Evidence for a food-deceptive pollination system using Hylaeus bees in Caladenia hildae (Orchidaceae)

Abstract

Numerous orchid species are pollinated by food deception, where rewardless flowers attract foraging pollinators through the mimicry of other flowers or the use of non-specific floral signals. Here we investigate the pollination of Caladenia hildae, a member of a diverse Australian genus containing species pollinated by sexual deception, and species pollinated by food foraging pollinators. Despite eight bee species occurring at the main study site, only food foraging bees of a single species of Hylaeus (Colletidae) were observed to remove and deposit pollen of C. hildae. Spectral reflectance of C. hildae flowers differed from co-flowering rewarding species in terms of both the wavelengths of light reflected, and the pattern of colouration. As such, there was no evidence that C. hildae uses a pollination strategy based on floral mimicry. However, the attraction of only a single bee species at this site suggests that C. hildae may use a deceptive strategy that exploits sensory biases or behaviours that differ between Hylaeus sp. and the remainder of the bee community. While Hylaeus have been recorded visiting orchid flowers in several parts of the world, C. hildae may represent the first documented case of an orchid species specialised on pollination by Hylaeus bees.