ABSTRACT
BACKGROUND: Insects exhibit a diversity of environmentally sensitive phenotypes that allow them to be an extraordinarily successful group. For example, mandible size in male stag beetles is exquisitely sensitive to the larval nutritional environment and is a reliable signal of male condition. RESULTS: To date, studies of how such phenotypically plastic traits develop have focused on two types of mechanistic processes. Local, tissue-specific genetic mechanisms specify the shape and approximate final size of structures, whereas whole-animal hormonal signaling mechanisms modulate trait growth in response to environmental circumstance, including the body size and nutritional state of each individual. Hormones such as juvenile hormone, ecdysteroids, and/or ligands of the insulin-signaling pathway specify whether traits grow and regulate how much growth occurs across a diversity of insect groups. What remains to be shown is how the local, tissue-specific developmental genetic pathways interact with these whole animal hormonal signaling pathways during development to yield phenotypically plastic patterns of trait growth. CONCLUSIONS: Because the Fat/Hippo signaling pathway coordinates trait growth and development through its interactions with morphogens and hormonal pathways, we propose that Fat/Hippo signaling is a missing mechanistic link coordinating environmentally sensitive trait development in insects. Developmental Dynamics 244:1039-1045, 2015. © 2015 Wiley Periodicals, Inc.
