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.

Methods
We located papers relating phenological data from trophic interactions to fitness and/or performance of the consumer and/or the resource by conducting keyword searches in ISI Web of Science published up to June 2017. Keywords included phenolog* AND mismatch* OR synchron* AND interact* AND (fitness* OR performance*). If more than one measure of phenology was included, we chose the one used by the authors to calculate mismatch and examine its impact on performance. Our final review included 42 studies with 45 pair-wise species interactions (3 studies had 2 interactions). Based on the type of data collected for the consumer and resource, we classified studies as life history (i.e. one that collected data at the individual level) or one that collected data at the population or community (i.e., across species). To determine whether studies had the potential to define pre-climate change baselines, we measured the study’s time span and years of data based on the years where phenology data was available for both the consumer and resource, and consumer performance data was available.