Efficiency and Behavior of Insect Visitors on Pollination of Agarwood (Aquilaria crassna Pierre ex Lec.) Flowers: a Comparison of Natural and Plantation Stands W. Tasen1,2, K. Ogata1, S. Tangmitcharoen3, O. Tadauchi4 and M. Thakeaw5 1Kyushu University, Fukuoka, Japan 2Kasetsart University, Bangkok, Thailand 3Royal Forest Department, Bangkok, Thailand 4Kyushu University, Fukuoka, Japan 5Department of National Parks, Wildlife and Plant Conservation Bangkok, Thailand คลังความรู้ดิจิทัล มหาวิทยาลัยเกษตรศาสตร์ Abstract The efficiency and behaviour of insect visitors to agarwood (Aquilaria crassna Pierre ex Lec.) was investigated in a natural forest at Khao Yai National Park and a plantation in Trat province, Thailand. This study investigated the diversity and abundance of flower visitors, their behaviour and the effectiveness of the major insect visitors on agarwood flowers. The data was collected during the flowering season in March, April and May from 2006 to 2008. A total of 103 insect species was found, comprising 34 families of 4 orders. Among this figure, Lepidoptera (61 species) recorded the highest number of species found on the flowers, followed by Hymenoptera (26 species). Coleoptera and Diptera recorded only eight species each. In the natural forest, higher species diversity and species richness of the insect visitors were observed than in the plantation. The highest frequency of individual visits on the flowers was observed during the times of 20.00 to 22.00 hours, and 10.00 to 12.00 hours. In contrast, the lowest activity on the flowers was found during 16.00 to 18.00 hours. The efficiency of the major insect visitors was estimated from the mean number of pollen grains deposited on the proboscis of each visiting insect. Parallelia rigidistria (Noctuidae, Lepidoptera) recorded the highest number of pollen grains on the proboscis with 25.57±8.61 (n=7). Endotricha species (Pyralidae, Lepidoptera) were the most common in terms of Proceedings of the FORTROP II: Tropical Forestry Change in a Changing World, 17-20 November 2008, Kasetsart University, Bangkok, Thailand 134 FORTROP II: Tropical Forestry Change in a Changing World frequency and abundance in both areas having pollen deposited on the proboscis at a rate of 16.29±5.36 (n=9) grains per individual. Keywords: pollination, Aquilaria crassna, insect visitors, plantation, natural forest Introduction Agarwood (Aquilaria crassna Pierre ex Lec.) is one of the most important commercial, resinous, heartwood species. The raw material of the wood is คลังความรู้ดิจิทัลfamous for มหาวิทยาลัยเกษตรศาสตร์ producing perfume and incense in the Middle East. It is a member of the family Thymelaeaceae, which is native to continental Southeast Asia and found throughout tropical forests in many countries, including Cambodia, Laos, Thailand and Vietnam (Phengklai and Khamsai, 1985; Materials and Methods Nghia, 1998). Study Sites Traditionally, resin is mainly extracted from the genus Aquilaria including A. crassna, generally found in natural forests. It is considered to have a high quality and commands a high price due to its immune response to fungal attack (Nghia, 1998). In recent years, its demand has increased, leading to it being classified as ‘critically endangered’ as defined by the criteria of the IUCN red list and it is listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) of Wild Fauna and Flora (Nghia, 1998). Therefore, without a good management system, A. crassna may become extinct in the near future. To overcome this problem, the rate of establishment of agarwood plantation has been expanded rapidly in Thailand and neighbouring countries, in order to successfully produce high quality seed. However, the germination rate is one of the major problems because the rate of seed viability is low and has been found to decrease to 25% in the third week (Khangsap and Wachrinrat, 2005). Tissue culture could be an alternative means of coping with the germination rate problem. However, this technique requires high investment and is still in the developmental phase. Therefore, seed from plantations is probably still the best way to increase the quality and quantity of seed to meet farmers’ demands. Volume 7: Commercial Plantation Forestry 135 Apart from an increase in the quantity of seed by increasing the planted area, it is also important to understand the factors affecting the pollination process. Some previous studies have focused on the reproduction of the genus Aquilaria (Soechartono et al., 2001) but studies on A. crassna, are still limited. Keywords: Moreover, there has been no report on the richness, abundance and efficiency of the species that act as insect pollinators of agarwood in natural forest and plantation. Introduction This study aimed to