal. (1977), Webster (1967), Webster and Airy Shaw (1971) and Schmid (1988). Material and methods

The majority of the specimens examined have been obtained from the Museum national d'Histoire naturelle (Phan~rogamie), Paris,

~ 1988 Elsevier Science Publishers B.V.

284 F r a n c e (P); a s m a l l p a r t f r o m t h e R i j k s h e r b a r i u m , L e i d e n , T h e N e t h e r l a n d s (L), a n d o n e from the Geobotanisches Institut of Ziirich, S w i t z e r l a n d (Z).

Specimens

examined

About one third of the specimens examined are representatives of new species, the descriptions of which have not yet been published. T h e s e s p e c i e s w i l l be d e s i g n a t e d b y t h e l e t t e r s A, B, C, etc. T h e s p e c i e s h a v e b e e n l i s t e d by s u b g e n e r a and sections, in accordance with the classificat i o n p r o p o s e d b y W e b s t e r . T h e s u b g e n u s Gomp h i d i u m is t a x o n o m i c a l l y a c h a l l e n g i n g g r o u p with poorly defined sections (Webster and Airy S h a w , 1971), a n d , a c c o r d i n g t o p o l l e n m o r p h o logical data, the placing of the different species o r s e c t i o n s m i g h t be s u b j e c t t o d i s c u s s i o n .

Subgenus Gomphidlum (Baillon) Webster, section Gomphidium P. bourgeoisii Baillon - - Baumann-Bodenheim et Guillaumin 7461 (P). P. castus S. Moore - - McKee 22843 (P). P. caudatus Mueller Arg. - - McKee 3678 (L), McKee 12253 (P). P. chamaecerasus Baillon. var. a--(Dendrophyllanthus ripicolus Guillaumin) McKee 3629 (L). var. b McKee 18080, 38369 (P). P. cornutus Baillon McKee 3973 (L). P. faguetii Baillon Balansa 1200 (L), McKee 27093 (P). P. jaubertii Vieillard ex Guillaumin - - Vieillard 2147 (P). P. koghiensis Guillaumin - - Schmid 5455 (P). P. platycalyx Mueller Arg. Balansa s.n. (L). P. poumensis Guillaumin - - McKee 20748 (P). P. pterocladus S. Moore McKee 13359 (P). Phyllanthus sp. A - - McKee 26002 (P). Phyllanthus sp. B Schmid 5439 (P). Phyllanthus sp. C McKee 31899 (P). Phyllanthus sp. D - - Schmid 5467 (P). Phyllanthus sp. E - - Veillon 2629 (P). Phyllanthus sp. F Schmid 5369 (P).

Subgenus Gomphidium section Adenogloehidion Mueller Arg. vel aft. (sections Eleutherogynium, Heteroglochidion, Polyandroglochidion included) Phyllanthus aeneus Baillon - - McKee 4159 (L), McKee 31916 (P). P. baladensis Baillon - - McKee 3185 (L), McKee 21313 (P).

P. baumannii Guillaumin - - Schmid 5171 (P). P. ligustrifolius S. Moore - - McKee 19634 (P). P. loranthoides Baillon - - McKee 19425 (P). P. montrouzieri Guillaumin - - McKee 20101 (P). P. ngoyensis Schlechter McKee 23909 (P). P. ouveanus D/iniker - - D~iniker 2117 (Z). P. peltatus Guillaumin - - Balansa 2355 (L); McKee 16626 (P). P. pronyensis Guillaumin - - Balansa 252 (P). P. salicifolius Baillon - - McKee 29015 (P). P. serpentinus S. Moore MacMillan 5064a (L); McKee 17486 (P). P. torrentium Mueller Arg. - - McKee 31892 (P). P. trichopodus Guillaumin - - McKee 26728 (P). Phyllanthus sp. G McKee 27016 (P). Phyllanthus sp. H. McKee 29446 (P). Phyllanthus sp. I Schmid 5385 (P). Phyllanthus sp. J Schmid 5408 (P). Phyllanthus sp. K Schmid 5396 (P). Phyllanthus sp. L - - Bamps 5925 (P). Phyllanthus sp. M McKee 13688 (P). Phyllanthus sp. N McKee 23763 (P). Phyllanthus sp. O - - Vieillard 3194 (P).

Subgenus Gomphidium (?), section Pentaglochidion Mueller Arg. P. kanalensis Baillon

Subgenus Isocladus (Wight) Baillon

McKee 34238 (P).

Webster,

section

Macraea

P. chrysanthus Baillon - - McKee 30410 (P). P. virgatus Forster f. - - McKee 4469 (P).

Subgenus Kirganella (Jussieu) Webster, section Anisonerna (Jussieu) Grisebach P. deplanchei Mueller Arg. - - McKee 40212 (P). M o s t o f t h e m a t e r i a l w a s i d e n t i f i e d by S c h m i d . A b o u t h a l f o f all t h e s p e c i e s k n o w n from the area have been studied. The pollen grains were prepared using the acetolysis m e t h o d as d e s c r i b e d by E r d t m a n (1952). Des c r i p t i o n s w e r e m a d e w i t h L e i t z a n d Zei ss l i g h t microscopes. The photomicrographs were taken with a Leitz Orthomat camera, using an i n t e r f e r e n c e g r e e n f i l t e r A1546. A c e t o l y z e d p o l l e n g r a i n s w e r e used for s c a n n i n g e l e c t r o n microscopy (SEM) and micrographs were t a k e n w i t h a J E O L J S M 35 C, i n t h e L a b o r a tory of Geology of the Paris Musbum national d ' H i s t o i r e n a t u r e l l e . T h e t e r m i n o l o g y u s e d is b a s e d m a i n l y o n R e i t s m a (1970) a n d E r d t m a n (1952). P a l y n o l o g i c a l t e r m s r e c o m m e n d e d by N i l s s o n a n d M f i l l e r (1978) a r e used.

285

Pollen types P o l l e n of the Phyllanthus species n a t i v e to New C a l e d o n i a are s e p a r a t e d into five pollen types: viz. the P. acinacifolius, P. aeneus, P. casticum, P. virgatus and P. loranthoides types. The first four are also f o u n d in species from New Guinea, and h a v e b e e n described in two previous papers (Bor, 1979; Punt, 1980). The descriptions h a v e been i m p r o v e d as new d a t a b e c a m e available, especially w i t h r e g a r d to the s t r u c t u r e of the exine and the measurements.

