When the going gets tough, the tough get going: effect of extreme climate on an Antarctic seabird’s life history

Abstract

1AbstractIndividuals differ in many ways. Most produce few offspring; a handful produce many. Some die early; others live to old age. It is tempting to attribute these differences in out-comes to differences in individual traits, and thus in the demographic rates experienced. However, there is more to individual variation than meets the eye of the biologist. Even among individuals sharing identical traits, life history outcomes will vary due to individual stochasticity, i.e., to chance. Quantifying the contributions of heterogeneity and chance is essential to understanding natural variability. Inter-individual differences vary across environmental conditions. Heterogeneity and stochasticity depend on environmental conditions. We show that favorable conditions increase the contributions of individual stochasticity, and reduce the contributions of heterogeneity, to variance in demographic outcomes in a seabird population. The opposite is true under poor conditions. This result has important consequence for understanding the ecology and evolution of life history strategies.

Demystifying individual heterogeneity

“…Individual stochasticity could be modelled in a population of identical individuals, while models of dynamic condition must incorporate among‐individual variation in potential vital rates. Recent works have made a similar distinction by treating individual stochasticity and “dynamic heterogeneity” as separate processes (Coste & Pavard, 2020; van Daalen & Caswell, 2020; Hartemink & Caswell, 2018; Jenouvrier et al, 2019).…”

“…This approach follows previous definitions in the field (e.g. Vindenes et al, 2008;Bonnet & Postma 2016;Cressler et al, 2017;Jenouvrier et al, 2019), but contrasts with broader definitions that allow individual heterogeneity to refer to any amongindividual variation (e.g. Hamel et al, 2018;Jolles et al, 2020).…”

“…Individual heterogeneity refers to variation among individuals in their potential vital rates, and it is important to distinguish this variation from individual stochasticity. Individual stochasticity refers to the differences among individual realisations of the same underlying, potential, vital rate (Box 1; Figure 1; see also Caswell, 2009; Hartemink & Caswell, 2018; Jenouvrier et al, 2019). The resulting variation may resemble that which is produced by dynamic condition because both processes allow individual vital rates to take on new values at any time.…”

The relative contribution of individual quality and changing climate as drivers of lifetime reproductive success in a short-lived avian species

“…Part of the uncertainty may arise from the context of events. For example, in southern fulmars ( Fulmarus glacialoides ), when conditions were favorable, environmental stochasticity influenced LRS, but during poor conditions, heterogeneity in individual traits explained greater variation in LRS 25 . Additionally, the majority of studies focus on long-lived species, whereas short-lived species that breed only once or twice in their lifetime may be less able to contend with fluctuating or extreme environmental conditions.…”

The Contributions of Maternal Age Heterogeneity to Variance in Lifetime Reproductive Output

“…From Figure 4, it is clear that "poor" environments are not all equivalent. Several recent studies have reported an increase in the importance of heterogeneity when environments become poor, where poor environments result in a decrease in (some of) the vital rates (e.g., Tavecchia et al, 2005;Barbraud and Weimerskirch, 2005;Jenouvrier et al, 2019). This could be due to the fact that individuals are more likely to allocate resources away from reproduction to maintaining their survival when they encounter very poor environments.…”