Biology subjects

ZUO, W.

Publications and source records attributed to ZUO, W..

2 recordsLinked to original sources

bioRxiv2024

Density dependence shapes life-history trade-offs in a food limited ungulate population

Quantifying trade-offs within populations is an important goal in life-history and evolutionary theory. However, most studies focusing on life-history variation assume trade-offs to be static. In this paper, we provide a framework for understanding life-history variation at different densities while enabling us to reveal trade-offs that are often masked due to individual heterogeneity. We use published individual-based data from a population of Soay sheep and find density dependence strongly shapes life-history trade-offs and the distribution of lifetime reproductive success. We find trade-offs between juvenile survival and growth structures life-history variation for Soay sheep at all densities, but the intensity of the trade-offs increases with population density. At carrying capacity (K), a new trade-off appears between reproduction and juvenile survival. In addition, we find the distribution of LRS to be highly constrained at K, with mothers of prime adult sizes ([~] 25kg) contributing the most to reproduction. We also find the effects of density-dependence on demographic measures such as net reproductive rate, stable size distribution, and average vital rate functions. Our results suggest high density limits the diversity of individual life history strategies and has implications for better understanding the evolution of reproductive tactics via density-dependent selection and management of ungulates in food limited environments.

ecology↗

bioRxiv2023

Sensitivity and uncertainty in the Lee-Carter mortality model

BACKGROUNDThe Lee-Carter model (LC) is widely used in research and applications for forecasting age specific mortality, and typically performs well regardless of the uncertainty and often the limited quality of mortality data. OBJECTIVEWhy dose LC perform well regardless of the uncertainty and the limited data quality? METHODSWe analyze the robustness of LC using sensitivity analyses based on matrix perturbation theory, coupled with simulations that examine the effect of unavoidable randomness in mortality data. The combined effects of sensitivity and uncertainty determine the robustness of LC. RESULTSWe find that the sensitivity of LC and the uncertainty of death rates both have nonuniform patterns across ages and years. The sensitivities are small in general, with largest sensitivities at both ends of the period. The uncertainty of death rates are high in young ages (5-19) and old ages (90+) with rising in young ages but dropping in old ages. CONCLUSIONSThe sensitivity and uncertainty analyses indicate that the randomness hardly interrupts the prediction of LC. The divergence of long term prediction in LC is likely due to structural changes in the age-year specific mortality, which is associated with the development of public health policy, medical innovations and chronic disasters. CONTRIBUTIONOur results reveal that LC is robust against random perturbation and sudden short term changes.

ecology↗