Journal of Tropical Forest Science ll(3):537-547 (1999) EDGE EFFECTS ON AMBROSIA BEETLE ASSEMBLAGES IN A LOWLAND RAIN FOREST, BORDERIN PALL GOI M PLANTATIONS, IN PENINSULAR MALAYSIA K. Maeto, Shikoku Research Centre, Forestry and Forest Products Research Institute, Asakura-Nishimachi 2-915, Kochi 780-8077, Japan K. Fukuyama Hokkaido Research Centre, Forestry and Forest Products Research Institute, Hitsujigaoka 7, Sapporo 062, Japan & . KirtoLG . n Forest Research Institute Malaysia, Kepong, 52109 Kuala Lumpur, Malaysia Received April 1996_____________________________________________ MAETO , FUKUYAMAK. , KIRTON& . K ,. 1999 G . L ,. Edge effect ambrosin o s a beetle assemblage lowlana n i s d rain forest, borderin l paloi g m plantationsn i , Peninsular Malaysia. Investigations were made on the edge effects on ambrosia beetle assemblage Pason i s h Forest Reserve lowlana , d rain fores Peninsulan i t r Malaysia, which largely borders oil palm plantations (Elaeis guineensis) established in the 1970s. Species richness and composition of the ambrosia beetles (Scolytidae: Xyleborini) sampled with ethanol traps were not considerably changed along a gradient from e corth ee boundar th are e foresto t ath f o y. However a polyphagou, s species, Xylosandrus crassiusculus, consistently increased in number from the core to the forest edge, being super-dominant at the boundary. It was as abundant at the surrounding oil palm plantatio forese th n ti boundarys na , consistent wit hypothesie hth s that there is a large influx of X. crassiusculus from oil palm plantation to forest reserve. The populatio alsolessea y o t ma ,n r extent enhancee b , foresy b d t disturbance th t ea margin of the reserve. Key words: Edge effects - forest fragmentation - insects - ambrosia beetles - Scolytidae - oil palm - tropical rain forest - Pasoh MAETO FUKUYAMA, K. , KIRTON& . ,K , L.G. 1999. Kesan tepi terhadap kumpulan kumbang ambrosi i hutaad n hujan tanah pamah yang bersempadan dengan ladang kelapa sawi Semenanjuni td g Malaysia. Penyelidikan dijalankan mengenai kesan tepi terhadap kumpulan kumbang ambrosia di Hutan Simpan Pasoh, iaitu hutan hujan tanah pama i Semenanjunhd g Malaysia, yang bersempadan dengan ladang kelapa sawit (Elaeis guineensis) yang ditubuhkan pada tahun 1970-an. Kekayaan spesien sda komposisi kulatambrosia (Scolytidae: Xyleborini) disampel dengan perangkap etanol 538 Journal of Tropical Forest Science ll(3):537-547 (1999) yang serup i sepanjanad g cerun dari kawasan tengah hinggala sempadae hk n hutan tersebut. Bagaimanapun, bilangan sejenis spesies polifagus, Xylosandrus crassiusculus, bertambah secara tetap di bahagian tengah hingga ke tepi hutan, dan menjadi super- unggul di sempadan. la terdapat dengan banyaknya di sekitar ladang kelapa sawit dan sempadan hutan, sejajar dengan hipotesis bahawa terdapat kebanjiran masuk X. crassiusculus dari ladang kelapa sawi hutae k t n simpan. Populasi juga mungkin bertambah sebahagian kecilnya akibat kerosaka i pinggind r hutan simpan. Introduction Plant and animal populations in fragmented habitats are not only subdivided and reduced in size, but are also exposed to abiotic and biotic changes associated with artificially induced edge r adjacenso t environmental conditions (e.g. Williams- Linera 1990, Laurance 1991, Angelstam 1992). Informatio influence th n no f eo edge effects is essential in forest conservation programmes. Edge effects in fragments include changes in microclimate, light conditions and wind-shear forces which can alter forest structure and composition (Williams-Linera 1990, Laurance 1991, Young & Mitchell 1994) and, subsequently, alter assemblages of small mammals, bird insectd san s (e.g. Wong 1986, Klein 1989, Laurance 1994). Further- more e invasioth , f organismno s originating from bordering habitat bees sha n known to affect birds in interior forest (Wilcove 1985). It also leads to an increase in seed predatio beecf no h (Nilsso Wastljunn& g 1987). Peninsulan I r Malaysia, forest conversio agricultureo nt , mainl l paloi mo yt (Elaeis guineensis) and rubber (Hevea brasiliensis), intensified during the period from 1971 to 1990 when a total of 1.64 million ha of lowland rain forests were cleared (Manokaran 1992). Remaining lowland forests, including some primary forest reserves, have been fragmente varyino dt g degreeoftee ar nd surroundesan y db plantations of oil palm and rubber. With understorey bird dund an s g beetles, species richness decreasee th t sa boundary of a lowland forest reserve (Wong 1986, Tsubaki & Intachat 1994). Further studie requiree sar determindo t e edge effect othen so r animal assemblages in fragmented forests. Ambrosia beetle e ric speciear sn hi abundand an s tropican i t l rain forests (Browne 