The Monarch butterfly is famous for its ability to travel up to 2,000 miles from North America to central Mexico every fall. Now, it's enjoying fame of a different sort. In the November 23rd issue of Cell, researchers report the full genomic sequence of this iconic butterfly. The new genome is the first for any butterfly. It is also the first complete genome of any long-distance migrant.
"With this genome sequence in hand, we now have an overwhelming number of opportunities to understand the genetic and molecular basis of long-distance migration," says Steven Reppert of the University of Massachusetts Medical School.
Reppert's team has been studying the monarch migration for years, with a particular interest in how their brains incorporate information in time and space to find their way. Monarchs are all the more remarkable given that migrating butterflies are always at least two generations removed from those that made the journey the previous fall. "It is in their genes," Reppert said.
The researchers focused their genome analysis on pathways known to be critical for this migration, including those responsible for vision, the circadian clock, and oriented flight. The genome also revealed the complete set of genes required for synthesizing juvenile hormone. Changes in that hormone are required for migrating butterflies to shut down reproduction and extend their lifespan up to nine months. By comparison, non-migrants only live for about a month.
Comparisons of the new monarch genome with other insect genomes also reveal that butterflies and moths (Lepidoptera) are the fastest evolving insect order yet examined.
"Overall," the researchers write, "the attributes of the monarch genome and its proteome provide a treasure trove for furthering our understanding of monarch butterfly migration; a solid background for population genetic analyses between migratory and non-migratory populations; and a basis for future genetic comparison of the genes involved in navigation yet to be discovered in other long-distance migrating species, including vertebrates like migratory birds."