Nutritional specialization and social evolution in woodroaches and termites.

Abstract

Woodroach biparental care and termite sibling altruism evolved from solitary cockroach ancestors after nutritional specialization on nutrient-deficient deadwood, but the accompanying genomic changes remained unclear. We sequenced eight new species of the order Blattodea, showing stepwise contracted genomes. Woodroach brood rearing remained constrained by deactivated oxidative phosphorylation and peroxisome genes, consistent with slow immature growth. Termites lost key genes that mediate sperm motility, corroborating that reproductive division of labor required monogamous colony founding. They also co-opted many genes from fundamental nutrition-sensitive juvenile hormone, insulin, epidermal growth factor receptor (EGFR), and Decapentaplegic (Dpp) signaling pathways. Thus, most larvae develop as workers by means of high energy metabolism early on, whereas reproductive nymphs highly express energy metabolism genes late in development. These pathways are consistent with obligate dependence on provisioning by specialized workers and feedback loops that allow large homeostatic colonies to evolve.