Data from The proteomic basis of temperature-dependent warning colour variation in an aposematic insect

Aposematic colouration in animals advertises prey toxicity and unpalatability to predators. Despite the expectation of stabilising selection on warning signals, intra-specific variation in aposematic signals is widespread, and often thought to be the result of factors including temperature or diet. A colour mutation has been identified in a laboratory population of the aposematic seed bug Lygaeus simulans. The mutant allele segregates as a single Mendelian locus and is recessive to the wild-type allele. Wild-type adults exhibit the typical red and black pattern common amongst many aposematic insects, while the “pale” mutants are yellow and black. However, anecdotal observations have suggested that phenotype of the mutant allele is temperature dependent. Here, we investigated colour and life-history variation in both wild-type and mutant individuals across three rearing temperatures and also identified a potential molecular mechanism underlying the mutant phenotype. We confirmed that L. simulans colouration is temperature sensitive, with both mutant and wild-type individuals being increasingly red at low temperatures (24°C). Life-history traits such as body weight and length were also reduced at 24°C. SWATH-proteomic analysis found clear protein differences between the two morphs, including Glutathione S-transferase (GST), a protein involved in detoxification and oxidative state. Analysis of GST activity showed higher activity in pale mutants compared to wild-types. Furthermore, in males this difference mirrored the effect on colour, disappearing at 24°C, although this was not the case in females. Our results show a unique aposematic colour variation and provide novel molecular insights into the underlying mechanisms of aposematic colouration in insects.