TROPICS Vol. 7 (Il2):93-103 Issued Oct., 1997

The Dlverse Occupant Fauna tn Eptphyttc -plants, Hgdttoplngfirm m.wleganum (Rublaceae) ln New Gulnea

Tomohiro MAEYAMA, Osamu KITADE & Tadao Marsuvroro Department of Biology, Graduate School ofArts & Sciences, The University ofTokyo,3-8-1 Komaba, Meguro, Tokyo 153, Japan

ABSTRACT There are many ecological studies of occupying the myrmecophytes in relation to the interactions between hosts and symbionts. However, the other occupants of myrmecophytes have been scarcely studied. It is very important to investigate all the occupants and arboreal fauna to clarify their symbiotic relationships. We surveyed the complete occupant fauna inhabiting the epiphytic myrmecophytes, Hydnophytum moseleyanum in mangrove forests in Papua New Guinea. A diverse fauna was revealed, that was composed of 11 ant species and 39 species of other groups. Almost all the occupant species would be commensals facultatively utilizing the space inside the myrmecophytes for their inhabitation. The existence of the epiphytic myrmecophytes should play a significant role for the maintenance of arboreal because myrmecophytes provide the shelters and moisture for arboreal and markedly increase potential sites for their dwelling.

Key Words: ant-plant / occupant / symbiosis / plant-animal interaction / biodiversity / New Guinea

Special attention has been focused upon the interactions between ants and myrmecophytes (ant-plants) in many studies in the tropics and subtropics, one of the most interesting phenomena of plant-animal mutualistic interactions (Beattie, L985; Keeler, L989). and ecology of the occupant ants in myrmecophytes have been studied in some plant genera, e. 9., Macaranga (Euphorbiaceae)(Fiala er al., 1989, 1994), Cecropia (Moraceae) (Janzen, 1969; Ferguson, 1995), Acacia (Leguminosae) (Janzen, 1966, 1967) and Myrmecod,ia (Rubiaceae) (Huxley, L978, 1982). Other occupants inhabiting myrmecophytes have been paid little attention, because both their species and individual numbers are usually very few. Dejean et al. (1996) recorded spiders in addition to some other and gastropods as occupants of. Scaphopetalum thonneri (Sterculiaceae). Scale and lycaenid larvae are known as myrmecophilous insects of Crematogaster ants occupying Macaranga spp. (Maschwitz et al., 1984; Fiala & Maschwitz, 1990). However, there is no report of the occupants except ants and myrmecophilous insects, though it is necessary to know the whole occupant fauna to clarify the detailed interactions between the hosts and symbionts. The epiphytic myrmecophytes in Hydnophytinae (Rubiaceae), have relatively small and compact bodies in contrast to tree myrmecophytes. It is easy to collect intact tuberous bodies together with all the occupants, and examining the complete occupant fauna is possible. The investigation of the occupants may play an important role in the elucidation of arboreal fauna, because it enables us to get specimens of cryptic animals in small spaces on the trees. Such animals do not fall from the tree crown by the insecticide spraying that is normal method of investigating canopy faunas. The result should reveal the role and significance of the cryptic animals in the arboreal biota. In this paper we report the fauna of all the occupants inhabiting the tuberous body of Hydnophytum moseleyanum Beccari (Rubiaceae: Hydnophytinae) in mangrove forests at Madang, Papua New Guinea. 94 T. MeSYAMA, O. KTTAPS & T. MATSUMOTO

MATERIALS & METHODS

Myrmecophyte Hydnophytum moseleyanum is distributed in and around New Guinea Is. This species usually grows on the trunk of host tree in open-canopied environments or in forest-edge (Fig. L, A & B). The lower part of the stem forms a swollen tuber which has a complex cavity system, which arboreal ants often inhabit (Fig. 1, C & D) @eccari, 1884; Jebb, 1991). They provide no food for associated ants directly or indirectly. There are fwo kinds of cavity in most species in Hydnophytinae (Janzen, 1974; Huxley & Jebb, 1991). The cavity of one type has smooth surface and that of the other has rough and warted surface. Huxley (1978) showed that Myrmecodia tuberosa in Papua New Guinea absorbs the nutrients through warted cavity surface from the debris stored by ants. Rickson (1979) also reported the same result on H. formicarium studied in Bako in East Malaysia. H. moseleyanum has the same type of cavities, and it is supposed that this species can also take nutrients ftom ant debris. Some cavities are connected together, but all the cavities are not connected completely (Jebb, 1985, 1991). Many entrance holes arise with the growth of plants. Though most entrance holes are about 5 mm in diameter, some holes in the lower part of tuber are often bigger than others.

