Uncertainty propagation in matrix population models: gaps, importance, and guidelines
O_LIMatrix population models (MPMs), which describe the demographic behaviour of a population based on age or stage through discrete time, are popular in ecology, evolutionary biology, and conservation biology. MPMs provide a tool for guiding management decisions and can give insight into life history trade-offs, patterns of senescence, transient dynamics, and population trajectories. These models are parameterised with estimates of vital rates (e.g. survival and reproduction) and can have multiple layers of underlying statistical analyses, all of which introduce uncertainty. For accurate and transparent results, this uncertainty should be propagated through to quantities derived from the MPMs. However, full propagation is not always achieved, leading to omitted uncertainty, and negative consequences for the reliability of inferences drawn. C_LIO_LIWe summarised the state-of-the-art regarding vital rate uncertainty reporting and propagation, by reviewing papers using MPMs from 2010-2019. We then used reported uncertainties as the basis for a simulation study to explore the impact of uncertainty omission on inferences drawn from the analysis of MPMs. We simulated four scenarios of vital rate propagation and evaluated their impact on population growth rate estimates. C_LIO_LIAlthough around 78% of MPM papers report some kind of uncertainty in their findings, only half of those report uncertainty in all aspects. Additionally, only 31% of papers fully propagate uncertainty through to derived quantities. Our simulations demonstrate that, even under a median uncertainty level, incomplete propagation introduces bias. Omitting uncertainty may substantially alter conclusions, particularly for results showing small changes in population size. Biased conclusions were most common when uncertainty in the most influential vital rates for population growth were omitted. C_LIO_LIWe suggest comprehensive guidelines for reporting and propagating uncertainty in MPMs. Standardising methods and reporting will increase the reliability of MPMs and enhance the comparability of different models. These guidelines will improve the accuracy, transparency, and reliability of population projections, increasing our confidence in results that can inform conservation efforts, ultimately contributing to biodiversity preservation. C_LI