Key to the pollen types la. P o l l e n p a n t o c o l p o r a t e . . . . . . . . . . . P. virgatus type b. Pollen s y n c o l p a t e or z o n o c o l p o r a t e . . . . . . . . . . . . 2 2a. P o l l e n s p h e r o i d a l or s l i g h t l y p r o l a t e or o b l a t e spheroidal. Colpi d i s t i n c t l y a n a s t o m o s e d at t h e poles, s u n k e n at t h e e q u a t o r , n o t p a r t i c u l a r l y s u n k e n at t h e poles; d i s t i n c t l y r e t i c u l a t e or m i c r o r e t i c u l a t e ............................. P. casticum type b. P o l l e n s u b o b l a t e to oblate. Colpi n o t s u n k e n at t h e equator .................................. 3 3a. Colpi a n a s t o m o s e d at t h e poles, s l i g h t l y s u n k e n at t h e poles; o r n a m e n t a t i o n r u g u l a t e or i r r e g u l a r l y reticulate . . . . . . . . . . . . . . . . . . . . . . . . . . . P. aeneus type b. colpi n o t a n a s t o m o s e d at t h e poles, s o m e t i m e s s l i g h t l y s u n k e n at t h e poles; o r n a m e n t a t i o n r e t i c u l a t e or microreticulate ............................ 4 4a. M a r g i n s of t h e colpi f o r m e d by two d i s t i n c t p a r a l l e l m u r i , n o t or o n l y p a r t l y c o n n e c t e d w i t h t h e s u r r o u n d i n g o r n a m e n t a t i o n ; e n d s distinct, m o r e or less a c u t e .......................... P. loranthoides type b. M a r g i n s of p a r a l l e l m u r i a p a r t of t h e s u r r o u n d i n g r e t i c u l u m ; e n d s diffuse or a c u t e . P . a c i n a c i f o l i u s type

Description of the pollen types P. acinacifolius type (Plate I, 1, P l a t e II, 1-4) Pollen class: 3-zonocolporate. PIE ratio: S u b o b l a t e to oblate; r a r e l y oblate spheroidal. Apertures: E c t o a p e r t u r e - - colpus, v e r y narrow, slit-like, v a r y i n g in length, but n e v e r a n a s t o m o s e d at the poles or even n e a r l y so, not s u n k e n at the e q u a t o r , b u t s o m e w h a t s u n k e n t o w a r d s the poles; margins of parallel muri slightly u n d u l a t i n g , p a r t of the s u r r o u n d i n g reticulum; ends diffuse or acute; colpus mem-

b r a n e n o t visible; no costae. E n d o a p e r t u r e --porus, c i r c u l a r in outline; margins distinct; costae distinct, narrow. Exine: N e x i n e t h i n n e r t h a n sexine. Sexine 1 of distinct columellae, a b o u t as t h i c k as sexine 2. Sexine 2 a s e m i t e c t u m with r o u n d e d muri. Ornamentation: M i c r o r e t i c u l a t e or reticulate, v a r y i n g from fine to coarse. Muri thin, simplicolumellate, r o u n d edged. L u m i n a i r r e g u l a r in outline, usually all of a b o u t the same size, sometimes more or less elongate, with a c u t e angles, not d e c r e a s i n g t o w a r d s the colpi or the poles. In L - O analysis the c o l u m e l l a e c i r c u l a r to slightly elliptic in outline. Outlines: E q u a t o r i a l view - - elliptic, often s o m e w h a t e m a r g i n a t e at the a p o c o l p i u m sides ( s u n k e n colpi). P o l a r view - - c i r c u l a r to slightly t r i a n g u l a r , with the colpi in the angles. Measurements: P 12.5 22 pm; E 17 26 pm; P/E r a t i o 0.75-0.87 (rarely up to 0.91). Exine 1-2 pm. D i a m e t e r e n d o p o r i 3 6 pm. D i a m e t e r l u m i n a ca 1 pm up to 4 pm.

Species: P. bourgeoisii. Comment: P o l l e n of the P. acinacifolius type is m a i n l y c h a r a c t e r i z e d on its oblate shape and r e m a r k a b l e e c t o a p e r t u r e s which are v e r y narrow and b o r d e r e d by parallel, u n d u l a t i n g m a r g i n s which are parts of the r e t i c u l u m and slightly s u n k e n in the polar area. These f e a t u r e s are also c h a r a c t e r i s t i c of the P. aeneus type, but in this type the colpi are always a n a s t o m o s e d at the poles, w h e r e a s in the P. acinacifolius type the colpi are n e v e r syncolpate. The two types resemble each o t h e r very closely in o t h e r f e a t u r e s also, even in the r a n g e of variability. The r e t i c u l u m varies from fine to coarse and the l u m i n a are often elongate. In the P. acinacifolius type this e l o n g a t i o n is n e v e r e x t e n d e d into a v e r m i c u l a t e o r n a m e n t a tion. A n o t h e r difference is t h a t the c i r c u l a r e n d o a p e r t u r e is n e v e r l o l o n g a t e and always small in size. Pollen of the P. loranthoides type differs from the P. acinacifolius type only by the micror e t i c u l a t e o r n a m e n t a t i o n and the margins

286 o f t h e colpi w h i c h a r e n o t c o n n e c t e d o r o n l y partly with the surrounding ornamentation. P. l o r a n t h o i d e s t y p e ( P l a t e I, 2, 3; P l a t e II, 5-12) P o l l e n class: 3 - z o n o c o l p o r a t e . P / E ratio: S u b o b l a t e to o b l a t e ; r a r e l y o b l a t e spheroidal. Apertures: Ectoaperture colpus, narrow, slit-like, v a r y i n g in l e n g t h , b u t n e v e r a n a s t o m o s e d at t h e poles o r e v e n n e a r l y so; n o t s u n k e n at t h e e q u a t o r , b u t s l i g h t l y s u n k e n t o w a r d s t h e poles; m a r g i n s d i s t i n c t , t w o parMlel s o m e w h a t u n d u l a t i n g m u r i , n o t c o n n e c t e d or o n l y p a r t l y w i t h t h e s u r r o u n d i n g o r n a m e n t a t i o n , e i t h e r as t h i c k as t h e m u r i o f t h e r e t i c u l u m (P. l o r a n t h o i d e s ) o r s l i g h t l y t h i c k e r (Sp.A); ends d i s t i n c t , r o u n d e d o r a c u t e ; c o l p u s m e m b r a n e g r a n u l a r in S E M ; n o c o s t a e . Endoaperture p o r u s , u s u a l l y c i r c u l a r in outline, sometimes lolongate outline, margins d i s t i n c t ; size small; n a r r o w b u t d i s t i n c t c o s t a e .

E x i n e : N e x i n e t h i n n e r t h a n sexine. S e x i n e 1 o f d i s t i n c t c o l u m e l l a e , a b o u t as t h i c k as s e x i n e 2. Sexine 2 a semitectum with rounded muri. Ornamentation: Usually irregularly microretic u l a t e , s o m e t i m e s finely r e t i c u l a t e . M u r i thin, s i m p l i c o l u m e l l a t e , r o u n d edged, f u s e d at t h e top only, irregularly curved; lumina usually i r r e g u l a r in o u t l i n e , m o r e o r less e l o n g a t e . C o l u m e l l a e c i r c u l a r in o u t l i n e in L - O a n a l y s i s . O u t l i n e s : E q u a t o r i a l v i e w - - elliptic, o f t e n s l i g h t l y e m a r g i n a t e at t h e a p o c o l p i u m ( s u n k e n colpi). P o l a r v i e w - - c i r c u l a r to s l i g h t l y a n g u l a r , w i t h t h e colpi in t h e o b t u s e a n g l e s . M e a s u r e m e n t s : P. 12.5-15 pm; E 17-20 pm; P / E r a t i o 0.73-0.86. E x i n e 1 - 2 pm. D i a m e t e r endopori 3 6 # m . D i a m e t e r l u m i n a < l p m o r ca 1 p m wide. Species: P. l o r a n t h o i d e s , P. sp.A. T h e s p e c i e s m a y be s e p a r a t e d b y t h e following characters: P. l o r a n t h o i d e s : F i n e l y r e t i c u l a t e or m i c r o r e t i c u l a t e , l u m i n a a b o u t l p m in d i a m e t e r or

