Influence of floral traits on visitation patterns in a miniature tropical stingless bee, Tetragonula iridipennis.

Abstract

Miniaturisation can influence the foraging behaviour of flower visitors by shaping their sensory systems, flight capabilities, and their compatibility with floral shapes and structures. For bees, vision is a primary sensory modality, and a reduction in eye size compromises the resolution and sensitivity of vision. In Tetragonula iridipennis, a diminutive tropical stingless bee common in South Asia, we addressed the following questions: (a) Since flight capabilities are correlated with body size, does it largely utilise resources from understorey plants? (b) Does their small body size permit the utilisation of flowers with diverse morphologies? Further, we explored floral colour in relation to bee colour vision by examining if: (c) the distribution of marker points of the community floral spectra (n = 182 species) corresponds with bee photoreceptor sensitivities and (d) the colours of flowers visited or not visited by T. iridipennis form separate clusters in the bee colour space. We found a high degree of resource generalisation, with T. iridipennis visiting ~ 46% of flowering plant species (n = 215). However, three plant species accounted for the highest visitation rates (90%). There was no correlation between plant functional groups and foraging preferences. Floral shape and the interaction between floral area and shape significantly predicted visitation by T. iridipennis. Further studies on other bee species that are sympatric, closely related, and varying in body size will help understand the role of miniaturisation in foraging ecology of pollinators.