L(otunicatJournul oJihe Linnean . h e & ( 1 9951, 117 135-1 45. With 10 figures

Cytotaxonomic observations in tropical Vaccinieae (Ericaceae)

RUTH ATKINSON*, KWITON JONG** AND GEORGE ARGENT

Royal Botanic Garden Edinburgh, Inuerleith Row, Edinburgh, EH3 5LR

Received April 1994, acceptedjir publication February I995

Chromosome numbers are reported for 36 accessions representing 31 species from nine genera of the tribe Vaccinieae, family Ericaceae. The plants are tropical and come from Southeast Asia and Central and South America. The taxonomy of the tribe is outlined in these regions. Genera are often poorly defined and taxa were chosen to reflect the range of variation of the Vaccinieae. Most Southeast Asian Vaccinium species were diploid (2n = 24) as were those of Agapetes subgenus Agapetes (apart from the Himalayan A. Java), Agapetes scortechinii and Costera endertiz. All other accessions were found to be polyploid. The correlation between polyploidy, geographical distribution and the possession of an ‘anatomical complex’ of the leaf and stem in Vaccinieae of New Guinea and the neotropics is discussed.

ADDITIONAL KEY WORDS:-Agapetes - anatomy - cytology - Dimorphanthera - neotropics Sphyrospemum -- Southeast Asia - Vaccinium.

CONTENTS Introduction . . . . . . . . . . . . . Previous cytological studies of the Vaccinieae . . , . . ,

Material and methods . . . . . . . . . . . Results . . . . . . . . . . . . . . Discussion . . . . . . . . . . . . . .

Chromosome morphology and basic number . . . . . Sphyrospemum, Macleania and & t e a . . . . . . Vaccinzum and $rnpIyia . . . . . . . . . .

Dimorphanlheru . . . . . . . . . . . . Cavenduhia and Sagria . . . . . . . . . . AgapeteJ . . . . . . . . . . . . . Costera . , . . , . . , . , , , ,

Geographical distribution of polyploids in the tropical Vaccinieae Conclusions . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . References . . . . . . . . . . . . . .

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INTRODUC‘rION

The Vaccinieae D. Don as treated by Stevens (1971) is a large widespread tribe of woody plants in the Ericaceae Juss. ranging in stature from low sub- shrubs to small trees. They are distributed globally and are most characteristic of boreal regions and tropical mountains, and it is in the tropics where diversity

*Present address: The Herbarium, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB. **Also at: Department of Plant and Soil Science, University of Aberdeen, Old Aberdeen, Aberdeen AB9

2UD, Scotland.

0024-4074/95/020135+11 $08.00/0 135

0 1995 The Linnean Society of London

136 R. AIKINSON ETAL.

is highest. They are often an important constituent of the vegetation in the habitats in which they are found.

In the tropics they occur at a range of altitudes with the largest number of species centred at moderate altitudes, often at the cloud level in mountainous areas. In Southeast Asia they are found up to 4000 metres on Mt. Kinabalu in Borneo and the Main Range of New Guinea. They are frequently epiphytic but some species dominate the vegetation as small trees, for example Vuccinium miguelii Boerl. on Sumatran volcanoes and V. dominuns Sleumer in New Guinea (Sleumer, 1967). In the neotropics the greatest diversity of the Vaccinieae is centred at the northern end of the Andes (Smith, 1932), but they occur throughout the Americas.

Stevens (1971) reviewed the classification of the Ericaceae and on the basis of anatomy and morphology he concluded that the Vaccinieae is a heterogeneous assemblage, particularly in the New World. The taxonomic boundaries of many genera close to Vuccinium L. are poorly defined and the same applies to generic subsections. In Southeast Asia where the greatest diversity of Vaccinium occurs (c. 260 species in six sections, Sleumer, 1967) the New World situation is paralleled by Agupetes D. Don, which is distinguished quite arbitrarily from Vuccinium on corolla shape and size. Even a relatively well-defined genus such as Dimorphuntheru F. Muell. has been the subject of uncertainty. Sleumer in Flora Malesiana (1 967) included section Puchyunthu Sleumer within Vuccinium on the basis of its short flowers. This section was moved by Stevens (1974) into Dimorphuntheru on account of corolla structure, stamen and vegetative morphology.

