Distinguishing within- from between-individual effects: How to use the within-individual centering method for quadratic patterns

Fay, Rémi; Martin, Julien G. A.; Plard, Floriane

doi:10.1101/2020.05.25.114421

Cited by 2 publications

(2 citation statements)

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“…14 To separate the selection hypothesis from the constraint or restraint hypotheses, we applied two different approaches. First, based on an adaptation of the within-individual centering method (van de Pol and Wright 2009) and quadratic effects (Fay et al 2020), we separated within-and among-individual age-related changes in breeding performances. Briefly, within-individual centering was performed by subtracting an individual's mean age from its age in different years.…”

Section: Within-versus Among-individual Changes In Breeding Performancesmentioning

confidence: 99%

“…Only individuals known during their entire lifetime were included, i.e.individuals that had not been seen at the colony after 2016, corresponding to 301 penguins, and not including those 172 penguins that were still alive at the end of the study period. The same procedure was conducted using the squared age variable (age² -mean (age²)) (more details in Fay et al, 2020). Again, this model was run separately on males and females.…”

Section: Within-versus Among-individual Changes In Breeding Performancesmentioning

confidence: 99%

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Age‐related breeding success in little penguins: a result of selection and ontogenetic changes in foraging and phenology

Saraux

Chiaradia

2021

Ecological Monographs

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Reproductive performance typically improves with age, reaching a plateau at middle age and subsequently declining in older age classes (senescing individuals). Three potential non-exclusive mechanisms can explain the improvement in reproductive performance with age: (1) selection (poor quality individuals are removed from the population with increasing age), ( 2) constraint (individual efficiency increases through experience), and (3) restraint (reproductive investment increases with age as the residual reproductive value decreases). While all three mechanisms received strong empirical support, few studies have aimed at teasing apart those hypotheses and understanding their underlying functioning. In little penguins (Eudyptula minor), we used a 19-yr longitudinal dataset on breeding and foraging of more than 450 individuals to investigate the effect of age on breeding success. We separated within-individual from among-individual age effects using state-of-the-art statistical methods (within-subject centering and population change decomposition). We then assessed whether within-individual changes in breeding resulted from ontogenetic changes in foraging performances, breeding phenology or access to mates and nest sites. Fidelity and assortative pairing explained the high correlation in male and female ages within a pair. Breeding performances followed a typical bell-shaped curve with performance increasing up to 8 yr old, before reaching a plateau and subsequently declining after age 16. Both selection and within-individual processes occurred, although within-individual changes dominated differences in age-dependent breeding success. The selective appearance had almost no effect (apart from ages 2-3), and selective disappearance mostly affected changes at old ages (above 16), although they were also responsible for the slight increase in reproductive performances from ages 5-8. Focusing on within-individual changes, birds exhibited higher performances at middle ages, with birds foraging better, laying earlier and changing partner and nest less often. Their reproductive investment did not vary with age for females and slightly decreased for males. This supports the constraint hypothesis but not the restraint one. Finally, the increase in breeding performances at young ages was explained by the age-related increase in foraging performances during chick-rearing and advancement of laying. In contrast, reproductive senescence was defined by a general decrease in bird performances.

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Section: Within-versus Among-individual Changes In Breeding Performancesmentioning

confidence: 99%

Section: Within-versus Among-individual Changes In Breeding Performancesmentioning

confidence: 99%

Age‐related breeding success in little penguins: a result of selection and ontogenetic changes in foraging and phenology

Saraux

Chiaradia

2021

Ecological Monographs

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Age-specific reproduction in female pied flycatchers: evidence for asynchronous aging

Fay

Ravussin²,

Arrigo³

et al. 2021

Oecologia

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Age-related variation in reproductive performance is central for the understanding of population dynamics and evolutionary processes. Our understanding of age trajectories in vital rates has long been limited by the lack of distinction between patterns occurring within- and among-individuals, and by the lack of comparative studies of age trajectories among traits. Thus, it is poorly understood how sets of demographic traits change within individuals according to their age. Based on 40 years of monitoring, we investigated age-related variation in five reproductive traits in female pied flycatchers (Ficedula hypoleuca) including laying date, clutch size, brood size, nest success (probability that a nest produces at least one chick) and egg success of successful nests (proportion of eggs resulting in a chick). We disentangled within- from among-individual processes and assessed the relative contribution of within-individual age-specific changes and selective appearance and disappearance. Finally, we compared the aging pattern among these five reproductive traits. We found strong evidence for age-specific performance including both early-life improvement and late-life decline in all reproductive traits but the egg success. Furthermore, the aging patterns varied substantially among reproductive traits both for the age of peak performance and for the rates of early-life improvement and late-life decline. The results show that age trajectories observed at the population level (cross-sectional analysis) may substantially differ from those occurring at the individual level and illustrate the complexity of variation in aging patterns across traits.

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Distinguishing within- from between-individual effects: How to use the within-individual centering method for quadratic patterns

Cited by 2 publications

References 52 publications

Age‐related breeding success in little penguins: a result of selection and ontogenetic changes in foraging and phenology

Age‐related breeding success in little penguins: a result of selection and ontogenetic changes in foraging and phenology

Age-specific reproduction in female pied flycatchers: evidence for asynchronous aging

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