[Leps-l] monarchs, reversal of orientation and overwintering temperatures

Chip Taylor chip at ku.edu
Thu Feb 21 13:45:14 EST 2013


http://www.climatecentral.org/news/spring-chill-sends-monarchs-fluttering-north-15634

http://www.cell.com/current-biology/abstract/S0960-9822(13)00087-0

Coldness Triggers Northward Flight in Remigrant Monarch Butterflies

Current Biology, 21 February 2013
Copyright © 2013 Elsevier Ltd All rights reserved.
10.1016/j.cub.2013.01.052

Authors
Patrick A. Guerra
,
Steven M. Reppert
Summary
Each fall, eastern North American monarch 
butterflies (Danaus plexippus) migrate from their 
northern range to their overwintering grounds in 
central Mexico [1,2,3]. Fall migrants are in 
reproductive diapause, and they use a 
time-compensated sun compass to navigate during 
the long journey south [4,5,6]. Eye-sensed 
directional cues from the daylight sky (e.g., the 
horizontal or azimuthal position of the sun) are 
integrated in the sun compass in the midbrain 
central complex region [7,8]. Sun compass output 
is time compensated by circadian clocks in the 
antennae so that fall migrants can maintain a 
fixed flight direction south [9,10]. In the 
spring, the same migrants remigrate northward to 
the southern United States to initiate the 
northern leg of the migration cycle. Here we show 
that spring remigrants also use an 
antenna-dependent time-compensated sun compass to 
direct their northward flight. Remarkably, fall 
migrants prematurely exposed to 
overwintering-like coldness reverse their flight 
orientation to the north. The temperature 
microenvironment at the overwintering site is 
essential for successful completion of the 
migration cycle, because without cold exposure, 
aged migrants continue to orient south. Our 
discovery that coldness triggers the northward 
flight direction in spring remigrants solves one 
of the long-standing mysteries of the monarch 
migration.



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