Sister broods in the spruce bark beetle, Ips typographus (L.)

- Recent and historical data on sister broods in Ips typographus are compared.
- Sister broods may considerably increase forest damage by bark beetles.
- Higher number of sister broods can be explained by higher temperature averages.

Establishment of sister broods in the spruce bark beetle, Ips typographus (L.), was investigated at three localities of different elevations (600. 800 and 1100 m a.s.l.) in Sumava Mountains during two consecutive years (2011, 2012). Three sister broods were established at 600 and 800 m a.s.l., in both years, while only two occurred at 1100 m a.s.l. in 2011. A third sister brood at 1100 m a.s.l. was recorded only in 2012. Up to100% of females re-swarmed during first re-emergence. Second and third sister broods were established by 8-90% and 0-22% of females, respectively. The number of established broods is highly correlated with infestation density. Data recorded in this study were compared with similar studies conducted in 1950s by Martinek (1956, 1957, 1961). The influence of climate change and rising temperature averages upon number and intensity of sister broods is discussed as a possible explanation.