Rapid phenological change differs across four trophic levels over 15 years

The success of consumers often depends on synchronizing with their resources; however, recent climate change has affected the phenology of many species, resulting in mismatches and leading to community-wide changes. Field studies chronicling both the dynamics and behavior of four trophic levels seldom run for more than a few years, thereby bringing into question the longer term trajectories of these phenological shifts at multiple levels. Do these shifts between trophic levels remain constant over time, or do they continue to move apart? To address these questions, in 2004, I initiated a long-term study of the phenological relationships of two ferns, a host caterpillar (and its moth), its principal primary parasitoid wasp, and hyperparasitoid wasp. The study involves only a few species at each level, but they make up nearly all the members of the community. Ferns emerged progressively earlier in the spring, at rates exceeding one day per year, while moths eclosed roughly 0.6 days earlier per year, the primary parasitoid at 0.8 days earlier per year, and the hyperparasitoid fluctuated widely. Each of these changes fostered significant mismatches. Year-to-year changes of the moth and primary parasitoid varied much more than those of the ferns. In each instance, dates of last eclosions moved earlier more rapidly than did early eclosion dates, truncating their seasons. The extremely rapid, though variable, changes in phenology of the various trophic levels follow the unprecedentedly rapid temperature increase of the immediately adjacent Gulf of Maine.