The mechanisms of phenology: the patterns and processes of phenological shifts

Abstract

Species across a wide range of taxa and habitats are shifting phenological events in response to climate change. While advances are common, shifts vary in magnitude and direction within and among species, and the basis for this variation is relatively unknown. We examine previously suggested patterns of variation in phenological shifts in order to understand the cue–response mechanisms that underlie phenological change. Here, we review what is known about the mechanistic basis for nine factors proposed to predict phenological change (latitude, elevation, habitat type, trophic level, migratory strategy, ecological specialization, species’ seasonality, thermoregulatory mode, and generation time). We find that many studies either do not identify a specific underlying mechanism or do not evaluate alternative mechanistic hypotheses, limiting the ability of scientists to predict future responses to global change with accuracy. We present a conceptual framework that emphasizes a critical distinction between environmental (cue‐driven) and organismal (response‐driven) mechanisms causing variation in phenological shifts and discuss how this distinction can reduce confusion in the field and improve predictions of future phenological change.

Grasshopper phenological responses to climate gradients, variability, and change

“…, Chmura et al. ), but contrary to initial findings for our system based on adulthood (Nufio et al. ).…”

“…These variable responses reflect the important role that environmental exposure, including non‐uniform warming and interannual variability, plays in influencing the phenological advancement of insects and other ectotherms (Chmura et al. ). While the time of adulthood is delayed with elevation, spring and summer warming at higher elevations has reduced the steepness of this expected delay, as it has in other systems (Vitasse et al.…”

“…Many studies have compared phenological responses across environmental gradients (reviewed by Chmura et al 2018), and some have examined gradients of organismal sensitivity (at the species or population level; Thackeray et al 2016), but few have explored the role of shifting developmental trajectories (Yang and Rudolf 2010). As metrics for adult phenology (e.g., first appearance, percentile individual, peak abundance) are subject to detection biases and can fail to capture the nuances of phenological shifts (Diez et al 2012, CaraDonna et al 2014, Brown et al 2016, Inouye et al 2019, examining developmental progression provides detailed insight into the drivers influencing developmental rates and ultimately the variability associated with the timing to adulthood.…”

“…Organismal sensitivity may be shaped by adaptive phenotypes such as thermal specialization (Buckley et al 2013b, Buckley and, which may produce more pronounced phenological responses (Vitasse et al 2009, Chmura et al 2018. We expect that shortwinged and flightless species will exhibit more genetic differentiation and thus a greater potential for local adaptation (Knowles 2000).…”

Crowd‐sourced data reveal social–ecological mismatches in phenology driven by climate

“…Phenological mismatch refers to differences in the timing of life-history events between interacting species that affect their performance (Chmura et al 2019). Changes to the environment, including climate change, can shift the seasonal timing and temporal overlap of these interactions (Kharouba et al 2018).…”