Synchronization of Outbreaks

• Defoliation caused by the gypsy moth, Lymantria dispar L., in Massachusetts in 1971-86. From Liebhold and Elkinton (1989; Forest Sci. 35: 557-568).
• Outbreak of the mountain pine beetle, Dendroctonus ponderosae Hopk., in lodgepole pine forests of Glacier National Park. From McGregor et al. (1983; USDA Report 83-16).

• Direct weather effect (this is a good explanation for gradient species)
• Migration from outbreak area triggers an outbreak in adjacent areas (e.g., bark beetles)
• Weather synchronizes population oscillations = Moran's effect (gypsy moth?)