Waves and synchrony in Epirrita autumnata /Operophtera brumata outbreaks. I. Lagged synchrony: regionally, locally and among species
Article first published online: 29 JAN 2007
Journal of Animal Ecology
Volume 76, Issue 2, pages 258–268, March 2007
How to Cite
TENOW, O., NILSSEN, A. C., BYLUND, H. and HOGSTAD, O. (2007), Waves and synchrony in Epirrita autumnata /Operophtera brumata outbreaks. I. Lagged synchrony: regionally, locally and among species. Journal of Animal Ecology, 76: 258–268. doi: 10.1111/j.1365-2656.2006.01204.x
- Issue published online: 29 JAN 2007
- Article first published online: 29 JAN 2007
- Received 2 October 2006; accepted 23 November 2006
- long-term series;
- spatio-temporal ecology
- 1In 1990–2003, during a complete 10-year outbreak cycle, the synchrony of the birch defoliating outbreaks of the geometrids Epirrita autumnata and Operophtera brumata was studied quantitatively in the northern part of the Fennoscandian mountain chain (the Scandes). Data were supplemented with similar data from 1964 to 1966 and historical information. A 30-year series of field data from one locality in southern Scandes made possible interregional comparisons.
- 2In 1991, outbreaks started in north-eastern Fennoscandia and moved westward like a wave and reached the outer coast of north-western Norway in about 2000. This wave is a new observation. In the same years, a previously documented outbreak wave moved southward along the Scandes.
- 3Outbreak periods have usually occurred around the middle of each decade. Seemingly unrelated population peaks at the decadal shift 2000 were reported from islands at the coast of north-western Norway. They are shown here to have been the final ripples of the east–west wave.
- 4At some localities, O. brumata peaked 2 years after E. autumnata. A lag of 1 or 2 years also occurred at the locality in southern Scandes. This interspecific time lag is a new observation. In accordance with the north–south wave, a time-lag of 1–2 years occurred between the fluctuations of northern and southern E. autumnata and O. brumata populations.
- 5The population peak of E. autumnata occurred 1 year earlier at one locality than at a nearby locality. This pattern and particular altitudinal shifts of the O. brumata population density at these localities repeated in two outbreak periods. This indicates that, for example, local climate may modify outbreak synchrony between nearby localities.
- 6At the same localities, O. brumata peaked first at one altitude and 1 or 2 years later at another altitude. This vertical lag is a new observation.
- 7E. autumnata shows fluctuation traits similar to some other cyclic animals, e.g. the larch budmoth in the European Alps, some European tetraonid birds and the Canadian snow-shoe hare. These similarities (and dissimilarities) in intra- and interspecific synchronies and causes of E. autumnata and O. brumata synchronies, regionally, locally and among the two species are discussed.