1961, Beaver 1979). Their larvae feed on symbiotic fungi growing on the wall gallerief so s excavate parene th y db t beetlwooe th treef dn eo bushesi d san . Dependin dyinn go weakener go d part treesf so , the expectee yar sensitive b o dt e o environmentat l change raie th n n sforesti additionn I . , since they carry various microorganisms including possibly, pathogen treeo st s (Beaver 1989), vegetation structure of a virgin forest may be affected by the inflow of beetles from adjacent disturbed areas. Ambrosia beetles are easily sampled with traps baited with ethanol (e.g. Beaver & Browne 1978). In this study, we used such traps and addressed the following e specieth questions e sAr richnes) (1 : d compositioan s f ambrosino a beetles different between the core area and the boundary of a protected forest? (2) Are any particular species notably abundant or sparse at the boundary? (3) What makes the pattern? Journal of9 Tropical53 Forest Science ll(3):537-547 (1999) Materials and methods Study area This stud conductes ywa Pason di h Forest Reserve, whic locates hi d m abouk 0 14 t southeast of Kuala Lumpur in Peninsular Malaysia (2° 59'N, 102°18'W), covering 2450 ha in area. It consists of a core of about 600 ha primary lowland forest (80-12 a.s.l.)0m buffea , r zon f regeneratineo g forest whic partialls hwa d yan selectively logged on three sides of the core in the mid-1950s, and primary hill forest on the northeastern side of the core. In the early 1970s, the forest exterior to the buffer zone was converted to oil palm plantations, although some discontinuous patches of secondary growth occur along streams. e uppeTh r canop primare th f yo y fores dominates i t merantd re y db i (Shorea section Muticae, especially S. leprosula, S. acuminata and 5. macroptera). In a 50-ha permanent plot in the core area, there were 814 tree species (Manokaran et al. 1992). The mean annual rainfall at Pasoh is roughly 2000 mm, usually with a rain-free period of 20-25 days either between January and March or between July and August (Kochummen et al. 1990). In the year that this study was carried t (1993)ou , tota rain-frea l d rainfalan , 170s e wa periol7mm d (more tha0 1 n continuous days with less than 1.0mm daily rainfall) occurred from late January to early February (Saifuddin et al. 1994). Five sampling sites along the gradient from the core area to the boundary l paloi m(sitee th plantatio sn o 1-5) e e on , nfores- th n i t e edgon ed (sitan ) e6 plantation (site 7) were established (Figure 1). Although the sites were located along or near main trails, the width of which was 2-5 m in the buffer zone and 1-2 m in the primary forest, there was no visible disturbance of the vegetation along the trails, and the tree canopies formed a closed cover above them. Near site 3, there were three canopy towers (32-40 m in height) 10 m apart from each other whicn o , verticae hth l distributio beetlef no investigateds swa . Sampling and analysis Sampling was carried out by setting up black plastic traps consisting of two vertical collision areaplatesn i basa,n i slotte cm , 0 m eaclc widt57 0 hd3 d inthan o 2 each other at right-angles, with a roof over the collision plates and a collecting vessel between them (Fukuyama et al. 1994). The vessel was filled with 500 ml of wate detergen f sorbiwhicg o o rt l 5 m 0. c h1 d aci antisepticn tan d(a addeds )wa A . small plastic vial (4 cm in diameter and 8 cm deep) containing absorbent cotton with 25 ml of 99% ethanol was wired just beneath the centre of the roof. The s piercevialwa d with four 2-mm diameter hole alloo t s w gradual evaporatiof no the ethanol. After one week of trapping, 10ml of 99% ethanol was added into the vial. The traps were 1.5 m above the ground. 540 Journal of Tropical Forest Science 11(3) :537-547 (1999) - -* Sampling transect T Canopy tower Mai— n trail Figure 1. Map showing Pasoh Forest Reserve (inset) and the study area. Trap sites were numbered along the gradient from the core area of the forest into the oil palm plantation. The shaded area shows the approximate extent of the regenerating logged-over forest. From 26 March to 16 April 1993 (3 weeks), trapping was carried out at five samplin gforese siteth n sti (sites 1-5, Figureact A h. sitee1) trap8 1 , s were placed in a transect at 10-m intervals. Trapped insects were collected every week, preserve ethanon di lated lan r mounted. Ambrosia beetle tribe th ef s o Xyleborin i (Scolytidae), which were all females as males of the tribe do not leave the vicinity parene ofth t nest (Browne 1961), were later identified. Voucher specimens have been deposite Forese th n tdi Researc h Institut e Nationae th Malaysi n i d l an a Institute of Agro-Environmental Sciences in Tsukuba, Japan.