Study area The study was conducted on a coastal region near the Christensen Research Institute (CRI) from June 1993 to November 1994. CRI is situated at 8 km northward of Madang town in Papua New Guinea (Fig. 2). The tropical climate prevails there, with little seasonal variation in temperature. The rainy season in this area is usually from December to April or May, and dry season from May to November. The survey was carried out in a coastal mangrove forest about 2-3 t{$ north of CRI. H. moseleyanum grows up on mangrove trees. Most trees measured 8-9 m in height, a few being over 20m. The roots of different trees got entangled in one another, and some boughs touched those of nearby trees. This allowed ants and the other animals to move from one tree to others in the forest.

Examination of occupants All the plants with diameter of 10 - 25 cm were collected from mangrove trees along the coast line in the study area. After cutting off the stem, the tuber of each ant-plant was cooled in a refrigerator for 2- 3 days, to immobilize all occupant animals. The tuber was sliced into pieces, then all ants and other occupants were picked up by forceps. They were fixed and stored in 807a alcohol and identified. The degree of symbiosis of the occupants (obligatory or facultative) was also determined. We checked for the presence / absence of the occupant animals outside myrmecophytes, such as in cracks of the bark, under the bark, or inside the dead hollow branches of mangrove trees.

RESULTS

A total of 483 individuals of I/. moseleyanum were examined, and 11 ant species in 9 genera and 39 other occupant species in 20 orders were found. Ants were found in 277 plants. Because all the plants without ants were always occupied by 1-3 species of blattellid cockroaches, plants without any animals were not found. Our previous study revealed that the most dominant ant, Philidris sp. 1., was monogynous and polydomous. Thus most plants were utilized as satellite nests without a foundress queen, containing only workers, broods and alates. The other ant species, except Tapinoma sp. and The diverse occupant fauna in epiphytic ant-plants in New Guinea 95

Fig. 1. A: H. moseleyanun on a bough of a mangrove tree. B: The whole plant. C: A section of H. maseleyanum frber. All occupants were removed frorn cavities. D: Occupants in cavities. Ants (Opisthopsrs sp.) in an upper cavity and termites (Nasutitermes sp.) in a lower cavity are shown.

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Monomorhun sp., might also have polydomous nest systems because queens were only rarely found. Colonies of Tapinoma sp. md Monomoriwn sp. always contained multiple queens. Thirty nine occupant species other than ants were found. These occupants can be classified into three groups. The first is a group of species not coexistingwith ants (Table l).'These animals inhabited plants not occupied by ants, or the cavities without ants inside the plants occupied by ants. The second is a group of opportunistic occupants found regardless of the presence / absence of ants 96 T. MaeYAMA, O. KITAPE & T. MNTSUMOTO

Table 1. The individual number of the occupant animal species not coexisting with ants detected from H, moseleyanum tubers. The individual numbers of the plants in which each species appeared are indicated in parentheses. Frequenry is shown as the rate of the plants which each occupant species appeared versus 483 investigated plants in total. The only number of workers are shown in ant species. Blank spaces mean no samples collected.

