Temperature-dependent reproduction of the spruce bark beetle Ips typographus, and analysis of the potential population growth

Authors


B. Wermelinger, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), CH-8903 Birmensdorf, Switzerland. E-mail: beat.wermelinger@wsl.ch

Summary

1. The spruce bark beetle Ips typographus (L.) is one of the most important forest pests in Central Europe, but despite this the effects of temperature on life history and population growth are largely unknown. This study examines the effects of temperature on reproduction and intrinsic demographic statistics.

2. Laboratory experiments on oviposition were carried out at six temperatures in the range 12–33 °C, using the so-called sandwich rearing technique for bark beetles.

3. A linear relationship between oviposition rates and temperatures in the range 15–25 °C was used to estimate the lower temperature threshold for oviposition as 11.4 °C. With a nonlinear model fitted to the data across the whole range of experimental temperatures, the lower and upper limiting temperatures and optimum temperature were found to be 7.9, 33.7, and 28.9 °C, respectively. A model for daily oviposition rate was fitted, which describes the pattern of oviposition over the entire oviposition period.

4. The analysis of life tables, combining developmental rates, reproduction, mortality, and sex ratio, suggests maximum population growth (rm) at near 30 °C.

5. After generating a first brood, spruce bark beetles often re-emerge from the tree and produce other sister broods. The effects of temperature and number of sister broods on demography were evaluated using age-specific life-table analyses. It is hypothesized that sister broods play an important role in regions where I. typographus is monovoltine, but have only moderate significance where this species has more than one generation per season.

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