Journal of Tropical Forest Science ll(3):537-547 (1999)

EDGE EFFECTS ON AMBROSIA 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 (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, 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 a e margin of the reserve.

Key words: Edge effects - forest fragmentation - - 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 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 environmentao t 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. Species richness (numbe speciesf ro ) (S), dominance indice Berger-Parkef so r Simpsod (dan ) Shanoe nth (D)d nan , inde diversitf xo y (H') (Magurran 1988) were calculated for each trap site. The values were tested for correlation with othee th f trao r p sites using Kendall coefficient f rano s k correlation (T ). Ran k abundance plots (Magurran 1988) were also compared among sites. Species similarity between pair f trao s p sites were measured wite Sorenseth h n (quantitative Jaccard an ) d indices (Magurran 1988). Trapping of the most abundant species, Xylosandrus crassiusculus, was carried out again fro Novembe8 m2 Decembe5 o rt r 199 sitet 3a s 3-7 eact A . h siten te , traps were placed in a transect at 10-m intervals. Trapped beetles were collected threr evero o ey tw day countedd san . Regression analysi transformeg lo uses n wa sdo d number . crassiusculusX f so per trap per week, trapped in the forest, as a function of minimum distance fro forese mth t edge. Data obtaine March/Apridn i November/Decemben i d lan r were treated separately. Journal of Tropical Forest Science ll(3):537-547 (1999) 541

clarif To verticathe y l distributio crassiusculusX. of nforest the in , trapping wit ethanoe hth l conductetras pwa three th en d o canop y tower 1993n s i eacn O .h tower, four traps were placed in March/April at heights of 1, 13, 25 and 32 m above the ground, and nine traps in November/December at heights of 0.8, 4.6,8.4,12.2,16.1,19.9,23.7,27. 31.4md 6an eacn I . h case, trappin carries gwa d out for three consecutive weeks.

Results

Species diversity tribethe of Xyleborini (Scolytidae)

Altogether, 31 species representing 5 genera of the tribe Xyleborini were collected at sites 1-5 in March/April (Table 1). Of the 8 most frequently captured species with 20 or more individuals, only Xylosandrus crassiusculus showed a significant trend in relative abundance along the gradient from the core (Site 1) to the boundar 0.05)< p , 1.005 .y= = T (Sit ( n , ) e5

Table 1. Total number of ambrosia beetles of the tribe Xyleborini captured five inth e trap site Pason si h Forest Reserve, March/April 1993

Species Sit e1 Sit e2 Sit e3 Sit e4 Sit e5 Total

Arixyleborus granifer (Eichhoff) 1 0 2 2 0 5 Arixyleborus granulifer (Eggers) 10 8 11 7 30 66 Arixyleborus minor (Eggers) 0 3 0 0 0 3 Arixyleborus rugosipes (Hopkins) 3 7 7 14 11 42 Cnestus1 . sp 0 0 0 0 2 2 Steptocranus. sp 1 0 1 1 1 4 affinis (Eichhoff) 7 6 8 7 11 39 Xyleborus amphicranulus (Eggers) 1 0 0 0 0 1 Xyleborus andrewesi (Blandford) 31 4 3 3 2 43 Xyleborus concisus (Blandford) 0 1 1 0 0 2 Xyleborus ?emarginatus (Eichhoff) 1 1 0 0 0 2 Xyleborus exiguus (Walker) 5 5 1 6 2 19 Xyleborus globus (Blandford) 0 1 0 1 2 4 Xyleborus lewisi (Blandford) 0 1 0 0 0 1 Xyleborus ?tuberculosus (Browne) 7 4 7 4 4 26 Xyleborus vestitus (Schedl) 2 1 0 4 0 7 Xyleborus volvulus (Fabricius) 2 1 0 3 3 9 Xyleborus2 . sp 5 1 3 6 1 16 Xyleborus3 . sp 7 1 2 5 7 22 Xyleborus sp. 7 1 0 1 0 0 2 Xyleborus sp. 8 0 0 1 0 0 1 Xyleborus0 1 . sp 0 0 1 0 0 1 Xyleborus1 1 . sp 0 0 0 1 0 1 Xyleborus sp. 12 0 0 0 2 0 2 Xyleborus sp. 14 2 3 2 2 2 11 Xyleborus sp. 18 0 0 0 0 1 1 ?Xyleborus9 1 . sp 0 0 0 1 0 1 ?Xyleborus sp. 20 2 0 0 0 1 3 Xylosandrus compactus (Eichoff) 1 1 0 1 1 4 Xylosandrus crassiusculus (Motschulsky) 25 74 96 237 609 1041 Xylosandrus morigerus (Blandford) 7 9 1 0 3 20

Total 121 132 148 307 693 1401 542 Journal of Tropical Forest Science ll(3):537-547 (1999)

Species richness (number of species) (S) was not significantly changed along the trap sites (Table 2). Dominance indices of Berger-Parker (d) and Simpson l specieal (Dr fo )s combined increased significantly alon e gradiength t from sito t e5 (Tabl1 . Howevere2) , excludin e mosgth t abundant species, X. crassiusculus, which constitute increasinn da g proportio f totano l individuals trapped from site 1 (20.7%) to site 5 (87.9%), the dominance indices were almost constant among the trap sites (Table 2). Also, rank abundance plots were virtuall ye tra identicath p l siteal r sfo l whe . crassiusculusnX excludes wa d (Figure 2).

