The impact of phenological mismatch varies across woodland food-web interactions

Abstract

Climate warming is altering the timing of seasonal events across ecosystems, impacting the temporal synchrony of interactions among species1,2. For trophic interactions, the match-mismatch hypothesis predicts that when consumers become phenologically asynchronous with key ephemeral resources their fitness will decline3-5. Most studies of mismatch focus on single resource-consumer species pairs, and implicitly assume trophic specialisation. However, many consumers exploit more than one resource species, giving rise to several mechanisms whereby the negative impacts of mismatch on individuals and populations could be buffered6. Here we experimentally manipulate phenological asynchrony across 48 plant-caterpillar interactions in a spring woodland food-web system and assay caterpillar performance. As asynchrony increases, we find strong evidence for a decline in survival that generalises across host-caterpillar interactions, whereas caterpillar growth and development are largely unaffected. We also show that focus in the literature on a single model interaction (Oak-Winter Moth)7,8 has likely overestimated the general impact asynchrony in this system. The strength of the effect of mismatch varies markedly among host-plants, caterpillars, and their interactions--with a small number of interactions showing little or no decline in consumer performance despite substantial asynchrony. Our results demonstrate that the fitness consequences of phenological mismatch are widespread but interaction-specific, revealing substantial heterogeneity in how trophic interactions are expected to respond to climate-driven shifts in seasonal timing. This variation in response could allow resource diversity and resource switching to buffer consumer guilds against the phenological impacts of ongoing climate change, stabilising the abundance of caterpillars for higher trophic levels.