The importance of amino acids in the adult diet of male tropical rainforest butterflies

Adult diet is a major factor contributing to life history variation in the Lepidoptera. Amino acids derived from adult feeding, in particular, are suspected to be a major contribution to fitness, but this could be proven in only few species so far. Effects of amino acids in the diet of butterflies were experimentally investigated in 13 species from a Borneo rainforest community (using caged males without mating opportunity). Four species lived substantially longer when given a mix of amino acids additionally to water, sodium and sugar solutions. No significant phylogenetic pattern was found for effects of amino acid feeding, although none of six pierid species were among the taxa with significant effects. Species that do react to amino acids tend to be among the most long-lived taxa in the community, suggesting that amino acids are a key variable to attain long life spans. Weaker effects, or impacts on other fitness-related variables, cannot be excluded in the remaining taxa. Results indicate that adult amino acid intake may not be a rare strategy of few exotic taxa, but is, at least in non-seasonal tropical regions, a common life history trait in a substantial number of butterfly species.