Factors limiting the distribution of Acyrthosiphon svalbardicum (Hemiptera: Aphididae) on Spitsbergen

The distribution of the high arctic aphid Acyrthosiphon svalbardicum was found to have a distinct limit in the Kongsfjorden area of Spitsbergen; the probability of site occupancy increased with distance from the fjord mouth and decreased with distance from the shore. Superimposed on this general distribution pattern, sites that cleared of snow early in the polar summer were more likely to be occupied by aphids. The phenology of the aphid was significantly affected by small changes in microclimate over distances of a few metres. The aphid only occurs in the warmer parts of the region, but laboratory cultures were successfully reared on plant material collected from colder regions that the aphid does not presently occupy. These observations suggest that the local distribution of A. svalbardicum is determined by summer thermal conditions. On a smaller scale, within patches where the aphids occurred, densities were higher on flowers and flowering shoots than on non-flowering shoots.