Occupants CockroachCockroachCockroachTermite Termite Beetle Beetle Beetle Beetle Order Blaftodea Blattodea Blattodea Isoptera Isoptera Coleoptera Coleoptera Coleoptera Coleoptera Family Blattellidae Blattellidae Blattellidae Termitidae Termitilae Scarabaellaellaieridae Nitidulidae Tenebrbnidae Species Baltasp.l Baltasp.2 sp. Nasutiter- Miuocero- Dnrnle- Alaussp. Cnpofu- Derispinsp. oaoaaoaoooomes sp. termes sp. pida sp. fus sP. Ant Occupanb (Formicidae) Philidris sp.1. 29 1.4 9 6872 814 1 4 16ees1 (1se) (22) (e) (n v) Q) (1) (2) Philidris sp.2 6 4 1623 (3) (2) (2) Tapinotusp. 10 4 ffil 2 2779(11) (6) (3) (1) (1) FORMICINAE Campnotrcsp. 8 5 7 5992 27638(fi) (5) (3) (1) (9) Colobopsissp. 7 1' 7476(6) (3) (1) Opbthopsismaunts 7 4 3 1 2445 (8) (2) (1) (1) G) Opisthopsis sp. 1 1 84o(s) (1) (1) Paratrechinasp. 2 547 s31 (3) (2) (1) MYRMECINAE Crenutogaster sp. U 21.23 1 8966(Gn (16) (3) (1) Monomoriumsp. 19 13863 78n(q (e) (1) (3) (1) PSEUDOMYRMECINAE Tetrqpnensp. 5 2 3 648(6) (1) (1) (1) Subtotal 1 37 21' 16391 73% 3 1 4 5 21,ffi4Q77) 6n QD (15) (21) (3) (2) (1) (2) (3) NoAntOccupants 7476 119 62 23735 7909 2 0 16 18 0 (206) (7e4) (45) (33) (26) (3) (1) (0) (7) (14) Total 7537 lffi 83 40126 3284 5 1 20 23 21S064 (483) (267) (66) (48) Gn (6) (3) (1) (e) On Frequency (%) 54.0 13.7 9.9 9.7 7.2 0.6 0.2 7.9 3.5 O= adul(s); A: larvae or nymphs; O: termites (workers, soldiers and nymphs).

(Table 2). They were present in both cavities with ants and without ants inside the plants occupied by ants. Also, they were found inside plants not occupied by ants. The third group includes occupants coexisting with ants (Table 3). They were always found from the cavities occupied by ants. All the occupant species including ants were also found from habitats outside the myrmecophytes, such as crack of the bark, gap under the bark or hollow in the dead branches of mangrove trees.

Occupants not coexisting with ants Tkenty-six species of occupant animals appeared not to coexist with ants (Table 1). A cockroach species in Blattellidae, Balta sp. 1, was found with high individual number and frequency (Fig. 3), though the other 2 species of blattellid cockroaches were less abundant. TWo termite species, The diverse occupant fauna in epiphytic ant-plants in New Guinea n

[Table L, continued 1]

Occupants Beetle Beetle Beetle Plant Hopper Shieldbug Wasp Cricket Psocid Moth Order Coleoptera Cohoptera Coleoptera Hemiptera Hemiptera Orthoptera Psocoptera kpidoptera Family Curculi- Cleridae Cleridae Delphacidae Pentato- Sphecidae Gryllidae Elipsocidae Noctuidae onidae midae Species Scolytw sp. sp. L sp. 2 sP. Poecilometis sp. sp. Pentncentrils sp. SP. SP. OAA o C OtrA CA CA Ant Occupants (Formicidae) DOLICHODERINAE Philidris sp.1 185 10 14 1,69951, (159) (7) (2) (2) (1) (4) Philidris sp.2 4 1623 (3) (1) Tapinoma sp. 11 1 2119 (11) (1) (1) (1) FORMICINAE Camponotus sp. 1 27638 (50) (1) Colobopsis sp. 2 1,476 (6) (1) Opistlnpsis mnurus zMs (8) Opisthopsrs sp. 840 (s) Parntrechina sp. s31 (3) MYRMECINAE Cremntogaster sp. 9 3 8966 (17) (2) (1) Monomorium sp. 1,827 (9) PSEUDOMYRMECINAE Tetraponern sp. 648 (6) Subtotal 0u510 13250 21,8064 (277) (0) (12) (2) (1) (0) (3) (2) (s) (o) No Ant Occupants 1100629 19 11 o (206) (1) (7) (0) (4) (2) (2) (1) (e) (10) Total 1445 72223 1,4 11 21,8064 (483) (1) (1e) (2) (s) (2) (s) (3) (14) (10) Frequency (%) 0.2 3.9 0.4 1.0 0.4 1.0 0.6 2.9 2.7

O= adult(s); D- pupae; A: larvae or nymphs.

Nasutitermes and Microceroterrnes,were sometimes found to inhabit the tuber. As any damage caused by the termites was not found, both species were not herbivores attacking the plants. It appears that they used the plants as nest sites. The other occupants were less abundant with low frequency. The crabs of Perusesanna were collected from myrmecophytes attached on the trunks of mangrove trees near the surface of the sea. As the only vertebrate animal, 2 batches of lizard eggs were observed, consisting of3 and 5 eggs respectively.

