No evidence that proteome composition is associated with realised thermal limit and dietary niche breadth in butterflies

Abstract

Amino acids are the building blocks of proteins that perform essential physiological functions. Theory suggests that the proteome composition, the amino acid frequencies across all proteins in a genome, is associated with an organisms optimal growth temperature, offering insights into species temperature limits. However, this hypothesis, based on prokaryotes, has not been tested in complex multicellular eukaryotes where many amino acids are strictly acquired through diet. Here, we analysed amino acid frequencies in the proteomes of orthologous and non-orthologous genes from 35 butterfly species to test for correlations with maximum observed temperatures and diet breadth. Using a comparative approach, we found no evidence that proteome composition correlates with temperature or diet breadth. Our findings suggest that animal proteome composition is likely shaped more strongly by energetic and biophysical constraints rather than by ecological factors.