Data from: Non-parallel impacts of predators on the evolution of colouration plasticity in Trinidadian killifish

Animal colouration is a key trait affecting survival and reproduction, yet
the evolutionary drivers of colouration plasticity remain poorly
understood. Here, we examine how predation shapes both baseline
colouration and physiological colouration plasticity in the Trinidadian
killifish (Anablepsoides hartii). This species inhabits streams that vary
in fish predator presence, creating a replicated natural experiment across
three rivers. We hypothesised that fish from high-predation sites would
exhibit lighter baseline colouration due to associations with open canopy
and increased light, and that predation would select for stronger
plasticity in background-induced colour change. We assessed colouration
before and after exposure to black or white backgrounds and analysed
variation by predation regime, river, and sex. Our results show that
baseline colouration differed significantly by predation regime, river
identity, and sex, with high-predation fish generally lighter. A. hartii
also displayed strong plasticity, darkening on black backgrounds and
lightening on white. However, the effect of predation on plasticity was
inconsistent across rivers, suggesting that local ecological factors
mediate these responses. Our study provides rare empirical evidence for
both baseline and plastic variation in colouration driven by ecological
context, offering new insight into how phenotypic plasticity evolves in
response to environmental pressures like predation.