There are fewer species of Vaccinium in the neotropics but they represent the small-flowered remnants left over after numerous large-flowered vaccinioid genera have been defined. On morphological grounds they do not appear to be particularly closely related. The delimitation of the tribe Thibaudieae Hook. f., which contained many of the neotropical genera, caused confusion and Sphyrospmum Poepp. & Endl. was shunted between the Thibaudieae and the Vaccinieae (see Smith, 1932, 1933). Stevens recognized no consistent differences and transferred the genera from the Thibaudieae into the Vaccinieae. At a lower taxonomic level distinctions between neotropical genera can be difficult to find. Vacinium section Oreades Sleumer is as different from the rest of the genus as is the West Indian genus ~ o ~ ~ n n ~ Vahl (now known as @mp&siu C. Presl.).

On the basis of leaf and stem anatomy Stevens (1972) recognized two subgenera in the genus Agupetes. The old genus Puphiu Seem. is morphologically very similar to continental Asian Agapetes and Stevens included it in that genus at subgeneric rank. Puphiu has a complex of anatomical characters, which are rare in the Asian Vaccinieae and that sets it apart from the rest of Agupetes. These characters are deep-seated phellogen in the stem, a prominent, often lignified hypodermis, a more or less extensively lignified spongy mesophyll, expanded vein endings and a petiole bundle which usually forms a closed cylinder of tissue. This 'anatomical complex' is found in many of the neotropical Vaccinieae, whereas in Southeast Asia it is restricted to Dimorphantheru, Costeru J. J. Sm. and some members of Vuccinium section Oariunthe Schltr. (although the latter have a superficial phellogen).

Consideration of the taxonomic background outlined above suggested key taxa for cytological investigation with the main objective of providing additional information on relationships in the tropical Vaccinieae.

CYTOI'AXONOMY OF TROPICAL VACCINIEAE 137

PREVIOUS CYTOLOGICAL STUDIES OF 'THE VACCINIEAE

Little work has been done on the cytology of tropical Vaccinieae. Chromosomes in the Ericaceae are small, more or less uniform in gross morphology, do not stain well and the material is difficult to squash (Hall & Galleta, 1971). Table 1 gives published counts for tropical Vaccinieae summarized with the results of the present study in Table 2. Cuuendishiu Lindl. has had only one count published (Hunziker, Xifreda & Wulff, 1985), there are two for Dimorphanthem (MacDougall & Vander Kloet, 1982), two for Agupetes (Larsen, 1966; Callan, 1941) and one for Diogenesiu Sleumer (Argent & Brunton, 1984). One count each has also been made for Symphysiu and Gonocuhx Planch & Linden (Nevling, 1969). Only 13 counts are recorded from about 350 taxa of tropical Vuccinium (MacDougall & Vander Kloet, 1982; Argent & Brunton, 1984; Larsen, 1966). Apart from the count for Cuuendishiu (n = c. 26) and Symphysiu (2n = c. 38), all have x = 12 and diploids, triploids and tetraploids are reported.

Some Vuccinium species are important fruit crops in North America and studies have been carried out on commercial species. Hall & Galleta (197 1) studied chromosome morphology in Vuccinium, section C$unococcus A. Gray of the commercial blueberries and work has been concentrated on this group (e.g. Darrow et ul., 1944). One of the North American blueberries, Vuccinium

TABLE 1. Previously published chromosome counts in tropical Vaccinieae

Taxon

Chr. count (refs in brackets, Ploidy

see Table 2) level Origin

Vaccinium section Oarianthe

I? cyclopense J. J. Sm. V. myrsinoides Schltr.

V. acrobracteatum K. Schum. V. horizontale Sleumer V. auricul@lium Sleumer V. recticulato-uaosum Sleumer V. schodda' Sleumer V. uaringiaefolium (Blume) Miq. V. bracteatum Thunb.

I.: reticulatum J. J. Sm.

