Data from: Monarch butterflies use an environmentally sensitive, internal timer to control overwintering dynamics

The monarch butterfly (Danaus plexippus) complements its iconic migration
with diapause, a hormonally controlled developmental program that
contributes to winter survival at overwintering sites. Although timing is
a critical adaptive feature of diapause, how environmental cues are
integrated with genetically-determined physiological mechanisms to time
diapause development, particularly termination, is not well understood. In
a design that subjected western North American monarchs to different
environmental chamber conditions over time, we modularized constituent
components of an environmentally-controlled, internal diapause termination
timer. Using comparative transcriptomics, we identified molecular
controllers of these specific diapause termination components. Calcium
signaling mediated environmental sensitivity of the diapause timer, and we
speculate that it is a key integrator of environmental condition (cold
temperature) with downstream hormonal control of diapause. Juvenile
hormone (JH) signaling changed spontaneously in diapause-inducing
conditions, capacitating response to future environmental condition.
Although JH is a major target of the internal timer, it is not itself the
timer. Epigenetic mechanisms are implicated to be the proximate timing
mechanism. Ecdysteroid, JH, and insulin/insulin-like peptide (IIS)
signaling are major targets of the diapause program used to control
response to permissive environmental conditions. Understanding the
environmental and physiological mechanisms of diapause termination sheds
light on fundamental properties of biological timing, and also helps
inform expectations for how monarch populations may respond to future
climate change.