Evolutionary tracking is determined by differential selection on demographic rates and density dependence

Abstract

Recent ecological forecasts predict that ~25% of species worldwide will go extinct by 2050. However, these estimates are primarily based on environmental changes alone and fail to incorporate important biological mechanisms such as genetic adaptation via evolution. Thus, environmental change can affect population dynamics in ways that classical frameworks can neither describe nor predict. Furthermore, often due to a lack of data, forecasting models commonly describe changes in population demography by summarizing changes in fecundity and survival concurrently with the intrinsic growth rate (r). This has been shown to be an oversimplification as the environment may impose selective pressure on specific demographic rates (birth and death) rather than directly on r (the difference between the birth and death rates). This differential pressure may alter population response to density, in each demographic rate, further diluting the information combined to produce r. Thus, when we consider the potential for persistence via adaptive evolution, populations with the same r can have different abilities to persist amidst environmental change. Therefore, we cannot adequately forecast population response to climate change without accounting for demography and selection on density dependence. Using a continuous‐time Markov chain model to describe the stochastic dynamics of the logistic model of population growth and allow for trait evolution via mutations arising during birth events, we find persistence via evolutionary tracking more likely when environmental change alters birth rather than the death rate. Furthermore, species that evolve responses to changes in the strength of density dependence due to environmental change are less vulnerable to extinction than species that undergo selection independent of population density. By incorporating these key demographic considerations into our predictive models, we can better understand how species will respond to climate change.

Prediction of the minimum effective size of a population viable in the long term

“…Other factors such as adaptation to environmental changes and population regulation by density-dependence are also worthy of study given their impact on the risk of extinction (Vinton and Vasseur 2020). For instance, Brook et al (2006) found smaller MVPs under three (negative) density-dependence models than under two density-independent models, the MVPs for the latter being around two orders of magnitude larger than those for the former.…”

Plasticity’s role in adaptive evolution depends on environmental change components

“…Impact of environmental variation and temporal autocorrelation on underlying genetics Moderate environmental variation can optimise selection, and ultimately evolutionary tracking [45,46] (but see [2]). In contrast, the ability of populations to evolutionarily track a shifting adaptive peak can increase with greater temporal autocorrelation [25].…”

“…It is usually assumed that a more variable environment is detrimental for populations. However, recent syntheses show that the effect of environmental variability can have both positive and negative effects on population growth rates [2,59]. For example, disparities in population size responses to environmental variability are influenced by differences in the magnitude of density dependence [60].…”

“…This decrease in the benefit of plasticity is in part due to the lack of predictability in the temporal environment. Moreover, in a highly variable environment with a stationary mean, evolution may be nonadaptive [2,88], and thus plasticity may allow the genotypic mean to remain near the environmental mean amidst the environmental variability.…”

“…Understanding, quantifying, and predicting the ability of organisms to adapt to changing environments is at the core of ecoevolutionary research [1][2][3][4]. In the face of unprecedented environmental change (see Glossary), natural populations, especially those with limited mobility/dispersal, can avoid extinction via phenotypic plasticity and/or adaptive evolution [4].…”