Environmental effects on colour variation and the underlying mechanisms of colour production in an aposematic bug

Aposematism combines conspicuous visual signals, e.g. red, orange, or yellow, with secondary defences such as toxicity or distastefulness, to advertise the unpalatability and unprofitability of the individual to potential predators. Aposematic colour is therefore expected to show reduced variation, as the more common and consistent the signal is in the population, the easier it is for predators to learn to associate it with unpalatability. Nonetheless, aposematic colour is often variable within species. To understand the creation and maintenance of variation in aposematic signals, the thesis focuses on environmental factors and mechanisms that contribute to the colour variation in an aposematic bug, Lygeaus simulans. We found that both temperature and diet affect bug colouration. These environmental factors cause coordinated changes in physiological traits, secondary defence, and protein expression. Furthermore, when exploring the underlying mechanisms through pigment and genomic analysis, we found that the colour variation seen across morphs and rearing temperatures was associated with variation in the pteridines, and a major-effect locus was involved in the colour differences between morphs. This research highlights how aposematic colour variation is shaped by environment, pigment substances, and genetic architecture, with important implications for how aposematic colours can evolve and diversify.