Opportunistic occupants Only 6 species belong to this category (Table 2). Isotomid springtails and porcellionid sow bugs were found frequently (69.67o and 26.77o each) in high numbers. The pill bugs in Armadillidae were also T. MenvAMA, O. Klrapn & T. MarsuMoro

[Table L, continued 2]

Occupants Earwig Spider Spider Spider Spider Centiped Crab Lizard Dermaptera Araneae Araneae Araneae Araneae Scolopendro- Decapoda Squamata morpha Family Labiduridae GnaphosidaeCtenizidae Araneidae Leptonetidae Scolopend- Grapsidae ridae Species sP. sp. sp. Aranus sp. sp. Otostigmus sp. Perisesarmn sp. sP. OAOAAOOAOAAV

DOUCHODERINAE Philidris sp.1 2 12 9 8 1,69951, (159) (2) (12) (e) (2) Philidris sp.2 1 rcnG) (1) Tapinoma sp. 1 1 1 21,79 (1,1) (1) (1) (1) FORMICINAE Camponotus sp. 9 27638 (s0) (7) Colobopsrs sp. 1 1 1,476 (6) (1) (1) Opisthopsis maurus 1 244s (8) (1) Opisthopsrs sp. 1 B4l0 (s) (1) Paratrechina sp. 12 s31 (3) (1) (1) MYRMECINAE Cremntogaster sp. 1 1 8e66 Qn (1) (1) Monomorium sp. 3 1827 (e) (3) PSEUDOMYRMECINAE Tetraponern sp. 1 648 (6) (1) Subtotal 327210 13 38 21,8064 (277) (3) (25) (2) (1) (0) (13) (2) (2)

No Ant Occupants 820 1610 1 o (206) (8) (1e) (1) (s) (8) (1) Total 11 472262348 21,8064 (483) (11) (44) (2) (2) (s) (21) (3) (2) Frequency (%) 2.3 9.1 0.4 0.4 1.0 4.3 0.5 0.4 O: adult(s); A- larvae or nymphsi V: eggs.

r00 Fig. 3. Frequency and individual l0 t0 oL number of Baln sp. I in plants D * t occupied and unoccupied by >60 5 z ants. (A) Frequency of Balta sp. H 6 3 E L found in H. moseleyanum. (B) E{0 E L E l& I Average number of indivi-duals E 20 H. 2 of Balta sp.l found in moseleyanum. Error bar = S. D. 0 {' * *' T-test, P<0.0001. Occupied Unoccugied Occupied Unoccupied N:277 N:206 N:277 N= 206 The diverse occupant fauna in epiphytic ant-plants in New Guinea 99

Table 2. The individual number of the occupant animal species regardless of ant existence detected from H. moseleyanum tubers. The individual numbers of the plants where each species appeared are indicated in parentheses. Frequency is shown as the rate of the plants which each occupant species appeared versus 483 investigated plants in total. The only number of worker ants are shown in ant species. Blank spaces mean no samples collected.

Occupants Springtail Mite Mite Pseudoocorpion Pill Bug Sow Bug Order Collembola Acari Acari Pseudoscorpiones Isopoda Isopoda Family Isotomidae Tydeidae Cheyletidae Chernetidae Armadillidae Porcellionidae

Species sP. sP. sP. sP. sP. sP. On Oa A CA On On Ant Occupants (Formicidae) DOLICHODERINAE

Philidris sp.1 79 4 15 1,6 1,69951, (159) (63) (2) (e) (14)

Philidris sp.z 2 1 rcnG) (2) (1) Tapinomn sp. 1,4 4 20 211e (11) (e) (3) (7) FORMICINAE

Camponotus sp. 62 1 1 1 9 27638 (50) (46) (1) (1) (1) (2)

Colobopsrs sp. 5 1 2 1,476 (6) (1) (1) (2) Opisthopsis mnurus 5 2Ms (8) (s) Opisthopsrs sp. 11 1 5 8410 (s) (s) (1) (2) Paratrechina sp. 5 2 2 2 s31 (3) (3) (2) (2) (1) MYRMECINAE Crematogaster sp. 22 3 9 8e66 0n (8) (1) (6) Monomorium sp. 6 1 1 9 1,827 (9) (s) (1) (1) (3) PSEUDOMYRMECINAE Tetraponerfr sp. 4 648 (6) (2)