Tabl . e2 Diversit y indiceXylerobine th r sfo i capture five th e n tradi p sites (recalculated values excluding Xylosandrus crassiusculus are shown in parentheses), and corresponding Kendall correlation coefficient) (T s

Site1 Site 2 Site 3 Site 4 Site 5

Species richness 20 18 17 19 19 -0.53 (numbe speciesf ro ) S ,

Berger-Parker index 0.26 0.56 0.65 0.77 0.88 1.00 <0.05 of dominance (d) (0.32) (0.16) (0.21) (0.20) (0.36) (0.20) (ns)

Simpson's index 0.13 0.33 0.43 0.60 0.77 1.00 <0.05 of dominanc) e(D (0.14) (0.08) (0.10) (0.08) (0.17) (0.20) (ns)

Shannon index 2.40 0.55 0.32 1.13 0.64 -0.20 ns f diversito y (H') (2.39) (2.57) (2.39) (2.60) (2.20) (-0.11) (ns)

Site1 Site 2 Site 3 Site 4 Site 5 1000

0 0 0 0 2 2 10 0 1 0 0 2 10 Species rank

Figur . Rane2 k abundanc efive plotth e r trasfo pforeste siteth n si . Closed symbols represent Xylosandrus crassiusculus. Journal o3 f Tropical54 Forest Science ll(3):537-547 (1999)

Species similarity measured with the Sorensen and Jaccard indices varied only slightly between pair f traso p sites (Tabl , indicatine3) g tha tmarke o thern s ewa d disharmony in species composition between the core and boundary.

Table 3. Sorensen (upper right) and Jaccard (lower left) indices of species similarity between trap sites

Site 1 Site 2 Site 3 Site 4 Site 5

Site 1 . 0.769 0.757 0.769 0.789 Site 2 0.625 - 0.667 0.737 0.757 Site 3 0.609 0.500 - 0.667 0.686 Site 4 0.625 0.583 0.500 - 0.757 Site 5 0.652 0.609 0.522 0.609 -

Abundance of Xylosandrus crassiusculus

e numbe . Th crassiusculusX f o r capture r trar wee dplottepe s p pe kwa a s da functio minimue th f no m distanc eacf eo h site fro plantation-forese mth t boundary foreste th (Figurmea g n I lo , . n e3) number crassiusculus. X f so decreased linearly with distance fro e foresmth t edge bot March/Aprin hi n i d an l ) (site5 - 1 s November/December (sites 3-6) (Table 4). However, the number of this species trappe equivalens dwa t betwee forese nth plantatiositt e a t eth edg6 sitn d i e7 an n over the trapping period in November/December (t-test on log transformed data, t = 0.22,df=18,p>0.5).

Table 4. Regression of log (No. Xylosandrus crassiusculus per trap per week) on minimum distance from the forest edge in km

Y-intercept Slope Sampling period N al^95%CI b 1 £ 95% CI r2 P(P = 0)

March/April 5 1.1010.32 -1.2110.45 0.961 <0.01 November/December 4 1.6610.62 -2.2611.89 0.930 <0.05

Vertical distribution of Xylosandrus crassiusculus

e canopth n yO towers nea e number th crassiusculussit. , X e3 f o r trapped showed an inverse relationship with the height at which the traps were suspended (Figure 4). More than 70% of the total number trapped (8 out of November/Decembern i 6 2 f o March/Apri n t i 9 ou 8 1 d an l ) were belom w5 from the ground. 544 Journal of Tropical Forest Science ll(3):537-547 (1999)

> ( 6 07 t

10.0- t 5

1.0-

Palm Plantation Forest Reserve 1 n 1 - -1.00 -0.50 0.00 0.50 1.00 1.50 Minimum distance from the forest edge (km)

Figure 3. Abundances (mean±s.e.) of Xylosandrus crassiusculus at varying minimum distances from the forest edge. The latter is the shortest distance from the centre of each sampling transect to the forest edge. The y-axis is shown in log scale. Closed circles represent trapping carried out in March/April traps)8 1 (n= ; open circles represent trapping carrie Novembern i t dou / Decembe traps)0 =1 n .( r Number strae refeth p o sitet r s show Figurn i . e1

1.5

1.0 H

o o 0.0 10 20 30 Height (m)

Figure 4. Abundances of Xylosandrus crassiusculus at varying heights above the ground. Closed circles represent trapping carrieMarch/Apriln i t dou ; open circles represent trapping carried out in November/December (Kedall correlation coefficient, T = -0.884, n = 9, p < 0.01). Journal o5 f Tropical54 Forest Science ll(3):537-547 (1999)

