Declining floral color diversity shifts bee color preferences in fragmented habitats

Habitat fragmentation reduces floral color diversity in plant communities, shifting in color preferences of bee pollinators as shown by altered visitation frequency. We conducted a two-year survey of plant-bee interactions on 41 islands and the adjacent mainland habitats in a reservoir island system of eastern China. Reflectance spectra of the flower samples were measured using a portable spectrometer. Results showed that floral color composition was predominantly blue-green and blue, and a reduction in island area significantly decreased floral color diversity. Visitation frequencies to blue-green, ultraviolet-blue, and ultraviolet-green floral colors declined significantly with decreasing island area. Changes in floral color diversity altered bees’ color preferences, significantly impacting total floral visitation frequency. Bees’ color preference for blue-green flowers increased with island area, and floral resources showed no significant effect on visitation frequencies.