Endocrine regulation of beetle horn polyphenism

Developmental plasticity, the ability of organisms to produce distinct phenotypes in response to environmental factors, can play a critical role in adaptation and diversification. Onthophagine horned beetles have emerged as a powerful model system for investigating the molecular mechanisms underlying plasticity and their evolution. Here, we synthesize our current understanding of the role of key insect hormones (juvenile hormone, ecdysone, and the insulin/insulin-like growth factor signaling pathway) and their interactions with major genetic regulators of horn development, doublesex and Hedgehog signaling. We contrast the mechanisms of plasticity in horned beetles with those in other insect species, highlighting critical gaps in our understanding of the interactions linking hormones, nutrition-sensitive signaling pathways, and developmental genetic regulators. Finally, we discuss how novel genomic and functional genetic tools, combined with integrative approaches, offer promising opportunities to unravel these complex mechanisms.