Reproductive individuality of clonal fish raised in identical environments and its link to early-life behavioral individuality

Genetic and environmental differences are by far the most studied drivers underlying phenotypic variation. However, a growing number of studies finds among-individual variation that is unexplained by genetic or apparent environmental differences. Up to now, it remains an open question whether such seemingly stochastic variation has fitness consequences. To address this question, we performed a tightly controlled long-term life-history experiment with naturally clonal fish (Poecilia formosa) separated directly after birth into near-identical environments. Maintaining highly standardized conditions for 280 days, we first recorded individuals for 10 hours per day over the first 28 days of their lives, characterizing early-life behavioral profiles (activity and feeding behavior). We then measured the complete reproductive profiles of these individuals over an average of 4.5 successive broods per individual, quantifying in total 2522 offspring from 152 broods. Standard lengths of focal individuals were measured once a week. We estimated the growth coefficient (K), maximum predicted (i.e., asymptotic) size (Linf), and predicted size at parturition for each focal individual by fitting individual von Bertalanffy growth curves.