PLATE | (see p.287) (P. acinacifolius type, P. loranthoides type, P. aeneus type) 1. Phyllanthus bourgeoisii Baillon (Vink 15241, L) SEM; polar view, colpi not anastomosed at the poles, reticulum rather regular, margins of colpi connected with the surrounding ornamentation, x 2500. 2. Phyllanthus chamaecerasus Baillon (McKee 38369, P) SEM; equatorial view, parallel muri of colpi thicker than those of the reticulum, x 3000. 3. Phyllanthus loranthoides Baillon (McKee 19425, P) SEM; polar view, colpi not anastomosed at the poles, reticulum irregular, x 3000. 4. Phyllanthus sp. A. (McKee 26002, P) SEM; polar view and equatorial view, colpi not anastomosed at the poles, parallel muri slightly thicker than those of the reticulum, x 3000. 5. Phyllanthus faguetii Baillon (McKee 27093, P) SEM; polar view, parallel muri of the colpi thicker than those of the reticulum, x 3000. 6. Phyllanthus baumannii Guillaumin (Schmid 5171, P) SEM; polar view, parallel muri of the colpi not thicker than those of the reticulum, x 3000.

PLATE II (see p.288) ( x 2000) (P. acinacifolius type, P. loranthoides type) 1 4. Phyllanthus bourgeoisii Baillon (Baumann et al. 7461, P) 1, LM; polar view, circular outline. 2, LM; equatorial view, poles not sunken. 3, LM; ornamentation and colpus end. 4, LM; circular endoporus. 5 9. PhyUanthus loranthoides Baillon (McKee 19425, P) 5, LM; polar view, triangular outline. 6, LM; equatorial view, poles slightly sunken. 7, LM; ornamentation at high focus, lumina reticulum about 1 t~m. 8, LM; ornamentation at low focus. 9, LM; lolongate endoporus. 10 12. Phyllanthus sp. A (McKee 26002, P) 10, LM; ornamentation at high focus, lumina reticulum smaller 1 pm. 11, LM; ornamentation at low focus. 12, LM; circular endoporus.

287

PLATE I

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289 smaller. Muri of the colpus margins as broad and thick as those of the reticulum. P. sp.A: Mainly microreticulate, lumina usually <1 pm in diameter. Muri of the colpus margins broader and thicker t h a n those of the reticulum.

Comment: Pollen of the P. loranthoides type is mainly characterized by its oblate shape and ectoapertures, which are not very narrow, have undulating parallel colpus margins not connected or only partly with the surrounding ornamentation, and slightly sunken in the apocolpium area. These features are also characteristic of the P. aeneus type, but in the latter the colpi are always anastomosed or nearly so at the poles. In the P. loranthoides types the colpi are never syncolpate. On the other hand, the P. loranthoides type also resembles th at of the P. acinacifolius in a number of features. The main c h a r a c t e r is found in the colpi which are not anastomosed at the poles. In fact, the P. loranthoides type is intermediate between the P. acinacifolius and the P. aeneus types. In phylogenetic terms, this type is more advanced t han t hat of the P. acinacifolius and less advanced t han the P. aeneus type. An advanced c h a r a c t e r seems indicated if the margins of the colpi are loosened from the surrounding reticulum and also if the o r n a m e n t a t i o n is more complicated (rugulate, vermiculate). P. aeneus type (Plate I, 3, 5, 6; Plates III VI) Pollen class: 3-zonocolporate, r ar e l y 4-zonocolporate. Syncolpate. PIE ratio: Suboblate to oblate, r a r el y peroblate or slightly oblate spheroidal. Apertures: E c t o a p e r t u r e - - colpus, very long, usually anastomosed at the poles (syncolpate) or nearly so, often leaving a very small area in between the colpus ends, verry narrow, slitlike, not sunken at the equator, but usually slightly sunken towards the poles and at the poles; margins distinct, two parallel muri, not

connected or only partly with the surrounding ornamentation, these muri usually undulating; in some cases the inner margin bordering the colpus thicker and broader t han the outer one; ends, if present, diffuse, rounded; colpus membrane indistinct in LM, m i crogranul ar in SEM; no costae. E n d o a p e r t u r e - - porus, usually circular in outline, sometimes a little lolongate; margins distinct; costae distinct, narrow: Exine: Nexine usually t hi nner t han sexine, sometimes about as thick as sexine. Sexine 1 of distinct columellae as thick as sexine 2, sometimes a little thinner. Sexine 2 a semitecturn; muri rounded in cross-section, showing circular elements. Columellae of the muri margining the colpus usually a little higher and t hi cker in cross-section. Nexine often micro-endosculpturate in the intercolpia. Ornamentation: Usually irregularly reticulate, sometimes rugulate (vermiculate). Muri thin, simplicolumellate, fused at the top only, irregularly curved, often with loose ends. Lumina usually irregular in outline, often largely elongate. Columellae circular in outline in L - O analysis. Outlines: Equatorial view - - elliptic, usually slightly emarginate at the apocolpium, sides or at least truncate, short sides rounded in mesocolpium, but a little acute if a colpus coincides with the cross-section, thus giving the pollen grains a pear-shaped appearance. Polar view - - circular or angular, in which case, angles more or less acute with apertures in the angles; sides somewhat convex. Measurements: P 13.5-26 pm; E 17-34 ttm; P/E ratio 0.57-0.82 (rarely up to 0.90). Exine varying from l p m up to slightly more than 2 #m. Diameter endopori 2.5 6 #m. Species: Section Gomphidium: P. castus, P. caudatus, P. chamaecerasus, P. cornutus, P. faguetii, P. jaubertii, P. koghiensis, P. platycalyx, P. poumensis, P. pterocladus, and sp. B, C, D, E, F. Section Adenoglochidion (vel aft.): P. aeneus, P. baladensis, P. baumannii, P. ligustrifolius, P. montrouzieri, P. ngoyensis, P. ouveanus, P. peltatus, P. pronyensis, P. salicifolius,

290

P. serpentinus,

P. torrentium,

P. trichopodus,

a n d sp. G, H, I. J, K, L, M, N, O. S e c t i o n Pentaglochidion: P. kanalensis.

