Climate warming has caused the seasonal timing of many components of ecological food chains to advance (Thackeray et al. 2010, 2016). Differential shifts lead to phenological asynchrony, often referred to as trophic mismatch when it is detrimental for consumers (Cushing 1990). In the context of trophic interactions, it has been suggested that consumers will shift their phenology to adapt to shifts in the availability of their food source (Visser and Both 2005), but they rarely do so in practice (Thackeray et al. 2016; Kharouba et al. 2018). Whether such unequal shifts are detrimental or not is unresolved (Johansson and Jonzén 2012; Reed et al. 2013a; Samplonius et al. 2016; Radchuk et al. 2019; Visser and Gienapp 2019). At present there has been no consistent analysis of the links between temperature change, phenological asynchrony, and individual-to-population level impacts across taxa, trophic levels and biomes at a global scale. Instead, many of our insights into mismatch and its impacts stem from a handful of independent single-system studies, varying greatly in their conceptual basis and methodological approach. Here, we propose five criteria that all need to be met to demonstrate that temperature-mediated trophic mismatch poses a growing risk to consumers. These criteria are: 1) an ephemeral resource contributes a large proportion of the consumer’s diet; 2) asynchrony between phenology of consumer and resource is increasing over time; 3) interannual variation in asynchrony is driven by interannual variation in temperature; 4) asynchrony reduces consumer fitness, 5) mismatch impacts negatively on consumer population size or growth. We conduct a literature review of 109 papers studying 132 taxa, and find that for most taxa only two of the five criteria are met. Moreover, all five criteria are only assessed for two taxa. The most commonly-tested criteria are 1 and 2, and few studies further examined evidence for criteria 4 or 5. Furthermore, effects of mismatch are heavily skewed towards juvenile stages rather than adults. Crucially, nearly every study was conducted in Europe or North America, and most studies were on terrestrial secondary consumers. We thus lack a robust evidence base from which to draw general conclusions about the risk that climate-mediated trophic mismatch may pose to populations worldwide.
No evidence for fitness signatures consistent with increasing trophic mismatch over 30 years in a population of European shag
Phalacrocorax aristotelis