Disconnects between ecological theory and data in phenological mismatch research

Climate change may lead to phenological mismatches, where the timing of critical events between interacting species becomes de-synchronized, with potential negative consequences. Evidence documenting negative impacts on fitness is mixed. The Cushing match-mismatch hypothesis, the most common hypothesis underlying these studies, offers testable assumptions and predictions to determine consequences of phenological mismatch when combined with a pre-climate change baseline. Here, we highlight how improved approaches could rapidly advance mechanistic understanding. We find that currently no study has collected the data required to test this hypothesis well, and 71% of studies fail to define a baseline. Experiments that clearly link timing to fitness and test extremes, integration across approaches, and null models would aid robust predictions of shifts with climate change.