The timing of snowmelt is a crucial factor determining the phenological schedule a06ng plants, and this causes seasonal change in pollinator activity within the same species. We examined the interspecific competition of alpine plants for bumblebee pollinators through the seasonal change in flowering structures of the alpine plant communities in northern Japan. Interspecific competition for pollinators was classified into exploitation and interference competition. We compared spaces-temporal variations in visit flowering, foraging behaviour (pollen or nectar), flower choice (intra or interspecific movement), caste (queen or worker), and flowering pattern of bee-pollinated plants along the snowmelt gradients.

The exploitation competition was common early in the flowering season when only overwintered queens visited flowers for nectar foraging at very low. In contrast, the interference competition increased with increasing number of flowering species as season progressed, when worker bees moved among plant species for pollen collection. Thus, pollination situation drastically changed as season progressed reflecting the seasonality of bumblebees in alpine ecosystem.