Evol Ecol Res 14: 299-309 (2012)     Full PDF if your library subscribes.

Feedbacks between ecology and evolution: interactions between ΔN and Δp in a life-history model

Curtis M. Lively

Department of Biology, Indiana University, Bloomington, Indiana, USA

Correspondence: C.M. Lively, Department of Biology, Indiana University, Bloomington, IN 47405, USA.
e-mail: clively@indiana.edu


Questions: In a growing population, is there generation-by-generation feedback between population density, the strength of natural selection, and the rate of evolutionary change? What are the overall effects of natural selection and increasing population size on the total change in mean fitness?

Mathematical Methods: Numerical iterations of equations for ∆p and ∆N, coupled with Frank and Slatkin’s method for dissecting Fisher’s fundamental theorem of natural selection.

Assumptions: Large density-regulated populations where genetic drift is minimal. Populations begin at the carrying capacity for homozygotes for one allele, but can increase to a higher carrying capacity as a beneficial life-history allele spreads.

Results: (1) Carrying capacity (K ) increases as a beneficial allele spreads to fixation. (2) The increase in density increases the strength of selection as well as the additive genetic variance for fitness, leading to a more rapid spread of the favoured allele, which further increases the rate of population growth. (3) The negative change in mean fitness due to increasing population size is a time-lagged mirror image of the positive change in mean fitness due to natural selection.

Conclusion: During life-history evolution, generation-by-generation feedback can exist between population density (ecology) and allele-frequency change (evolution).

Keywords: eco-evolutionary feedback, fundamental theorem of natural selection, population ecology, theoretical ecology, theoretical population genetics.

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