When is population structure important? Integrating transient dynamics and life-history theory

James Inman Cant , Christina Maria Hernandez, David Koons, David J Hodgson, Man Qi, Andrew Hector, Iain Stott, Rob Salguero-Gomez

Population dynamics are governed not just by the vital rates of the members of a population, but also by population structure (i.e., the distribution of individuals along species life cycles). A conventional focus of population biology and viability analyses has been to determine the influence of vital rates on long-term predictions such as stable population growth rates. With increasing appreciation of the importance of transient dynamics caused by non-stable population structures, we challenge this conventional focus and encourage the integration of population structure in assessments of population performance and resilience. To underscore the importance of population structure to realised population performance, we apply a transient Life Table Response Experiment framework to 268 comparisons of observed variation in population performance across 56 plant species over differing time periods, locations, and/or experimental treatments. We emphasise how changes in population structure are as consequential in determining realised demographic performance as shifts in survival and fecundity, particularly in populations characterised by ‘faster’ life-histories and a more limited capacity for contributing offspring throughout their lifespan. Overall, quantifying how population structure affects realised population dynamics can reveal key mechanistic insights for enhancing our management of natural systems and our understanding of life-history variation.