Individual Heterogeneity in Animal’s Life Histories

Individual variation is not only a building block for evolution, but it can also profoundly affect ecological responses: the average performance of all individuals in a population is typically different from the performance of a population of average individuals. In ecology, identifying life-history strategies is traditionally done by quantifying differences among individuals in observed traits (age, sex, size). Furthermore, comparative analyses have shown that there is a slow-fast continuum of life-history strategies across species. However, we may have only scratched the surface, as there is more to individual variation than meets the eye. Currently, we still have a limited understanding of how much unobserved heterogeneity occurs in populations, which patterns they exhibit, whether environmental variability affects these patterns, and thereby what their ecological implications are. Excitingly, recently important analytical advances have been made to quantify unobserved heterogeneity in demographic rates and how different demographic rates covary within a population. An outstanding question that remains to be answered is how diverse life-history strategies exists within species in general. To answer this, we will jointly analyse longitudinal data of a large set of species located along the slow-fast continuum. Accounting for both observed and unobserved individual heterogeneity using a common methodological framework we aim to unravel systematic new patterns of life-histories within species that will transform or complement the current paradigm of life-histories.