Discussion
The present study revealed that dipteran insects (syrphid and non-syrphid flies) and hymenopteran insects (bumble bees) are the most common flower visitors in the alpine plant communities of Taiwan. On average, 23 and 56% of plant species were predominantly visited by bees and flies, respectively. In comparison with fly-visited plants, floral diversity and flower production of bee-visited plants increased with seasonal progress more apparently, corresponding to the seasonal dynamics of bumble bee workers. These results suggest a consistent linkage between the seasonal dynamics of social bees and the flowering phenology of bee-visited plants in the subtropical alpine ecosystem.