Circumpolar variation in periodicity and synchrony among gypsy moth populations

1. Previous studies of insect dynamics have detected spatial synchrony in intraspecific population dynamics up to, but not exceeding, 1000 km. Oddly, interspecific synchrony has recently been reported at distances well over 1000 km (at continental and circumpolar scales). While the authors implicated climatic effects as the cause for the apparent large-scale interspecific synchrony, there is no evidence that weather data are synchronized over such great distances. 2. In the present study, intraspecific circumpolar synchrony in the gypsy moth, Lymantria dispar (L.), was tested for among 11 regions across three continents (North America, Europe and Asia). Analyses indicate that most gypsy moth populations around the world tend to oscillate at periodicities between 8 and 12 years. 3. These oscillations were synchronized at distances up to c. 1200 km within continents. There was no evidence for intraspecific synchrony of gypsy moth populations between continents. 4. We suggest that previous reports of interspecific synchrony among insects at scales much greater than 1000 km may suffer from spurious correlations among oscillating populations.