Interactions between the sexually deceptive orchid Spiculaea ciliata and its wasp pollinator Thynnoturneria sp. (Hymenoptera: Thynninae)

Abstract

Males of the thynnine wasp Thynnoturneria sp. attempt to mate with female decoys in the flowers of the elbow orchid Spiculaea ciliata. Experimentally shifted orchids usually attract male wasps quickly, often within 2 minutes of presentation of the ‘bait’ orchids in appropriate habitat. Although the orchid effectively exploits the scramble competition mating system of the wasp, the insect is not totally at the mercy of the deceptive orchid. Fewer than half of all arriving males contact the column of the orchid flower, as required for orchid pollination. Moreover, the number of deceived visitors falls sharply over a short period and the number of wasp visitors does not rebound with the replacement of one bait orchid by another at that location. These observations suggest that patrolling wasp pollinators can discriminate to some extent between orchid decoys and female wasps, especially by learning to avoid particular locations that are associated with unrewarding flower decoys.