Data from: Behavioural individuality in clonal fish arises despite near-identical rearing conditions

Behavioural individuality is thought to be caused by differences in genes
and/or environmental conditions. Therefore, if these sources of variation
are removed, individuals are predicted to develop similar phenotypes
lacking repeatable individual variation. Moreover, even among genetically
identical individuals, direct social interactions are predicted to be a
powerful factor shaping the development of individuality. We use tightly
controlled ontogenetic experiments with clonal fish, the Amazon molly
(Poecilia formosa), to test whether near-identical rearing conditions and
lack of social contact dampen individuality. In sharp contrast to our
predictions, we find that (i) substantial individual variation in
behaviour emerges among genetically identical individuals isolated
directly after birth into highly standardized environments and (ii)
increasing levels of social experience during ontogeny do not affect
levels of individual behavioural variation. In contrast to the current
research paradigm, which focuses on genes and/or environmental drivers,
our findings suggest that individuality might be an inevitable and
potentially unpredictable outcome of development.