Evolution of Immunity-Related Genes in Myrmeciine Ants

Abstract

Pathogenic microorganisms impose strong selection pressures on animal immune systems. Immunity-related genes include the most rapidly evolving genes in insect genomes. In social insects pathogens can be easily transmitted among nest mates. Thus they are very well suited for studying the evolution of immunity-related genes. Here, we study the molecular evolution of immunity-related genes in Australian hopper and bulldog ants (genus Myrmecia), and in the "dinosaur" ant Nothomyrmecia macrops. We cloned and sequenced several immunity-related genes whose products include pathogen recognition, signal transduction, and effector molecules. We discovered positive selection in some but not all immunity-related genes studied in myrmeciine ants applying codon-based comparative analyses. Moreover, we produced a molecular phylogeny facilitating insights into the evolution of phenotypic characters in myrmeciine ants.