Flexibility of the spruce budworm - parasitoid food web

Abstract

The reduction in diversity is reducing the capacity of food webs to respond to variability. Two potentially important food web mechanisms are flexible food web structure and spatiotemporal coupling. To date, little research has examined flexibility and spatiotemporal coupling at the community scale. The large variation in spruce budworm densities every 35 years likely causes the community of parasitoids to shift from spruce budworm on balsam fir (a softwood) to other caterpillars on hardwood trees. We examined whether the parasitoid community flexibly responded to the changing relative abundances of spruce budworm and other caterpillars and exhibited spatiotemporal coupling of balsam fir and hardwoods. We found that the parasitoid community tracked the changing relative abundances of spruce budworm and other caterpillars and spatiotemporally coupled balsam fir and hardwoods. Community-level flexibility and spatiotemporal coupling could mute large oscillations. Therefore, maintaining hardwood tree diversity could similarly mute the large spruce budworm density fluctuations.