Comment: P o l l e n o f t h e P. aeneus t y p e c l o s e l y t h a t o f t h e P. acinacifolius a n d P. loranthoides t y p e s . I n p h y l o g e n e t i c t e r m s

resembles

t h i s t y p e is t h e m o s t a d v a n c e d . T h e c o l p i a r e longer than in the latter two types; the endoapertures are often lolongate which probably has to be considered as an advanced c h a r a c t e r a n d a l s o t h e o r n a m e n t a t i o n is m o r e complex. Pollen of the different species shows large variation, and this variation occurs with four m a i n c h a r a c t e r s o f i d e n t i f i c a t i o n : (1) o r n a m e n t a t i o n ; (2) o u t l i n e o f t h e e n d o a p e r t u r e s ; (3) c o l p u s e n d s ; (4) size. (1) O r n a m e n t a t i o n . T h e r e t i c u l u m c a n b e fine a n d m o r e o r l e s s r e g u l a r , b u t u s u a l l y i t is coarse and the lumina are irregular in outline, often elongate. In some species, the pollen

grains show an irregular pattern tending towards a rugulate (vermiculate) ornamentat i o n a n d i n a few c a s e s i t is d i s t i n c t l y vermiculate. Finely reticulate pollen grains a r e p r e s e n t o n l y i n a few t a x a (e.g., P. salicifolius). G o o d e x a m p l e s o f p o l l e n w i t h a c o a r s e r e t i c u l u m a r e P. aeneus, P. caudatus, P. peltatus, etc. T h e v e r y c o a r s e p a t t e r n i n p o l l e n o f P. b a u m a n n i i , P. kanalensis, a n d P. s p . N a r e transitions to the distinctly vermiculate pollen o f t h e s p e c i e s P. jaubertii, a n d P. s p . H . A s t h e o v e r l a p b e t w e e n a l l k i n d s o f o r n a m e n t a t i o n is great, no attempt has been made to use this character to differentiate species. (2) M o s t o f t h e s p e c i e s s h o w p o l l e n w i t h a circular endoporus. Some, however, possess a d i s t i n c t l y l o l o n g a t e o n e (e.g., P. chamaecerasus, P. faguetii, P. sp.M), b u t t h i s f e a t u r e a g a i n is n o t a l w a y s c l e a r l y v i s i b l e . A few t a x a h a v e p o l l e n i n w h i c h t h e e n d o a p e r t u r e is c i r c u l a r t o s l i g h t l y l o l o n g a t e (e.g., P. aeneus, P. kanalensis). (3) T h e m a j o r i t y o f t h e s p e c i e s h a v e p o l l e n

PLATE III (see p.291)

(P. aeneus type) 1, 2. Phyllanthus aeneus Baillon (McKee 31916, P)

3. 4. 5. 6,

l, SEM; polar view, colpi irregular in length, parallel muri of colpi not thicker than those of the reticulum, x 3000. 2, SEM; nexine sculpture (endosculpture), minutely sculptured around the endoporus, but more or less smooth in mesocolpium, x 3000, scale = 1 #m. Phyllanthus salicifolius Baillon (McKee 29015, P) SEM; fine reticulum, lumina < 1 #m, colpus grooves with small granules, × 10,000, scale = 1 #m. Phyllanthus sp. E (Veillon 2629, P) SEM; polar view, parallel muri distinctly thicker than those of the reticulum, × 3000. Phyllanthus faguetii Vieillard ex Guillaumin (McKee 27093, P) SEM; cross-section wall, smooth nexine in mesocolpial area, scale = 1 pm. 7. Phyllanthus jaubertii Vieillard ex Guillaumin (Vieillard 2147, P) SEM; distinctly microsculptured nexine, scale = 1 pm. SEM; microsculpture near the colpus absent, but present in the mesocolpial area (scale = 1 pm).

PLATE IV (see p.292) ( × 2000) (P. aeneus type)

1 4.

PhyUanthus aeneus Baillon (McKee 31916, P)

1, LM; polar view. 2, LM; equatorial view, poles sunken. 3, LM; ornamentation at low focus. 4, LM; circular endoporus. 5, 6, 7, 11. Phyllanthus kanalensis Baillon (McKee 34238, P) 5, LM; equatorial view, poles sunken. 6, LM; ornamentation at low focus. 7, LM; lolongate endoporus. 11, LM; polar view, triangular outline. 8 10, 12. Phyllanthus faguetii Vieillard ex Guillaumin (Vieillard 2147, P) 8, LM; equatorial view, sunken poles, 9, LM; lolongate endoporus. 10, LM; ornamentation at low focus. 12, LM; polar view.

291

PLATE III

L~

©

o~

CO

!

L

t~

293

TABLE I Palynological

data of

Species

Phyllanthus s p e c i e s p l a c e d i n t h e P. aeneus t y p e Syn.

fine Sect.

Endo.

E. d i a m . (#m)

lo lo

23 2'7 24 26

lo lo c lo c c.lo c c c c c c.sl.lo c c

27 23 19 28 29 22 22 20 24 22 22 22 23 18

+ + + vc + vc +

c.sl.lo c c c c.sl.lo c c c c c c c c.sl.lo c lo c c c c lo c c.sl.lo

22 25 21 29 25 28 29 34 21 24 26 30 c a 22 23 ~27 20-25 20 25 27 30 21 29 2 7 31 24 27 30-35 20 -25 18 22 23 27 21-23 28 30 24-29 17 20

vc

c.sl.lo

20-24

Reticulum coarse

verm.

Gomphidium

P. castus P. caudatus P. chamaecerasus var. a var. b

P. cornutus P. faguetii P. jaubertii P. koghiensis P. platycalyx P. poumensis P. pterocladus Phyllanthus sp. Phyllanthus sp. Phyllanthus sp. Phyllanthus sp. Phyllanthus sp.

B C D E F

syn. dif.

+ +

dif. syn-dif dif. syn syn. dif. syn. dif. dif. dif. dif. syn. syn. difo

vc vc + + + vc vc + + + + + + vc

dif. dif. syn. dif. dif-syn dif. dif. syn. syn. dif-syn dif-syn dif-syn syn. syn. syn. dif. dif-syn syn. dif. syn-dif dif. dif.

+ + vc vc + + + + +

ca ca

ca

30 27 22 31 33 25 27 24 27 24 25 24 27 21

S e c t . Adenoglochidion v e l aft.

P. aeneus P. baladensis (2) P. baumannii P. ligustrifolius P. montrouzieri P. ngoyensis P. ouveanus (2) P. peltatus P. pronyensis P. salicifolius (2) P. serpentinus P. torrentium P. trichopodus PhyUanthus sp. G Phyllanthus sp. H Phyllanthus sp. I (2) Phyllanthus sp. J (2) Phyllanthus sp. K PhyUanthus sp. L Phyllanthus sp. M Phyllanthus sp. N PhyUanthus sp. O Sect.

ca

+ + + vc vc

ca +

Pentaglochidion

P. kanalensis

dif-syn

s y n . = s y n c o l p a t e ; dif. = + a n a s t o m o s e d but not clearly syncolpate; endo. = endoaperture; c= circular; lo = l o l o n g a t e ; v c = v e r y c o a r s e ; c a = m o r e o r l e s s ; E. d i a m . = e q u a t o r i a l d i a m e t e r ; (2) = s p e c i e s b e l o n g i n g t o t h e s e c o n d s u b g r o u p o r c l o s e t o i t ( s e e i n fine).

294 grains in which the ectocolpi are not completely fused into a syncolpate structure (e.g., P. peltatus, P. sp.C). The ends of the colpi are, in fact, rounded and their closed ends touch each other or, sometimes even a small part of the reticulum is left between the colpi-ends (e.g., P. aeneus, P. chamaecerasus, P. sp.M). This feature is, however, difficult to see and is also not always consistent. (4) Finally, the size of the pollen grains also gives a mixed picture in the pollen grains. With some care it is, however, possible to divide them into three size groups: (I) Small-sized pollen. E diameter 17-20 gm, e.g., P. cornutus, P. sp.O. (II) a. Medium-sized pollen grains. E diameter 20 25 #m, e.g., P. baladensis, P. poumensis, P. salicifolius; b. Rather large-sized pollen. E diameter 25 28 ~m, e.g., P. baumannii, P. peltatus, P. pterocladus. (III) Large pollen. E diameter 29-35 gm, e.g., P. ligustrifolius, P. serpentinus, P. trichopodus, P. sp.H. In addition, it is possible to form two groups according to the features of the muri of the margins and the sculpture of the nexine. The first group shows the following features: (A) Near the equator the muri bordering the ectoaperture (innerside muri) are broader and thicker than those bordering the reticulum (outerside muri) (Plate I, 5). (B) Nexine smooth under the apertures, but microsculptured on both sides of them and again more or less smooth in the intercolpium (PlateIII, 7). Species of the section Gomphidium belong to this group. The second group shows the following differentiating features: Species of the section Adenoglochidion s.1. show similar parallel muri identical to those of the ornamentation (Plate I, 6) and the microsculpture of the nexine is present under the endoapertures and on both sides of them. The nexine is also smooth in the intercolpium (Plate III, 2). Pollen of P. kanalensis (section Pentaglochidion) shows the features of the second group but, in addition is microsculptured in the intercolpium.