Subtotal 211, 1.6 2 4 28 & 218064 (277) (147) (11) (2) (2) (16) (3s)

No Ant Occupants 691 27 2 3 121, 233 o (206) (18e) QN (1) (1) (57) (e4)

Total 902 43 4 7 1,49 297 21,8064 (483) (336) (28) (3) (3) (73) (1,29)

Frequency (%) 69.6 5.8 0.6 0.6 15.1 26.7

O= adults; A= nymphs. numerous, but not so frequent (ll.lVo). The other occupants, two mito species and one pseudoscorpion species, were found rarely and in small numbers.

Occupants coexisting with ants Seven species were always found from the cavities with ants (Table 3). Though all of them were not so frequent, many maggots were seen in the debris stored by occupant ants in the warted cavities of plants. Of 11 species of occupant ants, Philidris sp. 1, Camponotus sp., Crematogasler sp. and Philidris sp. 2 were observed to store their debris on the wall of warted cavities. The maggots and 100 T. ManYAMA, O. KTTNOE & T. MATSUMOTO

Table 3. The individual number of the occupant animal species coexisting with ants detected from H. moseleyanum tubers. The individual numbers of the plants which each species appeared are indicated in parentheses. Frequenry is shown as the rate of the plants which each oiiupant species appeared vercus 277 investigated plants occupied by ant species. The only numler of worker ants are shown in ant species. Blank spaces mean no samples collected'

Occupants Cricket Was Maggot Pit Scale Beetle Silverfish Stylopid Order Orthoptera Hymenoptera Diptera Hemiptera Coleoptera Thysanura Strepsiptera Family Gryllidae Eucharitidae Cerococcidae Psephenidae Nicolettiidae Myrmecolacidae Species Myrmecophy- Rhipipalloidea Ius arboreus neu)guinensis l-spp?.1 sP. sP. SP. SP. r\nr-rnnnnnr)n.) Ant Occupants (Formicidae) DOLICHODERINAE Philidris sp.1 46 476 51 283 1,69951, (159) (27) (1s2) (6) (13) (3) Philidris sp.2 2 5 rcnG) (1) (2) Tapinoma sp. 2 1 21,19 (11) (2) (1) FORMICINAE Camponotus sp. 17 49 1,1,4 9 27638 (s0) (7) (23) (43) (7) Colobopsrs sp. 1 1,476 (6) (1) Opisthopsis mnurus 1 2445 (8) (1) Opistlnpsis sp. 840 (s) Paratrechina sp. 2 531 (3) (1) MYRMECINAE Crematogaster sp. 5 9 1 8956 (17) (4) (4) (1) Monomorium sp. 1,827 (9) PSEUDOMYRMECINAE Tetraponerfr sp. 648 (6)

Total 72 49 604 51387 1 218064 (277) (41) (23) (201) (6) (21) (6) (1) Frequency (%) 8.s 4.8 41.6 1,.2 4.3 1,.2 0.2

O= adult(s); E= pupae; A= larvae. psephenid larvae were always found out in the debris of these ant species. Because of the confusion of classification of New Guinean Diptera, the maggots could not be identified even at level. There is a possibility that these maggots include the larvae of more than 1 dipteran species. Minute crickets, Myrmecophylus arboreus, and nicolettid silverfishes were thought to be commensals. The wasp Rhipipalloidea newguinensis and a myrmecolacid stylopid were endoparasites; pupae of Rhipipalloidea newguinensis were found only from the inside of cocoons of Camponotus sp. A stylopid appeared in the abdomen of a worker ant of Tapinoma sp. The cerococcid pit scales were found out on the smooth cavitywallofplanboccupiedbyPftilidrissp.l. Theywerenotabundant,andtheirfrequencywirsquitelow