V. poasanum Donn. Sm. V. sprengeliz (G. Don.) Sleumer

D. amplectens (Sleumer) Sleumer

A. serpens (Wight) Sleumer A . saxicola Craib

G. portoncenszl (Urb.) A. C. Sm.

S. racemosa (Vahl) Stearn synonym = V. padahpensis Sw.

C. pubescens (Kunth) Hemsl.

section Bracteata

section Macropelma

section Oreades

Lhogenesia Sleumer

Agapetes

Gonocabx Planch & Linden

Symphysia C. Presl.

Cavendishia

271 = 24(1) 2x Papua New Guinea 2n = 24(1) 2x Papua New Guinea

2n = 24(1) 2x Papua New Guinea 2n = 24(1) 2x Papua New Guinea

n = 12(2) 2x Papua New Guinea n = 12(2) 2x Papua New Guinea n = 12(2) 2x Papua New Guinea n = 12(2) 2x Indonesia, Java n = 24(3) 4x Thailand

2n = 24(1) 2x Hawaii

n = 24(2) 4x Honduras 2x Thailand n = 12(3)

n = 24(2) 4x Ecuador

2n = 24(4) 2x ? 2x Thailand n = 12(3)

n = 23/24(5) 4x Puerto Rico

2n = c. 38(5) 3x/6x Puerto Rico

2n = 36(1) 3x/6x Martinique

n = c. 26(6) 4x Colombia

138 R. ATKINSON ET A L

TABLE 2. Summary of existing and new chromosome counts for tropical Vaccinieae

Ploidy level New counts (published Existing counts

2n counts in brackets) (refs in brackets)

Agapetes subgenus Agapetes Agapetes subgenus Paphia section Pseudqapeks:

Agapetes scortechinii Cauendishia Costera Dimorphanthera Disterigma Diogenesia Gonocahx $mphysia Macleania Sagria Sfilyrospenum

Vaccinium Asia Neotropics

24, 48 7 2

24 48 24 72

z 80

96 48 48, c.48, 96, c. 96. c. 130

24, 48 48

2x, 4x(2x) 6x

2x 4x (4x)

6x (4x) 8x? rw (44 (3x or 6x1 8x 4x

4x, 8x, I Ix?

2x, 4x(2x) 4x (4x)

n = 12 (3), 2n = 24 (4)

n = c. 26(6)

2n = 48 (1)

2n = 24(2)

2n = c. 38(5), 2n = 36(1) n = 23/24(5)

2n = 24 (3, 1) 2n = 48 (2)

Refs for Tables 1 and 2: 1, MacDougall & Vander Kloet (1982); Argent & Brunton (1984); 3, Larsen (1966); 4, Callan (1941); 5, Nevling (1969); 6, Hunziker, Xifreda & Wullf (1985).

colymbosum L., has populations of different levels of polyploidy (up to 6x) which demonstrates that variation can be expected within a single species (Vander Kloet, 1988).

MATERIAL AND METHODS

The Royal Botanic Garden, Edinburgh has a comprehensive collection of tropical Ericaceae with particularly good representation of Southeast Asian material. There is also a wide range of neotropical species from many genera. Counts from this collection have previously been made for Aguuriu (DC.) Hook. f., Diogenesiu, Guultheriu L. and I’accinium (Argent & Brunton, 1984).

Chromosomes were observed in root squashes of vegetatively propagated material. Of the two chemicals used for pretreatment, 1 -bromonaphthalene for 2 h at room temperature ( 6 . 20°C) produced more reliable results than paradichlorobenzene. Each was prepared as a saturated aqueous solution.

After pre-treatment the roots were washed and placed in freshly made Farmer’s solution (3 : 1 ethanol : glacial acetic acid) and stored in this solution at 4°C. Hydrolysis in 5N HC1 at 20°C for 50 min proceeded staining in Feulgen prepared according to Fox (1969). The roots were left in the Feulgen for 1 to 2 h and then placed in tap water for up to 10 min to intensify the stain. Roots were extremely hard and additional maceration in a 1 : 1 mixture of 4% cellulase and 4% pectinase for 30 min at room temperature after staining was essential to soften them sufficiently to obtain good squashes.

