We live surrounded by populations. We rely on populations of plants and animals for food; we struggle to control populations of pests and pathogens. The food webs on which we depend on for natural resources are linked populations. We confront the extinction of populations due to a variety of human activities and strive to develop management strategies to preserve biodiversity.

In all these interactions with populations we take into account differences among individuals, due to sex, age, size, developmental stage, physiological condition, etc. That is, populations are always heterogeneous, and we try to account for that heterogeneity in our analyses. … Some differences might be obvious but others remain hidden.  Using sophisticated statistical models, we unraveled the diversity of life history trajectories occurring within an heterogeneous population of an Antarctic seabirds.

We identified three hidden groups, differing substantially in longevity, lifetime reproductive output, and age at first reproduction. Variability in these demographic outcomes is also produced by individual stochasticity, due to random events in the life cycle. Thus we also characterized the relative importance of individual stochasticity versus individual heterogeneity to understand the causes of variation in life histories in populations that contribute to the current debate about the neutrality of life history variation.

The full article, Interacting effects of unobserved heterogeneity and individual stochasticity in the life-history of the Southern fulmar is available in Journal of Animal Ecology.

Stephanie Jenouvrier
Woods Hole Oceanographic Institution