Nutritional specialization and social evolution in woodroaches and termites

Abstract

Woodroach biparental-care and termite sibling-altruism evolved from solitary cockroach ancestors following nutritional specialization on nutrient-deficient dead-wood, but the accompanying genomic changes remained unclear. We sequenced eight new Blattodea species 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 mediating 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, EGFR and Dpp signaling pathways. Thus, most larvae develop as workers via high energy metabolism early on, while 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 allowing large homeostatic colonies to evolve.