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Download paper Released 2021-11-27

Selection-regulated population dynamics

The vast majority of bird and mammals populations are found to have selection-regulated dynamics, instead of density-regulated growth as assumed in most population dynamic studies.

Fig. 1 Examples of selection-regulated dynamics, with dots being data, green curves the best fitting models, red lines the equilibrium abundances, blue curves n(t+1) n(t) plots, and grey bars the selection induced growth rate accelerations. For details see Witting (2021).

Density dependence and natural selection regulate the dynamics of natural populations, preventing a continued increase in abundance. Selection-regulation, however, was ignored when the theory of population dynamics was developed.

In a release on bioRxiv I analyse the abundance trajectories for more than 1200 populations of birds and mammals to examine whether they are explained by selection-regulated dynamics or by density-regulated growth.

Selection-regulation is essential for 94% of the trajectories based on the best data, explaining 82% of the variance in abundance [462 populations of North American birds with about 50 yearly abundance estimates each]. It is estimated that selection-regulation is 25,000 times more probable than density-regulated growth at the median, with less than 3% of the best population dynamic models having density-regulated growth.

Similar results are obtained for the remaining trajectories covering 111 populations of British birds, 215 populations of Danish birds, and 420 bird and mammal populations in the Global Population Dynamic Database.


  • Witting, L. 2021. Selection-regulated population dynamic in birds and mammals. Preprint at bioRxiv https://dx.doi.org/10.1101/2021.11.27.470201.