P. virgatus type (Plate VII, 1, 2) A detailed description of the P. virgatus type is given in Punt (1980) but some additional information on the type is presented here. Apertures: Muri of the parallel margins not connected with the surrounding ornamentation, they widen out slightly above the endoaperture; colpus membrane microgranular, these microgranules arranged in two lines, parallel to the marginal muri. The endoporus circular with a distinct margin; costae narrow, smooth, distinct, in the middle of the ectocolpus. Exine: Nexine may be as thick as sexine, rather coarsely endosculptured near the apertures, but more finely under the areoles, and smooth under the apertures and the costae. Reticulum coarse, muri rounded and simplicolumellate; lumina irregular in outline, more or less angular and sometimes elongate. Outline: Usually ellipsoid, sometimes subspheroidal. Measurements (New Caledonian specimens): Longest axis 16-18 #m. Exine ca 2 gm. Diameter porus ca 1.5 #m. Diameter lumina 1 2 gm. Species: P. chrysanthus, P. virgatus.

Comment: The P. virgatus type is characterized by its hexagonal or pentagonal areoles and is very different from the pollen types in the subgenera Gomphidium and Kirganelia. The New Caledonian species of the subgenus Isocladus section Macraea have the same kind of pollen as those of New Guinea. In P. chrysanthus as well as in P. womersleyi (New Guinea) the number of areoles varies from 7 to 8 and the number of endopores is about 12. This pollen type with its apertural system probably follows the hypothetical line of successiformy as suggested by Van Campo (1976) and has to be considered an advanced pollen type. Both representatives, however, differ greatly from the Australian ones of the same subgenus like P. calycinus and P. hebecarpus. These latter species lack the syncolpate condition of the ectoapertures and undoubtedly belong to a more primi-

295 tive pollen type a n d a differrent t a x o n o m i c section. P. casticum type A detailed d e s c r i p t i o n of the P. casticum type is given in B o r (1979), P u n t (1980), a n d Meewis and P u n t (1983). Species: P. deplanchei (Plate VII, 3) N o t i n c l u d e d in the f o r m e r d e s c r i p t i o n of the type is the f e a t u r e t h a t the m u r i of the m a r g i n s widen out slightly a b o v e the e n d o a p e r t u r e s . M e a s u r e m e n t s (of P. deplanchei): P 13.5-17 pm, E 1 3 - 1 7 p m , P/E r a t i o 0.79-1.17. Exine: 1.5-2 ttm. D i a m e t e r e n d o p o r u s ca 1.5/~m. Comment: The P. casticum type differs from the P. aeneus type by its distinctly a n a s t o m o s e d colpi w h i c h are more or less s u n k e n in the equatorial area, its r e t i c u l u m with more or less a n g u l a r l u m i n a and sphaeroidal P/E ratio. The type is c h a r a c t e r i s t i c for most of the species belonging to the subgenus Kirganelia section Anisonema, with representatives in New G u i n e a and Africa (Punt, 1980; Meewis and Punt, 1983).

Evolutionary trends The genus P h y U a n t h u s is represented in New Caledonia by a b o u t 105 native species belonging to three subgenera: viz., the s u b g e n e r a Gomphidium, Isocladus, and Kirganelia. G o m p h i d i u m is by far the most diversified subgenus, with a b o u t 100 w o o d y species of w h i c h all, with one or two exceptions, are endemic. Its pollen is r e l a t i v e l y h o m o g e n e o u s . Only t h r e e pollen types could be established and these are v e r y similar. The pollen characters c a n be a r r a n g e d as proposed by P u n t (1967), and several e v o l u t i o n a r y trends m a y be suggested. In respect to the m o r p h o l o g y of the apertures, t h e r e are t h r e e i m p o r t a n t trends: (1) P o l l e n 3-colporate -~ s y n c o l p a t e . T r e n d 2A (Punt, 1967). (2) M a r g i n s of colpi n o t divided into two parallel margins, p a r t of the s u r r o u n d i n g r e t i c u l u m -* distinct parallel m a r g i n s n o t c o n n e c t e d or only p a r t l y with the s u r r o u n d i n g o r n a m e n t a t i o n . T r e n d 4 (Punt, 1967).

PLATE V (see p.296) (P. aeneus type) 1. Phyllanthus montrouzieri Guillaumin (McKee 20101, P) SEM; polar view, parallel muri of the colpi not thicker than muri of the reticulum, x 3000, scale = 10 zm. 2. Phyllanthus serpentinus Moore (McKee 17486, P) SEM; polar view, parallel muri of the colpi not thicker than those of the reticulum, x 3000. 3, 4. PhyUanthus torrentium Mueller Arg. (McKee 31892, P) 3, SEM; nexine around endoporus smooth, scale = 1 pm. 4, SEM; equatorial view, parallel muri of the colpi not thicker than those of reticulum, x 3000, scale = 10 #m. 5. Phyllanthus jaubertii Vieillard ex Guillaumin (Vieillard 2147, P) SEM; polar view, parallel muri of the colpi distinctly thicker than those of the reticulum, x 3000. 6. Phyllanthus kanalensis Baillon (McKee 34238, P) SEM; polar view, parallel muri of the colpi not thicker than those of reticulum, x 3000, scale = 10 #m, PLATE VI (see p.297) ( × 2000) (P. aeneus type) 1 4. Phyllanthus jaubertii Vieillard ex Guillaumin (Vieillard 2147, P) 1, LM; polar view, outline triangular. 2, LM; ornamentation at low focus. 3, LM; ornamentation at high focus. 4, LM; circular endoporus. 5 7. Phyllanthus trichopodus Guillaumin (McKee 26728, P) 5, LM; lolongate endoporus. 6, LM; polar view, triangular outline. 7, LM; equatorial view, poles distinctly sunken. 8, 9. Phyllanthus caudatus Mueller Arg. (McKee 12253) 8, LM; ornamentation at low focus. 9, LM; lolongate endoporus.

296

PLATE V

(for e x p l a n a t i o n see p.295)

297

PLATE VI

|

ii~iiii~ii~,,~i ¸¸~i~,, ~~, ~' ~ ~'~%~i,ii !iiiii~~

'i

~ii~illii~

ii!ii~o

!~!~i!~!!i~!~

~!i!¸¸

~

~,~iii!!I

g (for explanation see p.295)

298 P L A T E VII

(P. virgatus type, P. casticum type) 1, 2. Phyllanthus chrysanthus Baillon (McKee 30410, P)

3.