DISCUSSION

A diverse occupant species appeared in a single myrmecophyte species, H. moseleyanum. ln total 50 occupant species are reported in this study (Table 1, 2, 3). Such a diverse fauna has not so far been The diverse occupant fauna in epiphytic ant-plants in New Guinea 101 reported for other myrmecophytes. There was no specialist for H. moseleyanum because all the occupants were found in arboreal habitats outside the myrmecophytes. We consider that the occupants live in facultative symbioses with ^EL moseleyanum plants. However, Philidris sp. 1, which is the most dominant ant and has a considerably large biomass, gives a benefit to H. moseleyanum (Maeyama & Matsumoto, in prep.). Host plants occupied by this ant species have a greater average seed weight, and the effect is caused by the supply ofnutrition from the ant debris. Similarly, cockroach species may provide a benefit for the plants, because they usually store their debris in the cavities of plants. These debris are stored in both smooth and warted cavities, and the plants are thought to absorb nutrients through the wall ofwarted cavities. Because cockroach species, especially Balta sp. L, frequently appear in H. moseleyanum inhigh numbers (Fig. 3), it is plausible that they considerably improve the nutritional condition of the plants. Most of the occupants coexisting with ants are thought to be myrmecophilous species. The cricket Myrmecophylus arboreus and nicolettid silverfish may be snatchers or commensals of ants. These species do not show strict host specificity (Table 3). The eucharitid wasp Rhipipalloidea newguinensis and myrmecolacid stylopid are endoparasites. The former is specialized in Camponotrs sp. and the latter may be specialized in Tapinoma sp. H the maggots and psephenid larvae are the scavengers of ant debris, they are regarded as commensals of ants which stored the debris inside their nest. Cerococcid pit scales appeared in the nests of Philidres sp. 1. In the myrmecophytes Macaranga spp., it is reported that the coccoid species in hollow spaces of internodes (domatia) were mutualists of the occupant ants Crematogaster spp. (Fiala & Maschwitz, 1990). The ants utilize honeydew secreted by the coccoids as an important food source. However, our previous study revealed that the main food sovce of Philidris sp. 1 was honeydew secreted by another coccoid species attached to the tips ofbranches ofmangrove trees (Maeyama, 1995). Since Philidris sp. 1. would not utilize the cerococcid pit scales as a main food source, it is unknown whether the cerococcids are mutualists of Philidris sp. 1. Most of the occupant species are proposed to be facultative generalist commensals of both myrmecophyte and ant species. We consider that they all are secondary users of the space inside the myrmecophytes that enter the plants by chance, and not associates living in obligatory symbioses with myrmecophyte and ant species. The myrmecophytes provide arboreal animals with shelters and moisture that are generally limited resources especially in mangrove forest regions (see also Fiala & Maschwitz, 1992). It is suggested that the myrmecophyte, H. moseleyanum, plays an important role in the maintenance of biodiversity in arboreal environments.

ACKNOWLEDGEMENTS We deeply thank Dr. M. H. P. Jebb and Dr. L. Orsak, previous and present directors of the Christensen Research Institute in Papua New Guinea, for appropriate advice and various helps. We are also grateful to Dr. L. M. Roth for the identification of all cockroach species, and to Dr. M. Terayama for the identification of all the species of ants, wasps, crickets and a stylopid. The manuscript benefited by comments from Mr. Nathan In. Thanks are also extended to the members of the Matsumoto laboratory for their encouragement and useful discussion. T. M. and O. K. were supported by JSPS Research Fellowships for Young Scientists.

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F., eds., Ant-plant Interactions, 37 4-389. Oxford University Press, Oxford' Keeler, K. H. 1989. Ant-plant interactions. 1z: Abrahamson, W. G., ed., Plant-animal Interactions, 207-242. McGraw-Hill, New York. Kiew, R. & Anthonysamy, S. 1987. A comparative study of vascular epiphytes in three epiphyte-rich habitats at Ulu Endau, Johore Malaysia. Malayan Nature J' 41: 303-316. Maeyama, T. 1995. Ecology and symbiotic relationship between ants and rubiacerous epiphytic ant- plants. Master's thesis, University of Tokyo, Tokyo' Maschwitz, U., Schroth M., H?inal, H. & Pong, T. Y. 1984. Lycaenids parasitizing symbiotic plant-ant partnerships. Oecologia 64: 78-80. Rickson, F. R. 1979. Absorption of animal tissue breakdown products into a plant stem-the feeding of a plant by ants.Amen J. Bot.66:87-90. Received APnl29,l997 Accepted Jume25,1997 The diverse occupant fauna in epiphytic ant-plants in New Guinea 103

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