Lifespan heterogeneity reflects intrinsic quality, not trade-offs

Abstract Individuals of the same species often display extensive lifespan heterogeneity. However, the factors underlying such heterogeneity remain largely elusive. Here, we examined whether lifespan variation in the naturally short-lived turquoise killifish ( Nothobranchius furzeri ) is caused by reproductive trade-offs. We found that lifespan and reproduction do not trade off: early-life reproductive success positively predicts male lifespan and reflects intrinsic quality. A causal-informed model, where intrinsic quality affects both survival and reproduction, fully recapitulates the empirical data. Together, our results show inter-individual variation in intrinsic quality explains lifespan heterogeneity in a short-lived vertebrate, challenging the view that reproductive costs drive inter-individual lifespan variation.