1, SEM; ornamentation of the nexine, more or less smooth around the endoapertures and granulate in the interporium, x 10,000, scale = 1/~m. 2, SEM; quadrigonal areole, parallel lines of micro-granules between colpus and margins of the reticulum, × 1000, scale = 1/xm. Phyllanthus deplanchei Mueller Arg. (McKee 40212, P) SEM; equatorial view, × 1000, scale = 1/~m.

(3) A p e r t u r a l m e m b r a n e s m o o t h --~ abundantly and coarsely granular. In r e s p e c t to the shape: (4) P o l l e n ca s p h e r o i d a l --* oblate or peroblate. T r e n d 1 (Punt, 1967). In r e s p e c t to the o r n a m e n t a t i o n : (5) R e t i c u l u m r e g u l a r , l u m i n a more or less a n g u l a r --~ i r r e g u l a r l y e l o n g a t e --* more or less r u g u l a t e (vermiculate). T r e n d 7 (Punt, 1967). T h r e e sections are r e c o g n i z e d in the s u b g e n u s (Schmid, 1988): viz., Gomphidium s.str. (including the section Physoglochidion), Adenoglochidion s.1. ( i n c l u d i n g the sections

Eleutherogynium, Heteroglochidion, Polyandroglochidion), and Pentaglochidion. In the section Gomphidium, the most primitive P. acinacifolius type, the m o s t a d v a n c e d P. aeneus type a n d the i n t e r m e d i a t e P. loranthoides types are present. In this section a c o n t i n u o u s s u c c e s s i o n of pollen types exists. In the section Adenoglochidion, only two pollen types are present: viz. the P. loranthoides and P. aeneus types. The series is t h u s i n c o m p l e t e and the s e c t i o n c a n s c a r c e l y be d i s t i n g u i s h e d from the p r e v i o u s section by pollen m o r p h o l o g y . Nevertheless, a few distin-

299

guishing pollen characters occur. In the section Gomphidium, the two parallel muri of the colpus margins are different, whereas in the section Adenoglochidion these muri are identical at the equator and similar to those of the ornamentation. Besides this, another character distinguishes the section Adenoglochidion from Gomphidium: this is the sculpture of the nexine. In the section Adenoglochidion, the whole endoaperture is bordered by a distinct, fine micro(endo)sculpture; in the section Gomphidium, the endoaperture is encircled by a smooth scabrate ring (P. sp.C, P. sp.F) or by a scabrate nexine (P. faguetii). The nexine is distinctly microsculpturate on both sides of the endoapertures. In both sections the nexine is smooth in the intercolpium. Pollen of the section Pentaglochidion is very similar to that of the P. aeneus type of the section Adenoglochidion, but its nexine ornamentation differs in having a micro(endo) sculpture under the aperture as well as in the intercolpium. Species with the lowest evolutionary level grow on schistosandstoneous soils and have a relatively wide geographical distribution in New Caledonia as well as in New Guinea. On the other hand, the greater part of the pollen types with an intermediate or derived evolutionary level are present in species associated with ultrabasic soils of fairly recent geological history (Late Eocene, Miocene). The colonization of these special soils and the geographically insular isolation of the first Gomphidium species might explain the extraordinary diversity of the subgenus in which the speciation has resulted in such an overwhelming number of different flower types and large number of pollen types. The section Gomphidium also occurs outside New Caledonia, but with a smaller number of species, mainly in New Guinea. Their pollen was studied by Punt (1980) and all belong to the P. acinacifolius type, which is a pollen type of a low evolutionary level. The subgenus Gomphidium also includes the section Nymania, a section not present in New Caledonia, but well represented in the sur-

rounding areas, mainly New Guinea. According to the observations of Punt (1980), most species have a P. aeneus pollen type with fairly advanced characters. They show a distinctly vermiculate reticulum with high columellae and more or less anastomosed lumina (muri with loose ends). Moreover, the inner muri of the margins are thicker and broader than those of the outer ones and of the reticulum. This character relates pollen of the section Nymania to t h a t of the section Gomphidium, but the structure of the exine, particularly of the reticulum is certainly more advanced. There is one New Guinean species in the section Nymania with more primitive pollen in the P. acinacifolius type (P. flaviflorus). It is a pity that a species with pollen intermediate between the P. acinacifolius and P. aeneus types was not found in this section. The evolutionary trends of pollen of the species of the section Gomphidium from New Caledonia and New Guinea are represented diagramatically in Fig.1. The pollen types in this figure have been established by at least one distinct differentiating character (evolutionary trend) or by a combination of differentiating characters. By applying evolutionary trends, as given above, the pollen types can be arranged in a sequence from primitive to advanced. Primitive types are placed at the base of the scheme and the most advanced ones can be found at the top. The scheme of relationships gives a clear division of the subgenus into two groups based on the geographical distribution. The classification of the types shows a continuous series of pollen types in New Caledonia. The section Nymania with species having the most advanced pollen of the subgenus Gomphidium occurs mainly in New Guinea, but also has representatives in Australia and the Solomon Islands. They might have been derived from more primitive pollen in the section Gomphi-

dium. The long isolation ( 8 0 m . y . B . P . ) of New Caledonia might explain the distinct speciation and continuous evolution from primitive to advanced pollen types. New Guinea is not as

300

z=

I

cO I-

..... ~ / Sect. OMPHIDIUM ADENOGLOCHIDION S e c t . PENTAGLOCHIDION~

i

~C~')

~ / P AENEUS . pu]lentype lb la 3a-b

I~

a;4;5a) la

1a

i

Sect. GOMPHIDIUM / Sect. ADENOGLOCHIDION

il

LORANTHOIDES pollen type

Z ~'~

~ ~Se

~.

NYMANIA

P. A C I N A C I F O L

(./

US

pollen type

O

, 3b O

(1;2;3;4;5)

/N4- 4

O

(1;2;4;5)

Sect. GOMPHIDIUIM

ct.

Z

I

Fig.1. Scheme of relationships within the subgenus Gomphidium derived from pollen morphology and geographical distribution. (The numbers figuring on the diagram correspond to the numbers given in the list of evolutionary trends, Table II). ~ probable filiation -*-*-*possible, but not probable filiation.

old (40 m . y . B . P . ) as New Caledonia. It was, moreover, for some time (20-15m.y. B.P.) linked to the Indomalesian continents. The competition between the species may explain the missing of an intermediate pollen type and the great diversification of the subgenus Gomphidium at an advanced level.

The subgenus Kirganelia, well diversified in Africa (Meewis and Punt, 1983), has only a single native species in New Caledonia (P. deplanchei). It has pollen of the P. casticum type. This type is not very advanced in comparison to the African ones. The subgenus Isocladus is represented in

301 TABLE Ill The evolutionary trends in the s u b g e n u s 1. Ectocolpi long 2. Ectocolpi ectoccdpi syncolpate.

Gomphidium

nearly syncolpate

2. ectocolpi not s u n k e n at equator --* ectocolpi s u n k e n at equator. 3. colpi with muri appearing more or less as a part of the s u r r o u n d i n g r e t i c u l u m 2. colpi with two similar parallel muri and the outer, m a r g i n a l m u r u s not connected or rarely partly connected with the surr o u n d i n g o r n a m e n t a t i o n £ colpi with two parallel muri, the inner one broader and thicker at the equatorial area t h a n the outer one, which is not connected or only partly connected with the surrounding o r n a m e n t a t i o n (reticulate or vermiculate pattern). 4. Pollen grains reticulate -~ vermiculate. 5. L u m i n a closed, a n g u l a r --* l u m i n a open, elongated (muri with loose ends).

