Micrometeorological impacts on insect activity and plant reproductive success in an alpine environment, Swedish Lapland

The effects of weather on the flight and flower-visiting activity of bumblebees and butterflies were studied at a subarctic-alpine site in northern Swedish Lapland. The study focused on the insects' role as potential pollinators and the effect of bumblebee flight and foraging activity on plant reproductive success. The activity rates of both bumblebees and butterflies were significantly correlated with ambient air temperature and solar radiation, and as a consequence, both bumblebees and butterflies exhibited a regular diurnal activity pattern. The butterflies' activity was more constrained by low temperature and solar radiation then the bumblebees' activity, and small worker bees were more affected by the weather than the larger queens. Only 1% of the butterflies observed were visiting flowers, as compared to 69% of the bumblebees. Thus, butterflies seem to be less important pollinators for the alpine plant community than bumblebees. Short-term micrometeorological impact on the reproduction of two bumblebee-pollinated plant species, Bartsia alpina and Diapensia lapponica, was also studied. In both species, reproductive success, measured as seed production, was significantly reduced during a spell of cold weather in comparison to a warmer period.