Quantifying trade-offs within populations is important in life-history theory. However, most studies focusing on life-history trade-offs focus on two traits and assume trade-offs to be static. Our work provides a framework for understanding covariation among multiple traits and how population density influences the traits. Using detailed individual-based data for Soay sheep, we find density strongly shapes life-history trade-offs and distribution of lifetime reproductive success (LRS). At low density, a trade-off between juvenile survival and growth structures life-history variation whereas at equilibrium density (K), trade-off between reproduction and juvenile survival is the major structuring axes. Contrary to Lomnicki’s prediction, we find the distribution of LRS is highly constrained at K, with mothers of adult sizes contributing the most to reproduction. Our results offer insights into how high density limits diversity of individual life-histories, advance an understanding of dynamic nature of trade-offs and have implications for evolution via density-dependent selection.

Generation time has previously been the focus of comparative life history analyses. Here we examine three metrics: generation time Tc, reproductive dispersion S (the distribution of ages of reproduction), and damping time τ (time to converge to stable (st)age distribution). We use data on 633 species of animals and plants, and perform phylogenetically corrected analyses. First we find that S varies allometrically and isometrically with Tc. As a result, τ varies allometrically with either Tc or S but not both. Second, we find a trade-off between τ and S, so that τ does not vary isometrically with Tc. This trade-off is a novel demographic component to the relationship between τ, Tc and S that is otherwise partly determined by their similarity as biological times. Our results indicate that species at the slow end of the slow-fast continuum take longer to converge to stable distribution than species with fast life-histories.