PARENT SESSION
Contributed Oral Session 157: Climate Dynamics: Temperature Effects; Modeling
Friday, August 12, 8:00 AM - 11:30 AM, Meeting Room 516 D, Level 5, Palais des congrès de Montréal
Expansion of geographic range in the pine processionary moth caused by increased winter temperatures.
Battisti, Andrea1, Stastny, Michael *,2, Netherer, Sigrid3, Robinet, Christelle4, Schopf, Axel 3, Roques, Alain4, Larsson, Stig5, 1 Department of Environmental Agronomy - Entomology, Legnaro, PD, Italy2 Department of Ecology and Evolutionary Biology, Ithaca, NY, USA3 Department of Forest and Soil Sciences, Vienna, Austria4 Station de Zoologie Forestiere, Ardot Olivet, France5 Department of Entomology, Uppsala, Sweden
ABSTRACT- Global warming is predicted to cause distributional changes in organisms whose geographic ranges are controlled by temperature. We report a recent latitudinal and altitudinal expansion of an important insect pest on pines, the pine processionary moth, Thaumetopoea pityocampa, whose gregarious larvae build nests and feed on foliage in the winter. In north-central France (Paris Basin), its range boundary shifted by 87 km northwards between 1972 and 2004; in northern Italy (Central Alps), an upward shift of 110-230 m in elevation occurred between 1975 and 2004. By experimentally linking winter temperature with feeding activity and survival of T. pityocampa larvae, we attribute the expansion to increased winter survival due to a warming trend over the past three decades. In the laboratory we determined the minimum nest and night air temperatures that are required for larval feeding, and developed a mechanistic model based on this combined feeding threshold. We tested the model in translocation experiments that employed natural temperature gradients as spatial analogues for global warming. In each transect we transferred and monitored colonies of T. pityocampa larvae at sites within zones of historical and recent distribution, and outside the present range. Early-season temperature effects on phenology were evident in delayed development at the more extreme (colder) sites. In the coldest months, our model was supported as feeding activity was progressively reduced with increasing latitude or elevation, corresponding to a lower number of hours when the feeding threshold was reached. Prolonged periods below the feeding threshold occurred at all sites, leading to starvation and mortality. Nonetheless, even the most extreme sites still allowed some feeding, and up to 20% survival of colonies and successful pupation. Given that the present distribution of this oligophagous insect is not constrained by the distribution of its actual or potential host species, we expect that global warming will continue to enhance its survival in previously prohibitive environments, causing further latitudinal and altitudinal expansion. Our work highlights the need to develop temperature-based predictive models for future range shifts of winter-limited species, with potential applications in management.
Key words: climate change, range expansion, insect pest, feeding activity