plays key role in monarch butterfly's miraculous migration
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[October 02, 2014]
By Will Dunham
WASHINGTON (Reuters) - The 3,000-mile
(4,800-km) mass migration of monarch butterflies in North America is one
of the insect world's fantastic feats, with millions embarking on the
arduous journey from as far north as Canada down into Mexico and the
California coast each autumn.
Scientists who scoured the genome of these colorful insects
offered new insight on Wednesday into this annual airborne
adventure. They pinpointed a single gene related to flight muscle
efficiency that plays a major role in the monarch butterfly's
Their study, published in the journal Nature, also identified the
gene behind the butterfly's striking orange-and-black coloration.
"I find it amazing that these little butterflies live for months and
fly thousands of miles to perform this annual migration," said one
the researchers, University of Chicago professor of ecology and
evolution Marcus Kronforst.
"Our study shows that monarchs have been doing this every year for
millions of years. There is nothing else like this on the planet,"
The number of migrating monarchs has plummeted in recent years.
Kronforst said while an estimated one billion monarch butterflies
migrated to Mexico in 1996, that number stood at about 35 million
this past winter. Threats to them include habitat loss due to human
activities, pesticides that kill milkweed and climate change,
While mainly a North American species, monarch populations also can
be found in Central America, South America and elsewhere. Those
outside North America do not migrate.
The researchers carried out genome sequences on 92 monarch
butterflies from around the world including non-migratory ones as
well as on nine butterflies from closely related species. To study
the genetic basis for migration, they compared the genetic blueprint
of migratory monarchs to those that do not migrate.
"One gene really stood out from everything else in the genome,"
It was a gene related to collagen, the main ingredient in connective
tissue, that was essential for flight muscle function. The
researchers were surprised to find the gene was less active, not
more active, in migratory butterflies. So rather than making them
big, powerful fliers the gene favored enhanced flight efficiency.
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"An analogy might be the difference between marathon runners
(migrating butterflies) and sprinters," Kronforst said.
Shuai Zhan, a biologist at the Shanghai Institutes for Biological
Sciences, said the study determined that the species originated in
North America, contradicting the hypothesis that monarchs evolved
from tropical ancestors.
Adult monarch butterflies boast wings that are orange with black
veins and white spots along the outside edges. Their wingspan is
about 4 inches (10 cm) and their bodies are black.
Scientists say their orange color tells potential predators they
taste awful and are toxic to eat thanks to chemicals from the
milkweed plants that nourish them in their larval state.
Kronforst said monarch butterflies living east of the Rocky
Mountains spend their winters in Mexico to escape the cold weather
while those west of the Rockies spend winters on the California
coast before returning home in the spring.
(Reporting by Will Dunham; Editing by James Dalgleish)
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