Why climate change will invariably alter selection pressures on phenology

Abstract

The seasonal timing of lifecycle events is closely linked to individual fitness and hence, maladaptation in phenological traits may impact population dynamics. However, few studies have analysed whether and why climate change will alter selection pressures and hence possibly induce maladaptation in phenology. To fill this gap, we here use a theoretical modelling approach. In our models, the phenologies of consumer and resource are ( potentially) environmentally sensitive and depend on two different but correlated environmental variables. Fitness of the consumer depends on the phenological match with the resource. Because we explicitly model the dependence of the phenologies on environmental variables, we can test how differential (heterogeneous) versus equal (homogeneous) rates of change in the environmental variables affect selection on consumer phenology. As expected, under heterogeneous change, phenotypic plasticity is insufficient and thus selection on consumer phenology arises. However, even homogeneous change leads to directional selection on consumer phenology. This is because the consumer reaction norm has historically evolved to be flatter than the resource reaction norm, owing to time lags and imperfect cue reliability. Climate change will therefore lead to increased selection on consumer phenology across a broad range of situations.

Evolutionary traps and range shifts in a rapidly changing world

“…[14]). For many species, shifts in the timing of life-history events in response to environmental change have occurred so quickly that they almost certainly represent cases of behavioural plasticity rather than adaptation [15]. Not all species respond appropriately though, and the potential for traps to emerge in the context of climate change and phenology has recently been highlighted [16].…”

Spatial and temporal heterogeneity in climate change limits species' dispersal capabilities and adaptive potential

“…Ultimately, the unifying feature among these scenarios is that asynchronous regimes are imposing contrasting selection regimes that are difficult to reconcile via either phenotypic plasticity or rapid evolutionary adaptation (Gienapp et al 2014). Plasticity allows populations to track changes in both mean environmental conditions and the variance around that mean under certain circumstances -such as climate change regimes in which warm years are followed by cool years, but there is a uniform trend for warming across seasons and years (Nussey et al 2005).…”

Interactions of climate change and species

“…So, although the two sets of cues will be correlated, the cue used by the consumer (the moth in this case) will always be, to some extent, unreliable. Theoretical work 3 shows that this imperfect cue reliability means consumers will evolve a less temperaturesensitive phenology than will the species at the trophic level they rely on.…”