New Caledonia by two species, one endemic (P. chrysanthus) and one widespread weed (P. virgatus). Both species have the same pollen type which is relatively advanced. P. womersleyi from New Guinea has the same pollen type (Punt, 1980). Representatives in Australia, however, are more diversified and show some primitive colporate pollen grains.

Taxonomy The monograph by Miiller (1866) is still a basic work for the study of the New Caledonian Phyllanthus species. The discovery of many new species and the more careful study of those already described has shown that several of Mfiller's sections, mostly endemic ones, cannot be maintained. Due to lack of knowledge of the genus on a regional scale, however, it does not seem timely to propose a new system of classification for the about 105 native species of New Caledonia and those of the surrounding territories (Australia, New Guinea and the Melanesian archipelagoes). There is no doubt that the division into subgenera as proposed by Webster (1956), mainly based on palynological and plant architectural data, gives a framework within which i t is tempting to place the

different groups of taxa recognized. According to this classification, nearly all New Caledonian species of Phyllanthus have to be included in the subgenus Gomphidium. The remaining four species belong either to the subgenus Isocladus, section Macraea, with one endemic species and another one widely distributed throughout the Pacific, or to the subgenus Kirganelia, section Anisonema, with also one endemic species and another one represented in Melanesia. Morphological studies have, however, led to the conclusion that one has to be cautious in accepting this first attempt at regrouping. Indeed, the majority of the New Caledonian species have very similar pollen, and the insular conditions combined with a greatly contrasting environment within a limited space might have favoured the differentiation of many taxa. These taxa probably originated from a single taxon. It appears that all these species (more than a hundred) all belong to the subgenus Gomphidium and they can be clearly differentiated into two groups differing by floral morphology and some vegetative characters. The first group, with about 45 species, corresponding to the section Gomphidium Baillon, has for a long time been considered to be restricted to New Caledonia. It is, however, represented outside this island by a number of taxa. Several species have been found in New Guinea, among which P. bourgeoisii, also present in New Caledonia. The group is well characterized by the male flower with a perianth composed of two circles of three tepals which alternate regularly, are slightly imbricate in the bud and the inner circle of which is petal-like. The androecium consists of three m u c r o n a t e stamens standing close to each other, with free generally very short filaments (P. pterocladus excepted) and longitudinal anthers. The disc is composed of three separate glands. The inflorescences are generally unisexual with the female flowers isolated and standing separate from the male ones. With regard to the vegetative characters, it is noticeable t hat most of the species have fairly open branching, that many species are more or less pubescent and t hat leaves are often

302 opposite. More th an four fifths of the species are found only on ultrabasic soils and this leads to the conclusion t h a t the group with these advanced characters has probably originated late in time. Its affinities with representatives of the section Nymania, comprising at least 25 species in New Guinea, but not present in New Caledonia, are patent. It is obvious t hat both sections belong to the same subgenus. With regard to the palynology of the group, it is noticeable th a t three pollen types occur (P. acinacifolius type, P. loranthoides type, P. aeneus type) ranging from relatively primitive to distinctly advanced. In New Caledonia, the most primitive pollen type (P. acinacifolius type) is represented by only one species, whereas in New Guinea all species of the section Gomphidium show this primitive pollen type. On the other hand, all but one of the species of the section Nymania occurring in New Guinea, have pollen of the P. aeneus type, whereas the intermediate pollen type (P. loranthoides type) is not observed. It is of interest t h a t the two New Caledonian species showing the most primitive pollen (P. bourgeoisii and P. sp.A) are r a t h e r isolated in taxonomic view. All o th er species of the group show pollen of the advanced P. aeneus type. P.pterocladus, also having pollen of the P. aeneus type, is very special in its floral morphology and might be placed in a separate section. As discussed above, the pollen grains of the different species vary from each other more or less distinctly, e.g. in length of the colpi (more or less clearly syncolpate, or only diffusely), ornamentation, outline of endoaperture, etc. Therefore, it is not possible to separate the species of the section Gomphidium from those of the section Nymania on the basis of distinct palynological data. Probably the evolution of the characters has followed parallel ways in the two areas. Pollen of the species occurring in the section Nymania are as a whole more advanced and there may exist a discontinuity, but it is too early to put too much emphasis on these results. M611er (1866) distinguished two sections in

the species mentioned here under the section Gomphidium which he called Gomphidium and Physoglochidion. The latter is characterized by the accrescence of the tepals of the inner circle completely covering the fruit when mature. However, in the same group of species all intermediate stages from small tepals to accrescent, very large ones, are found. To the group Physoglochidion there belong, among others, P. faguetii, P. jaubertii, P. koghiensis, and P. platycalyx. It is obvious from Table I t hat these species cannot be separated from those in the Gomphidium group on the basis of palynological data. The second group comprises about 60 species and can be distinguished from the section Gomphidium mainly on the morphology of the male flower. The perianth is normally composed of five r a t h e r similar tepals which are widely imbricate. Two types of androecium exist: (a) In the first subgroup, the number of stamens varies from 2 to 20, but is generally five. The filaments are very short, sparsely inserted on a r a t h e r wide receptaculum. The more or less developed disc is continuous or irregularly split (Adenoglochidion, Heteroglochidion, Polyandroglochidion); (b) The second subgroup has three or five stamens and the filaments are more or less elongate, diverging from the center of the receptaculum. The anthers are short, longitudinal or transverse. The disc is generally reduced, ring-like or absent (Eleutherogynium emend.). In the second group as a whole the inflorescences are generally bisexual, often comprising several female flowers. The plants are not pubescent and only a few taxa (4 5 species) have opposite leaves. On the other hand, in many species the foliate branchlets are narrowly grouped at the end of the stem. The group is well represented on ultrabasic soils, but about 25 species, most of them of the second subgroup b, are only found on sandstones which are usually older than the ultrabasic outcrops. In taxonomic view, subgroup (a) is probably r a t h e r primitive and in any case less advanced t han the section Gomphidium. It is probably

