Spatial Distribution of Flower Visiting Beetles in Pasoh Forest Reserve and Its Study Technique

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To recognize how to maintain sustainable biodiversity in tropical forests, the spatial distributions of flower-visiting beetles were investigated using flower fragrance traps in the Pasoh Forest Reserve (Pasoh FR). 1) The vertical distribution of flower-visiting beetles was investigated using the balloon system and treetowers. Most flower-visiting beetles (Scarabaeidae) were trapped from 10 m to 25 m above ground, indicating that they are active in the continuous middle layer of the canopy, where most trees and climbers bear flowers. Mecinonota regia sumatrana were, however, distributed in the relatively low layer, while Dasyvalgus dohlni was distributed in the upper part of the canopy. 2) The horizontal distribution of flowervisiting beetles was investigated using flower fragrance traps in the Pasoh FR to analyze fragmentation and edge effects. Since this forest is surrounded by oil palm plantations and rubber plantations, it remains as an island of forest within them. The number of Dasyvalgus, one of the main flower-visiting groups, was significantly greater in the primary forest area than in the regenerating area whilst Mecinonota showed no difference. The community structure of scarabaeid beetles was different between the primary forest area and the regenerating forest area. However, difference of beetle fauna between the primary forest area and the regenerating forest area might be more affected by selective logging ca. 40 years ago than the fragmentation or edge effects. This suggests that the effects of selective logging on the beetle fauna still remain even after more than 40 years. Thus, both the observations on vertical and horizontal distributions of flower-visiting beetles imply that management of tropical rain forests should aim to conserve the complex spatial structure of primary forests. 3) Comparison among the trapping systems for canopy fauna in tropical forests were discussed. Balloon trap system and tree-tower with fragrance traps of linalool, eugenol and methyl benzoate were effective for collection of flower-visiting insects on tropical rain forest canopy. The effectiveness of the balloon trap system and tower systems were not different.