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

Area of Science:

• * Insect physiology and developmental biology
• * Animal behavior and migration
• * Climate change adaptation in wildlife

Background:

• * Monarch butterflies (Danaus plexippus) exhibit a migratory diapause, a crucial adaptation for winter survival.
• * The precise environmental and physiological mechanisms timing diapause termination remain poorly understood.
• * Understanding diapause timing is vital for predicting monarch population responses to climate change.

Purpose of the Study:

• * To investigate the environmental and physiological factors controlling the termination of monarch butterfly diapause.
• * To identify molecular mechanisms underlying the internal diapause termination timer.
• * To elucidate how environmental cues integrate with internal physiological processes to regulate diapause timing.

Main Methods:

• * Subjecting western North American monarchs to controlled environmental chamber conditions.
• * Employing comparative transcriptomics to identify molecular controllers of diapause termination.
• * Analyzing hormonal signaling pathways including juvenile hormone (JH) and ecdysteroids.

Main Results:

• * Calcium signaling was identified as a mediator of environmental sensitivity in the diapause timer.
• * Juvenile hormone (JH) signaling showed spontaneous changes, preparing for future environmental responses.
• * Epigenetic mechanisms are implicated as the proximate timing mechanism for diapause termination.

Conclusions:

• * The study modularized components of an internal diapause termination timer, highlighting calcium signaling and epigenetics.
• * Key hormonal pathways (ecdysteroid, JH, insulin/IGF) are targets of the diapause program.
• * Findings provide insights into biological timing and monarch butterfly adaptation to climate change.