The chromosomes stained only faintly with Feulgen and needed counterstaining with 0.9% aceto-orcein before squashing under a coverslip. The use of phase contrast microscopy was essential and greatly enhanced visibility of the

CYTOTAXONOMY OF TROPICAL VACCINIEAE 139

chromosomes. All the photomicrographs were taken on 35 mm Kodak Technical Pan film. Drawings were traced from suitable photographic prints.

Voucher herbarium specimens are lodged at Royal Botanic Garden, Edinburgh.

RESULTS

See Figures 1-9 for photographs and drawings of chromosomes observed. All the counts listed in Table 3 are first reports apart from those of V. acrobracteatum and V. poasanum. That of V. poasanum is a re-count of the accession previously counted by Argent & Brunton (1984). The counts for D i s t m p a , Macleania, Sap-ia, Sphyrospermum and Costera are the first for these genera. They show wide variation in chromosome number from 2n = 24 to 2n = c. 130, the latter in one accession of Sphyrospermum cordfolium and one of S. majus, indicating the occurrence of very high levels of polyploidy in tropical Vaccinieae.

DISCUSSION

Chromosome morphology and basic number

The Vaccinieae is very uniform in chromosome morphology (see Figs 1-9). Consistent characters of the Vaccinium karyotype found in this study are; small size (1.3-2.9 pm), a satellite on at least one chromosome and median centromeres. All these characters are found in other Vaccinieae and the chromosomes become smaller as their number increases. The karyogram that Hall & Galleta (1971) produced for North American Vaccinium was very similar to observations made in this study. As already mentioned, satellites were visible in a number of accessions. Agapetes j a u a has four satellited chromosomes (three of which can be seen in Fig. 3), supporting the hypothesis that it is tetraploid.

The Ericaceae has a basic number of x = 12 (Raven, 1975) although dysploidy does occur in the family. For example x = 11 is found in Gaultheria (Middleton & Wilcock, 1990) and x = .13 in Rhododendron L. (Janaki Ammal, Enoch & Bridgwater, 1950). The basic number is generally conservative within tribes and variation indicates a major divergence. All the genera studied here have x = 12, but there is great variation in ploidy levels.

Figures 1-4. Photographs of mitotic metaphases. Fig. 1 , Dimorphantheru megacalyx 2n = 72. Fig. 2, Costera endertii 271 = 24. Fig. 3, Agapetes Java 2n = 48. Fig. 4, Vaccinium lobbii 2n = 24. Arrows indicate chromosomes with satellites. All at the same scale.

140 R. ATKINSON ET-AL.

5

Figures 5-9. Drawings of mitotic metaphases. Fig. 5, Macleania rupestis 2n = 96. Fig. 6, Sphyrospennum cordqolium (RBGE no. 196506767) 2n = 96. Fig. 7, Vaccinium coriaceum 2n = 24 (arrow indicates the position of a satellite). Fig. 8, Dzmorphanthera eleganantissima 2n = 7 2 . Fig. 9, CauendGhaa JtrobiliJka 2n = 48.

Sphyrospermum, Macleania and Disteriprna

Macleania ntpestris and S~hyrospermum cord~lium both have 2n = 96, indicating that they are octoploids. S. cordijjlium has different levels of polyploidy, with tetraploid (2n = 48), octoploid and a higher level indicated by 2n = c. 130 which is also found in S. mius. These counts suggest that the chromosome number could be derived from 11 times x = 12. Further work is needed to clarify this.

There appears to be some correlation between chromosome number and morphological variation in Sphyrospermum cord$olium. The three accessions of S. cordijdium of 2n = c. 48 and 2n = 48 are all from Ecuador and the count of 2n = 96 is from a morphologicaly distinct plant from Costa Rica.