investigate and compare the role of pollinators in the canopies of natural forest and plantation during the agarwood flowering season. This work mainly focused on the: 1) diversity and abundance of คลังความรู้ดิจิทัลflower visitors;มหาวิทยาลัยเกษตรศาสตร์ 2) behaviour of major insect visitors; and (3) accessibility of flower visitors and their effectiveness as flower pollinators. Materials and Methods Study Sites The study was conducted in two locations in Thailand: a natural forest at Kao Yai National Park; and a private plantation at Khao Saming district. Kao Yai National Park (101°22´E, 14°26´N), the second largest national park in Thailand, covers 216 000 ha in Nakhon Ratchasima, Saraburi, Prachinburi and Nakhon Nayok provinces. This area holds diverse and significant habitat in tropical rainforest ecosystems, containing hill evergreen forest, dry evergreen forest, dry deciduous forest, mixed deciduous forest, secondary forests and grassland (TDRI, 1995). The mean park elevation is 600 m, with the average annual rainfall being 1152.8 mm and the average annual temperature 26.09 °C. According to the official records, the maximum temperature of 33.85 °C and the minimum of 17.15 °C are observed in April and January, respectively (Sangtabtim, 2008). The park contains a wide variety of the generally threatened and endangered fauna and flora of Thailand. In 2005, the Park was designated an UNESCO World Heritage Site under the name ‘Dong Phaya Yen–Khao Yai Forest Complex’ (United Nations, 1992-2007; DNP, 2005). The private plantation, in the Khao Saming district of Trat province in the eastern part of Thailand, covered 12.8 ha, with an average annual rainfall of 1753.0 mm and an average temperature of 28.15 °C. The maximum temperature is in May (33.40 °C), while the minimum is in December 136 FORTROP II: Tropical Forestry Change in a Changing World (22.22 °C). At the time of the study, this plantation contained 15-year-old Nectar Measurement agarwood trees growing on a 2 m x 4 m spacing. Flower Visitors At each habitat, flower visitors were observed on the canopies of six trees of agarwood randomly selected based on their accessibility, flowering performance and isolation. Scaffolding was erected to a height of 4 to 8 m around each tree. A number and species of each visitor was collected with air-flight malaise traps. This method was chosen as this trap was considered effective at capturing Hymenoptera and Diptera (Grazoul, 1997). The flower คลังความรู้ดิจิทัลvisitors were มหาวิทยาลัยเกษตรศาสตร์ collected every week during the flowering period. In addition, Data Analyses visitor collection was supplemented by the use of a sweep net, which was rapidly swept back and forth through the canopy during a 24 hours period (collected for identification in two-hour periods from 16.00 to 16.00 hours). A number of flower visitors and their behaviour were recorded for a 20-minute period each hour. The number of individuals and species, in ten inflorescences (n=10), were recorded in the first 10 minutes, while the visitor behaviour including foraging rate, visitation rate and frequency of flower Results and Discussions visits were then recorded in the second 10 minutes. This observation was performed in each of three years (2006-2008) during March to May, as this Flower Visitors was the dry season with abundant flower blooms. Collected specimens from the trapping and sweeping were labelled and recorded according to their time and location. The visitors were further identified to the species level at the forest entomology laboratory, Faculty of Forestry, Kasetsart University, Thailand and at the Institute of Tropical Agriculture, Kyushu University, Japan. Efficiency Pollination Experiments The efficiency of visitors was conducted on 10-15 inflorescences of each flowering tree species. Unopened flowers in each inflorescence were covered with a flower bag. The bags were then opened at 18:00, once blooming had commenced. The major insect visitors were collected to examine pollen deposits on their body after visiting the flowers. A proportion of the pollen grains deposited on each visitor specimen was counted using a light dissecting stereo microscope. A higher number of pollen grains represented a higher possibility of pollination and a resultant higher efficiency of fruit setting. Volume 7: Commercial Plantation Forestry 137 Nectar Measurement Nectar volumes and concentrations were directly measured at the study site Flower Visitors in the evening period each hour (16:00 to 24:00). This measurement regime commenced as soon as the inflorescence started blooming. Nectar volumes were measured by inserting a 2 μl capillary tube down to the base of each flower (n=90 for sugar of nectar concentration, n=54 for nectar volume).