Non-genetic inheritance of stochastically induced behavioral individuality in a naturally clonal fish

Research on stochastic phenotypic variation (i.e., variation arising despite the apparent absence of genetic and environmental differences) has recently emerged as a rapidly growing area in biological research. But despite growing recognition of both its existence and fitness relevance, it remains unknown whether and to what extent such stochastically induced variation is transmitted across generations, potentially making it an unrecognized contributor to evolutionary processes and the adaptive potential of populations. In order to address this knowledge gap, we here performed a two-generation behavioral screening with a naturally clonal fish: 34 genetically identical mothers and their 232 offspring were separated directly after birth into near-identical environments and tracked continuously at high resolution, constituting a total of [~]19,000 observation hours. We find that consistent among-individual differences in behavioral profiles (i.e., activity and feeding patterns) of both mothers and offspring emerged despite the absence of apparent genetic and environmental differences. Mother feeding behavior - but not mother activity - was positively associated with offspring activity: mothers that spent more time feeding produced more active offspring, explaining [~] 33 % of the total variation in offspring activity. This link between mother and offspring behavior was not mediated by mother size or offspring size at parturition. Our study provides first evidence for the non-genetic transmission of among-individual phenotypic differences that arise despite the apparent lack of genetic or environmental variation, highlighting the potential importance of this variation for evolutionary processes and the adaptability of populations.