S. buxijjlium also has 2n = c. 96, showing that octoploids are found in other species of Sphyrospermum. Disterigma alaternoides could not be counted with certainty,

CYTOTAXONOMY OF TROPICAL VACCINIEAE 141

TABLE 3. Chromosome numbers of all accessions studied

Taxon 2n* RBGE

no. Provenance

Agapetes D. Don subgenus Agapetes

A. Java (Hook f.) Sleumer A. incuruata (Griff.) Sleumer

var. major Airy Shaw

subgenus Paphia (Seem.) Stevens section Paphia (Seem.) Stevens

A. meiniana F. Muell. A. stenantha (Schltr.) Sleumer

section Pseudagapetes Airy Shaw A . scortechinii (King & Gamble) Sleumer

Cavmdishia Lindl. C. strobilijira (Kunth) Hoerold C. tarapotana Benth. & Hook. f.

C. endertii J. J. Sm. Costera J. J. Sm.

Dimorphanthera F. Muell. section Dzmoiphanthera Sleumer

D. elegantissima K. Schum. section Pachyantha (Sleumer) Stevens

D. amplifilia (F. Muell.) Stevens var. oblonga (Sleumer) P. Woods

D. amplfolia (F. Muell.) Stevens var. &antea (Sleumer) P. Woods

section ‘Trochilanthe Schltr. D. kapteriana Schltr.

D. megacahx Sleumer Dirterigma Nied.

D. alatemoides Nied. Macleania Hook.

M. rupestns (Kunth) A. C. Sm Sagris Klotzsch

S. warszcwiczii Klotzsch Sphyrospmum Poepp. & Endl.

S. bux$iolium Poepp. & Endl. S. cordfolium Benth.

S. majus Griseb.

Vaccinium L. section Bracteata Nakai

I! acrobracteatum K. Schum. K bancanum Miq. I! bracteatun Thunb. I! coriaceum Hook. f.

I! loranthijilium Ridl. section Dirtaigmopsis Sleumer

I! consanguineum Klotzsch

48 (4x)

24 (2x)

72 (6x) 72 (6x)

24 (2x)

48 (4x) 48 (4x)

24 (2x)

72 (6x1

72 (6x)

72 (6)

72 (6x)

72 (6x)

> 80 (8x1’)

96 (8x)

48 (4x)

c. 130 ( I Ix?) c. 48 (4x) c. 48 (4x)

48 (4x) 96 (8x)

c. 96 (8x) c. 130(1 Ix?)

24 (2x) 24 (2x) 24 (2x) 24 (2x)

24 (2x)

48 (4x)

19861405

19791238

19792585 1 96823 15

19680672

19762376 19762343

19801 343

19730420

19682561

19630477

19681744

19761270

19762397

1976235 1

19761009

19762390 19762358 19762387 19762354 19650676 1973 1303 19732047

19681354 19773327 19300201 19772535

19680663

19772948

&hillin& Nepal

St Andrew Acc. 1246/67W Assam, India.

Queensland, Australia Woods 2842, Papua New Guinea

Woods 61 3, Peninsular Malaysia

Argent 430, Ecuador Argent 422, Ecuador

Argent, N. Borneo

Stevm, Papua New Guinea

Woods 3205, Papua New Guinea

Woods 209, Papua New Guinea

Woods 2101, Papua New Guinea LB24, Papua New Guinea

Argent 527, Ecuador

Argent 525, Ecuador

Herklots, Costa Rica

Argent, Ecuador Argent, Ecuador H526, Ecuador Argent 52 I@), Eruador Lankester, Costa &a No provenance information Prance 2003 I , Brazil- Venezuela border.

Woods, Papua New Guinea Kerb, Sarawak No provenance information Gardener MG152, Mt Kinabalu, Sabah Woods, Papua New Guinea

Costa Rica

142 R. ATKINSON ET AL

TARLE 3. cont.

Taxon RBGE

2n* no. Provenance

section Galeope!alum 0. J. Sm.) Sleumer I.: pseudodia&etalum Ng 24 (2x) 19793398 Stone 14388, Malaysia

V. dens$olium J. J. Sm. 48 (4x) 19761290 Argent, Papua New Guinea V. jnisterrae Schlt. 24 (2x) 19761354 Argent G3, Papua New Guinea

V. poasanum Donn. Sm. 48 (4x) 19730609 Herklots 116, Honduras

V. borneense W. W. Sm. var. poianum (J. J. Sm.) Sleumer 24(2x) 19820809 Sinclair B Argent 110, Sarawak

V. lanceiiolium (Ridl.) Sleumer 24 (2x) 19820748 Szncluzr B Argent 162, Sarawak I.: lohhii (Ridl.) Sleumer 24 (2x) 19820853 Sznclazr & Argent 154, Sarawak

section Oarianthe Schltr.

section Oreades Sleumer

section Rzgiolepis (Hook. f.) J. J. Sm.

