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From early-life to senescence: individual heterogeneity in a long-lived seabird
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Edité par CCSD ; Ecological Society of America -
International audience. Although population studies have long assumed that all individuals of a givensex and age are identical, ignoring among-individual differences may strongly bias our perceptionof eco-evolutionary processes. Individual heterogeneity, often referred to as individualquality, has received increasing research attention in the last decades. However, there are stillsubstantial gaps in our current knowledge. For example, there is little information on how individualheterogeneity influences various life-history traits simultaneously, and studies describingindividual heterogeneity in wild populations are generally not able to jointly identify possiblesources of this variation. Here, based on a mark–recapture data set of 9,685 known-agedWandering Albatrosses (Diomedea exulans), we investigated the existence of individual qualityover the entire life cycle of this species, from early life to senescence. Using finite mixturemodels, we investigated the expression of individual heterogeneity in various demographictraits, and examined the origin of these among-individual differences by considering the natalenvironmental conditions. We found that some individuals consistently outperformed othersduring most of their life. In old age, however, the senescence rate was stronger in males thatshowed high demographic performance at younger ages. Variation in individual quality seemedstrongly affected by extrinsic factors experienced during the ontogenetic period. We found thatindividuals born in years with high population density tended to have lower performancesduring their lifespan, suggesting delayed density dependence effects through individual quality.Our study showed that among-individual differences could be important in structuringindividual life history trajectories, with substantial consequences at higher ecological levelssuch as population dynamics.
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