Fast environmental change and eco-evolutionary feedbacks can drive regime shifts in ecosystems before tipping points are crossed.

P Catalina Chaparro-Pedraza

doi:10.1098/rspb.2021.1192

Abstract

Anthropogenic environmental changes are altering ecological and evolutionary processes of ecosystems. The possibility that ecosystems can respond abruptly to gradual environmental change when critical thresholds are crossed (i.e. tipping points) and shift to an alternative stable state is a growing concern. Here I show that fast environmental change can trigger regime shifts before environmental stress exceeds a tipping point in evolving ecological systems. The difference in the time scales of coupled ecological and evolutionary processes makes ecosystems sensitive not only to the magnitude of environmental changes, but also to the rate at which changes are imposed. Fast evolutionary change mediated by high trait variation can reduce the sensitivity of ecosystems to the rate of environmental change and prevent the occurrence of rate-induced regime shifts. This suggests that management measures to prevent rate-induced regime shifts should focus on mitigating the effects of environmental change and protecting phenotypic diversity in ecosystems.

Highlights

Environmental change is occurring at unprecedented rates [1], and is triggering both ecological and evolutionary responses in ecosystems [2]
I investigate how ecological, evolutionary and environmental stress dynamics influence regime shifts in ecological systems with alternative stable states (ASSs) in three different model systems corresponding to different ecological scales: a population subjected to an Allee effect; a predator–prey interaction with stage-structured prey; and a shallow lake ecosystem
Once a regime shift occurs, the population collapse is permanent because the system moves from one stable state to another. This is the same behaviour found in the transition region when the two bistability regions overlap (e.g. 1.95 < Emax < 2.2 in figure 3a). — Another region corresponds to an evolving population experiencing gradual increase in environmental stress to a maximum level Emax above the tipping point that marks the collapse in the absence of evolution (TPceco) and below the tipping point that marks the invasion threshold when evolution is enabled by genetic trait variance (TPiecoevo)

Summary

Background

Environmental change is occurring at unprecedented rates [1], and is triggering both ecological and evolutionary responses in ecosystems [2]. One of the most concerning effects of environmental change is that ecosystems do not always respond to gradual change in a smooth manner, but that abrupt transitions occur when environmental conditions cross critical thresholds (i.e. tipping points) [6] These critical transitions, known as regime shifts, have been documented in a variety of ecosystems, including lakes, coral reefs, deserts, woodlands and oceans, and have been attributed to the presence of alternative stable states (ASSs) in ecosystems. There is growing evidence that phenotypic trait changes induced by novel selective pressures can influence ecological processes including population dynamics [12], biotic interactions in communities [13] and ecosystem functions such as nutrient cycling and productivity [14] Given that these ecological processes are central to the biotic feedbacks that maintain ASSs in ecosystems, understanding the effects of environmental change on ecosystems with ASSs requires insight into how ecological, evolutionary and stress dynamics interact. I summarize the findings across the three model systems in the section ‘General patterns in eco-evolutionary systems with ASSs under stress’

Models and results

TPieco 0

Discussion