Potential pollen vectors of the mass flowering tree Acacia dealbata, within its natural range in southern Tasmania

Abstract

In Tasmania, Acacia dealbata flowers from July to September when weather conditions are non-conducive to activity by the insects which are generally considered to be major pollinators of the genus. This paper examines the presence and behaviour of insect and bird visitors as potential pollen vectors. Very few insects were observed to visit the flowers. However, several bird species fed on the flower-heads and foraged for small invertebrates inhabiting the blossoms. These feeding behaviours resulted in adhesion of pollen to feathers likely to be transferred from one genet to another as birds moved. During feeding, rosellas were observed to not only ingest flower-heads but the presence of branchlet clip under 57% of A. dealbata trees surveyed is evidence of the widespread occurrence of these species foraging on flowers. However, given the profusion of flowers and the small numbers of birds observed, it is difficult to conclude that birds are wholly responsible for outcross pollination and we discuss the possibility that wind may also be an important pollen vector. Although the floral attributes of A. dealbata are more aligned with insect pollination, we failed to definitively identify any one major pollinator of the species in this environment and suggest that the pollination syndrome may most accurately be described as generalist.