Birds and mammals have natural selection regulated population dynamics
Statistical estimates of the strength of density and selection regulation covering almost 4,000 bird and mammal populations.
Ecological dynamics is increasingly explained by eco-evolutionary processes, with this study analysing natural selection effects on the population dynamics of birds and mammals. Fitting single-species population dynamic models to 3,369 and 483 timeseries for 900 species of birds and 208 mammals, I find selection-based population dynamic models to be 780 (se:1.3) to 150,000 (se:2) times more probable than models with no selection. Selection is essential in 79% to 92% of AIC selected models, explaining 80% of the population dynamics variance, with median selection regulation being 1.2 (se:0.11) times stronger than density regulation. The estimated dynamics is cyclic with median damping ratios of 0.12 (se:0.0071) and 0.062 (se:0.021) for birds and mammals, and median population periods of 8.3 (se:0.99) and 7.2 (se:0.85) generations for stable cycles with damping ratios around zero. These results resolve several enigmas of population cycles, highlighting the importance of integrating natural selection into population dynamics.