title: Comparative transcriptomics of convergent evolution: different genes but conserved pathways underlie caste phenotypes across lineages of eusocial insects.
abstract: An area of great interest in evolutionary genomics is whether convergently evolved traits are the result of convergent molecular mechanisms. The presence of queen and worker castes in insect societies is a spectacular example of convergent evolution and phenotypic plasticity. Multiple insect lineages have evolved environmentally induced alternative castes. Given multiple origins of eusociality in Hymenoptera (bees, ants, and wasps), it has been proposed that insect castes evolved from common genetic "toolkits" consisting of deeply conserved genes. Here, we combine data from previously published studies on fire ants and honey bees with new data for Polistes metricus paper wasps to assess the toolkit idea by presenting the first comparative transcriptome-wide analysis of caste determination among three major hymenopteran social lineages. Overall, we found few shared caste differentially expressed transcripts across the three social lineages. However, there is substantially more overlap at the levels of pathways and biological functions. Thus, there are shared elements but not on the level of specific genes. Instead, the toolkit appears to be relatively "loose," that is, different lineages show convergent molecular evolution involving similar metabolic pathways and molecular functions but not the exact same genes. Additionally, our paper wasp data do not support a complementary hypothesis that "novel" taxonomically restricted genes are related to caste differences.
authors.affiliation: Program in Bioinformatics and Computational Biology, Iowa State University Department of Ecology, Evolution, and Organismal Biology, Iowa State University berens.ali@gmail.com.
authors.forename: Ali J
authors.initials: AJ
authors.lastname: Berens
authors.affiliation: Department of Biological Sciences, North Carolina State University Department of Entomology, North Carolina State University W. M. Keck Center for Behavioral Biology, North Carolina State University.
authors.forename: James H
authors.initials: JH
authors.lastname: Hunt
authors.affiliation: Program in Bioinformatics and Computational Biology, Iowa State University Department of Ecology, Evolution, and Organismal Biology, Iowa State University Department of Entomology, Iowa State University.
authors.forename: Amy L
authors.initials: AL
authors.lastname: Toth
mesh_terms: D000818:Animals; D016000:Cluster Analysis; D019295:Computational Biology; D019143:Evolution, Molecular; D020869:Gene Expression Profiling / Q000379:methods*; D017344:Genes, Insect / Q000235:genetics* / Q000502:physiology; D006927:Hymenoptera / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D012919:Social Behavior; D059467:Transcriptome / Q000235:genetics*
keywords: castes; convergent evolution; gene expression; phenotypic plasticity; social insects; transcriptome