m.r.Life ι**=7/3ψ

Selection-accelerated growth

Populations with selection-accelerated growth may decline, or increase, or first decline and then increase in numbers

The simplest form of selection-accelerated growth refers to cases where natural selection is accelerating the population dynamic growth rate at a constant pace. So far, this form of dynamics has been identified as the best population dynamic model for 19 populations of North American birds, 7 populations of British birds, 4 populations of Danish birds, and 16 populations of birds and mammals in the Global Population Dynamic Database.

Fig. 1 Three examples of selection-accelerated growth from Witting (2021). Northern flicker, mourning dove and bald eagle from the North American Breeding Bird Survey (Sauer et al., 2017).

We do not expect the long-term growth of any animal population to be constantly accelerating. Yet, the constant selection-acceleration is a fair approximation when we are unable to identify a change in the acceleration of the growth rate over the time-period of a study. The figure illustrates the three qualitatively difference cases where a population is either declining, or declining and then increasing, or increasing in numbers.

In increasing animal populations, selection-regulation by density dependent interactive competition should eventually appear, slowing down the acceleration of the growth rate, and eventually turn the acceleration into deceleration. Vira and prokaryotes, however, are predicted to evolve without the decelerating selection from a biased resource access by interactive competition (Witting, 2017a,b). This leaves these taxa with stable selection for accelerating growth, as illustrated by the hyperexponential growth curves of Covid-19 (Baruah, 2020; Halley et al., 2021; Pavithran and Sujith, 2022).


  • Baruah, H.K. 2020. Hyper-exponential growth of COVID-19 during resurgence of disease in Russia. Preprint at medRxiv https://dx.doi.org/10.1101/2020.10.26.20219626.
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