* Ploidy levels are indicated in brackets.

but a number of 2n = >80 indicates that it too is a high polyploid in common with some Sphyrospermum.

Vaccinium and Sjmphysia

The majority of Vaccinium species counted (ten out of 13) were diploid, but the remaining three were tetraploid with 2n = 48. V. densfolium (2n = 48) is found in New Guinea and placed in section Oarianthe by Sleumer (1967). Section Oarianthe has been identified as divergent from other Southeast Asian sections of Vaccinium. Not only does it have a highly reduced inflorescence but some members of the section share the ‘anatomical complex’ with Agapetes subgenus Paphia, Dimorphanthera, Costera and neotropical Vaccinieae (Stevens, 1971). The other member of Oarianthe studied, V. jinisterrae, has 2n = 24, making this section the only one of Southeast Asian Vaccinium studied for which two ploidy levels are known. The two neotropical Vaccinium both have 2n = 48 and further counts would be useful to ascertain the extent of polyploidy in New World Vaccinium.

Two previously published chromosome numbers for Sjmphysia racemosa (Vahl) Stearn of 2n = c. 38 (Nevling, 1969) and 2n = 36 (MacDougall & Vander Kloet, 1982), from different localities (see Table l), suggest that this taxon is triploid which could indicate the presence of apomixis. Alternatively, it could be hexaploid with x = 6.

Dimorphanthera

All six species from three sections of Dimorphanthera counted in this study are hexaploid, although MacDougall & Vander Kloet (1 982) reported tetraploids (2n = 48) in D. anchonfua J. J. Sm. and D. denticulzjira Sleumer which are in the same section, Trochilanthe, as the hexaploids, D. elegantissima and D. megacahx. Thus two ploidy levels occur in this section.

The members of section Pachyantha share the same chromosome number as those from sections Dzmorphanthera and Trochilanthe, supporting the move of this

CYTOTAXONOMY OF TROPICAL VACCINIEAE 143

section from Vaccinium (Stevens, 1974). Dimorphanthera is restricted to New Guinea and it is notable that species counted here share the same number as Agapetes stenantha from New Guinea and A. meiniana from northern Australia.

Cavendishia and S a p i a

Our results demonstrate that the two species of Cavendishia counted share a common chromosome number with the tetraploid neotropical species of Vaccinium and Subria. Cavendishia pubescens Hemsl. was reported by Hunziker et al. (1985) as 2n = c. 52 but no illustrations were given for this species. In the light of counts of 2n = 48 for C. tarapotana and C. strobil@ra and the prevalence of x = 12 as a basic number in the Vaccinieae, a recount would be worthwhile.

Agapetes

Agapetes shows the greatest generic variation in chromosome number in this study, with three records of diploids, one tetraploid and two hexaploids. The genus is clearly separated into two subgenera (see Introduction). The variation in chromosome number reported here correlates with geographical distribution and with the possession of the ‘anatomical complex’ but there are notable exceptions. Two members of the New Guinea and Australian subgenus Paphia are hexaploid whilst the third member counted of this subgenus, A. scortechinii is diploid. This species occupies an intermediate position in Agapetes in terms of morphology and geography; it is found in Peninsular Malaysia (see Fig. 10 for distribution of accessions), but it belongs to subgenus Paphia because of its anatomical complex. A correlation between the possession of an anatomical complex and polyploidy in the Vaccinieae is strongly indicated by several taxa

Figure 10. Distribution of newly counted diploid and polyploid Vaccinieae in Asia and Central America (inset). KEY. Asia: V 4x Agapetes Jlaua; 2x Agapetes subgenus Agapetes, Agapetes scortechinii, Costera endertii, Vaccinium sections Bracteata, Galeopetalum, Rigiolepis; 0 2x, 4x Vaccinium section Oarianthe; + 6x Dimorphanthera, Agapetes subgenus Paphia. Neotropics: 4x Vaccinium poasanum, V. consanpinem, Sagria wanzcwic~ii, Sphyrospemzum cordijilium, Cauendishia; 0 8x Sphyrospennum cordijlium & S. buxgolium (c. 8x & >8x), Macleania mpestris, Diskrigma sp. (8x?).