303

e n d e m i c to N e w C a l e d o n i a . T h e s u b g r o u p (b) seems m o r e a d v a n c e d a n d is r e p r e s e n t e d outside the t e r r i t o r y by at l e a s t one species in V a n u a t u ( E a s t of Fiji Islands, ca 165°W, 15°S). T h e species P. kanalensis, for w h i c h Mfiller (1866) c r e a t e d t h e s e c t i o n Pentaglochidion, is c h a r a c t e r i z e d by a n a n d r o e c i u m c o m p o s e d of five s t a m e n s , w i t h p a r t l y c o n n a t e filaments, and a n o v a r y w i t h five loculi w h i c h is a n e x c e p t i o n in Phyllanthus species ( u s u a l l y t h r e e loculi). I t is r e l a t e d to the second group, b u t also h a s affinities w i t h species of t h e s u b g e n u s Kirganelia. Its pollen definitely b e l o n g s to the P. aeneus type. W i t h p a l y n o l o g i c a l d a t a on the n e x i n e it w o u l d be possible to m a k e a d i s t i n c t i o n bet w e e n the first g r o u p (section Nymania included) a n d t h e second. T h e s e d i f f e r e n t i a l c h a r a c t e r s of the n e x i n e are, h o w e v e r , difficult to observe. T h e second g r o u p gives rise to a special p r o b l e m w i t h r e g a r d to the pollen c h a r a c t e r s . The m o s t a d v a n c e d pollen a r e f o u n d in species w i t h a p r i m i t i v e floral m o r p h o l o g y , w h e r e a s the less a d v a n c e d P. acinacifolius pollen t y p e is n o t r e p r e s e n t e d . T h e i n t e r m e d i a t e P. loranthoides t y p e is r e p r e s e n t e d by one species of the second s u b g r o u p (b) a n d the m o s t a d v a n c e d pollen in t h e P. aeneus t y p e (pollen s y n c o l p a t e , w i t h a g r e a t d i a m e t e r , v e r m i c u l a t e ornam e n t a t i o n a n d a n e n d o a p e r t u r e w h i c h is often l o l o n g a t e ) is o n l y f o u n d in t h e first s u b g r o u p (a) (e.g., P. trichopodus, P. sp. H.). F r o m t h e s e results, one m a y c o n c l u d e t h a t no p a r a l l e l i s m exists b e t w e e n t h e e v o l u t i o n of pollen a n d floral m o r p h o l o g y . T h i s e m p h a s i z e s the f a c t t h a t p l a n t s r e p r e s e n t a m o s a i c of c h a r a c t e r s w h i c h m a y evolve i n d e p e n d e n t l y of e a c h o t h e r at v e r y different speeds. T h e r e f o r e , it m a y be s u g g e s t e d t h a t Phyllanthus pollen g r a i n s of the N e w C a l e d o n i a n species h a v e e v o l v e d m o r e q u i c k l y in g e o l o g i c a l t i m e t h a n the flowers. T h e y m i g h t h a v e c h a n g e d in a m a n n e r p a r a l l e l w i t h s o m e o t h e r c h a r a c t e r s of the flowers, b u t at the t i m e at wh~ ~u t h e pollen w a s m o r e or less stabilized t h e m o r p h o l o g y of t h e flowers m i g h t c o n t i n u e to evolve d u r i n g a v e r y long perind of g e o l o g i c a l t i m e while p r e s e r v i n g

the e v o l u t i v e levels of the pollen grains. B e a r in mind, h o w e v e r , t h a t the e v o l u t i o n m i g h t h a v e t a k e n p l a c e the o t h e r w a y a r o u n d . F o r this r e a s o n , it is n e c e s s a r y to u n d e r t a k e m o r e c o m p a r a t i v e studies of o t h e r f e a t u r e s of the p l a n t s to solve the a p p a r e n t c o n t r a d i c t i o n s b e t w e e n pollen a n d t a x o n o m y t h a t exist at present.

Acknowledgements T h e a u t h o r s a r e g r a t e f u l to P r o f e s s o r Dr. P. M o r a t , D i r e c t o r of the L a b o r a t o i r e de P h a n ~ r o g a m i e (P) for b e i n g so k i n d as to supply the m a t e r i a l n e c e s s a r y for the p a l y n o l o g i c a l studies. T h e y are i n d e b t e d to M. C h a l o p i n (M.N.H.N.) for p r e p a r i n g the pollen slides, to Y. Cazal (C.N.R.S.) for p r i n t i n g the microg r a p h s a n d to Y. Vidal (C.N.R.S.) for t y p i n g the text. T h e y wish to express t h e i r sincere t h a n k s to Dr. G.C.S. C l a r k e for c o r r e c t i n g the E n g l i s h t e x t a n d for his c r i t i c a l c o m m e n t s on the manuscript.

References Bor, J., 1979. Pollen morphology and the bi-reticulate exine of the Phyllanthus species (Euphorbiaceae) from Mauritius and R~union. Rev. Palaeobot. Palynol., 27:149 172. D~iniker, A.U., 1932. Ergebnisse dem Reisen von Dr. A.U. D~iniker nach Neu-Caledonien und der Loyalty Inseln. Katalog der Pteridophyta und Embryophyta siphonoganum. Beibl. Vierteljahrsschr. Naturforsch. Ges. Z/irich., 19: 210--235. Erdtman, G., 1952. Pollen Morphology and Plant Taxonomy, Angiosperms. Almqvist and Wiksell, Stockholm, 539 pp. Guillaumin, A., 1928, Euphorbiac~es de la Nouvelle Cal~donie. Arch. Bot. II. M~m., 3:1 25. Guillaumin, A., 1948. Flore de la Nouvelle-Cal~donie. Phan6rogames. O.R.S.C., Paris, 369 pp. Mangenot, G., Bancilhon, L. and Mangenot, S., 1977. Caryologie du genre Phyllanthus (Euphorbiaceae, Phyllanthoideae). Ann. Sci. Nat. Bot. Paris, 12e S~r., 18: 71 126. Meewis, B. and Punt, W., 1983. Pollen morphology and taxonomy of the subgenus Kirganelia (Juss.) Webster (genus Phyllanthus, Euphorbiaceae) from Africa. Rev. Palaeobot. Palynol. 39: 131-160. Moore, S., 1921. A systematic account of the plants collected in New Caledonia and the Isles of Pines by Prof. R.H. Compton in 1914. Euphorbiaceae. J. Linn. Soc. Bot., 45: 393-409.

304 Miiller, J., 1886. Phyllanthus in Decandolle, Prodr. 15(2): 274 436. Nilsson, S. and Muller, J., 1978. Recommended palynological terms and definitions. Grana, 17: 55-58. Punt, W., 1967. Pollen morphology of the genus Phyllanthus (Euphorbiaceae). Rev. Palaeobot. Palynol., 3: 141-150. Punt, W., 1972. Pollen morphology and taxonomy of section Ceramanthus Baillon s.1. of the genus Phyllanthus (Euphorbiaceae). Rev. Palaeobot. Palynol., 9: 175 202. Punt, W., 1980. Pollen morphology of the Phyllanthus species (Euphorbiaceae) occurring in New Guinea. Rev. Palaeobot. Palynol., 31:155 177. Punt, W. and Rentrop, J., 1974. Pollen morphology of the Phyllanthus species occurring in the continental United States. Rev. Palaeobot. Palynol., 16:243 261.

Reitsma, Tj., 1970. Suggestions towards unification of descriptive terminology of angiosperm pollen grains. Rev. Palaeobot. Palynol., 16:39 -60. Schmid, M., 1988. Euphorbiac6es: Phyllanthus. Flore de la Nouvelle-Cal6donie, vol. 14, in press. Van Campo, M., 1976. P a t t e r n of pollenmorphological variation within taxa. Linn. Soc. Symposium, 1:125 137. Webster, G.L., 1956. A monographic studies of the WestIndian species of Phyllanthus. J. Arnold Arbor. Harv. Univ., 37:340 357. Webster, G.L., 1967. The genera of Euphorbiaceae in the South-eastern United States. J. Arnold Arbor. Harv. Univ., 48:303 430. Webster, G.L. and Airy Shaw, H.K., 1971. A provisional synopsis of the New Guinea taxa of Phyllanthus (Euphorbiaceae). Kew Bull.,, 26:85 109.