Discussion

Species richnes d compositioan s f ambrosio n a beetle assemblages wert no e considerably changed along a gradient from the core to the boundary in Pasoh Forest Reserve e buffeTh .t bee r no zon nd disturbeeha d artificially since large dipterocarps and legumes were selectively logged in the mid-1950s and, thus, the forest structure had mostly recovered (cf. Wong 1986). In general, ambrosia beetles are polyphagous (Browne 1961); when host selection occurs, it is usually at plant family level. In Malaysia, most host-specific species are specialists on the Dipterocarpaceae, the most dominant tree family in lowland and hill dipterocarp forest (Beaver & Browne 1978). Thus, in general, ambrosia beetles may be tolerant of minor changes in forest structure and tree species composition. Amon specie1 3 e ambrosigf th s o a beetles trappe thidn i s study, onl crassiusculusyX showe dclosa e relationship betwee abundancs nit locatioe th d trappinf ean no g sites, increasing exponentially in number from the core area to the forest edge, and being super-dominan boundarye th t ta . Toda (1992) noted tha distributioe th t n height of canopy dwelling insects tends to be lower at the forest margin. However, this was not the case with X. crassiusculus, because it was trapped mainly just above the forest floor, even deep in the forest, whilst various other species of ambrosia beetles were trapped in the canopy (Maeto et al, unpublished data). Tree mortality usually increase somo st e degree near forest edges (Williams- Linera 1990, Youn Mitchelg& l 1994). This could caus increasn ea ambrosif eo a beetles in the boundary, but it is unlikely that only one species would thrive with the falling of various tree species. Furthermore, no striking deterioration of forest structur bees eha n noteboundare th t da Pasof yo h Forest Reserve (Wong 1986). In the plantation, X. crassiusculus breeds in fallen leaf stalks of oil palm trees (Maeto, pers. observation). The ability of this species to disperse is not known, but many scolytid beetles are strong fliers; for example, the Ips typographus was abl o disperst e e several kilometres (Weslie Lindelo& n w 1990). Thust i seems most likely that the population of X. crassiusculus in the forest is augmented b larga y e beetleinflue th f x o pall s oi fro me mplantationth . observee Th d gradien abundance th n i t . crassiusculusX f eo alsy influe ob ma - enced by the presence of previously disturbed forest at the margin of the reserve. Although there has not been any logging in the 1980s and 1990s, some changes in tree composition, woody litte d lighan r t environmen e likelar t havo yt e remained in the buffer zone. Most scolytid Wesf so t Malaysi endemie aar distributer co d withi range nth f eo India, Indochina, Sundaland, Philippines, Sulawesi and New Guinea (Browne 1961, Beave Brownr& e 1978) t XylosandrusBu . crassiusculus, until recently known Xyleboruss a semiopacus (Wood 1969,1982) vers ,i y widely distributed throughout Africae th Asiatid an n c tropics Pacifie th , Koreo ct JapaIslandsd p u aan d n an , (Beaver & Browne 1978, Nobuchi 1985), and it has also been recorded from South Carolina (WooA ,US d 1982) Samoan I . , this specie infrequentls si y encountered raie inth n forest whils commos i t i t cultivaten ni d areas (Beaver 1976). These 6 54 Journal of Tropical Forest Science ll(3):537-547 (1999)

observations imply that X. crassiusculus is a strong disperser, and prefers disturbed to primary forests. Xylosandrus crassiusculus has been recorded from tree species in more than 30 families, including Dipterocarpaceae, Leguminosa Palmaed t usuallei an d an ,y attacks smal diameten li stemm branchec d 5 san 9. r - (Brown 5 s1. e 1961, Beaver& Browne 1978). It sometimes attacks living trees (Browne 1961) and, in West Africa, it has been a pest causing high mortality of transplanted trees in young plantations of Khaya (Meliaceae) and Aucoumea (Burseraceae) (Browne 1963). Thus, some- what weakened seedlings and saplings of various tree species can be attacked by this . Although there wer obviouo en s biological change forese th n sti attributedo t the influx of X. crassiusculus, it is possible that this insect carries microorganisms fro plantatioe mth n deep int primare oth y forest ambrosis a , a beetle knowe sar n carro t treeo yt s various fung bacteriad an i , including possible pathogens (e.g. Webe McPhersor& n 1984, Beaver 1989). More attention needgivee b o o nt st such insect invasion of forest remnants from the surrounding man-modified environment.

Acknowledgements

W gratefue late . Nobuchear e identificatio th A s e helth o hi t n lpr i ifo f no ambrosia beetles e assistanc Th .. Konish. HattorT K f d o ean n settinii i e gth insect trap s i gratefulls y acknowledged e alsW .o thank three anonymous reviewers for valuable comments on the manuscript. This study was part of a joint research project betwee e Foresnth t Research Institut f Malaysiaeo , Universiti Putra Malaysia and the National Institute for Environmental Studies of Japan unde Globae rth l Environment Research Programme funde e Japath y ndb Environ- ment Agency (Grant No. E-1).

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