144 R. ATKINSON ETAL.

in this study, but A. scortechinii seems to be anomalous in being diploid. This suggests that it is closer to continental Agapetes (subgenus Agapetes) than may be deduced from its anatomy. Not all species of subgenus Agapetes counted are diploid, Agapetes Java (2n = 48) is tetraploid, showing that differences in chromosome number can be found in this group.

Costera

Costera endertii has a chromosome number of 2n = 2 4 and is a member of a genus identified by Stevens (1972) as belonging to the Pacific and New World Vaccinieae on account of their possession of the anatomical complex. The count for this species therefore indicates that the relationship between the possession of deep seated phellogen, etc. and polyploidy is complicated. The accession of Costera endertii counted was diploid, in common with Agapetes scortechinii, and both possess the anatomical complex. Costera is a poorly understood genus and more work needs to be done to clarify the extent of variation in anatomical and cytological characters.

Geographical distribution of po&doids in the tropical Vaccinieae

Polyploidy in the Vaccinieae is strongly associated with geographical distribution (Fig. 10). Stevens (1974) commented on the close morphological affinities of Dimo~hanthera with Sa&a as an example of a tropical amphitranspacific affinity. In this study the distribution of polyploidy indicates that this affinity may be found widely in the tropical Vaccinieae. Diploids have been found only in western Malesia and mainland Asia (except for V. Jinistemae) whilst the polyploids are found almost exclusively in New Guinea, Australia and the neotropics (except for Agapetes j a u a in Nepal).

CONCLUSIONS

It is possible that many tropical Vaccinieae in both the Malesian and the New World tropics belong to basically polyploid genera and many of these show the anatomical complex outlined in the Introduction. Other taxa (Agapetes subgenus Agapetes and the majority of Southeast Asian Vaccinium) lack this combination of anatomical characters and although polyploidy is found in this group it is likely to have an origin independent of that of the first group.

The existence of diploid taxa in groups that are believed to have the anatomical complex (Costera and Agapetes section Pseudugapetes) is problematic. More counts in several of the genera, particularly neotropical Vaccinium, Sphyrospermum, Disteripa and in Southeast Asia, Costera, would be useful in determining the extent of variation in polyploidy and the relationship with anatomical characters. Incomplete as the results presented above are, they still suggest that current generic limits in the Vaccinieae do not mesh well with the developing genealogy of the group.

CYIOTAXONOMY OF TROPICAL VACCINIEAE 145

ACKNOWLEDGEMENTS

This study was started as a thesis by the first author for completion of an M.Sc. in the Biodiversity and Taxonomy of Plants (run jointly by Royal Botanic Garden Edinburgh and University of Edinburgh). Completion of the work was supported by financial assistance from RBGE and is gratefully acknowledged. The investigation was made possible by the RBGE's extensive living collection and thanks are extended to the horticultural staff who maintain it. Thanks are also due to Peter Stevens (Harvard University Herbaria) for his helpful comments and encouragement. James Luteyn from New York Botanical Garden provided assistance with identification and Jim Ratter of RBGE commented on the manuscript.

REFERENCES

Argent GCG, Brunton D. 1984. Some chromosome numbers in Ericaceae. Notes Royal Botanzc Garden, Edinburgh 41: 561-564.

Callan HG. 1941. The cytology of GaulthetQa wisleyensis (Marchant) Rehder, a new mode of species formation. Annals of Botany 5: 579-585.

Darrow GM, Camp WH, Fischer HE, Dermen H. 1944. Chromosome numbers in Vaccinium and related groups. Bulletin Tory Botanical Club 71: 498-506.

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64: 1-53.

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