Movement patterns of Cetonia beetles (Scarabaeidae) among flowering Viburnum opulus (Caprifoliaceae)

Abstract

The movement patterns of flower-visiting Cetonia (Coleoptera, Scarabaeidae) were studied in central Sweden over 4 years, providing the first quantitative study of beetle pollination behaviour conducted in a temperate zone. The beetles were marked individually and tracked throughout their visits to Viburnum opulus L. (Caprifoliaceae), a partly beetle-pollinated shrub displaying large umbel-like, creamy-white blossoms. Beetle abundance differed greatly between study years. Of marked beetles observed on V. opulus flowers, an average of 26% returned each year. The beetles performed frequent inter-plant flights, and showed fidelity to particular V. opulus individuals at the study site. Furthermore, they preferred V. opulus to other plants flowering concomitantly and showed considerable constancy in this habit. Movements were mostly between individuals from unshaded locations with high inflorescence and flower number. Normally, the beetles flew on average about 4 times the horizontal nearest-neighbour distance between flowering V. opulus (c. 18 m). From these observations it is concluded that Cetonia beetles are powerful long-distance dispersal agents for V. opulus pollen, perhaps leading to an enhanced gene flow not possible with the plant's other pollinators.