Study: Tougher Butterflies Migrate Farther

Running away from home can be a rewarding survival technique for female Glanville fritillary butterflies.

New research shows the more venturesome females among the butterflies are stronger fliers and can reproduce more quickly than their less mobile sisters, allowing them to establish new colonies.

The finding, presented here this week at a meeting of the American Physiological Society, could help scientists understand how other species might respond to habitat destruction.

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The animals best able to migrate are more likely to survive and reproduce, the thinking goes.

"We may be selecting for genes that enhance the dispersal or migratory capability of animals when we fragment the landscape," said Howard Fescemyer of Pennsylvania State University. "What we learn could apply to any organism that has to move to find food."

Spotty range

The Glanville fritillary butterflies (Melitaea cinxia) are widespread and common in Europe and parts of Asia. They live on landscapes spotted with rocky outcroppings, with separate colonies residing on different rocky areas, surrounded by vegetation that provides food and shelter.

On the Aland Islands, located between Finland and Sweden in the Baltic Sea, where the research was done, there are 4,000 such patches, ringed with a skirt of plants and ranging in diameter from six feet to 50 feet or more.

The females bear the brunt of transporting themselves and their eggs from one patch to another.

Each year, new populations begin in some patches, while others go extinct because of parasites, disease and the disappearance of plants.

Some of the patches are farther apart than most fritillary butterflies can travel, Fescemyer said. To make the trip, the females would have to be relatively strong fliers.

In fact, flying ability varies a lot among the females.

Early bloomers

Fescemyer and his colleagues looked at the populations of seven newly colonized patches, plus those of six more established patches.

They collected butterfly larvae — e.g., caterpillars — from each patch and raised them in a lab, monitoring the caterpillars as they transformed into pupae and then emerged as adult butterflies.

Female fritillary butterflies begin to develop eggs, within strands of ovaries connected like a pearl necklace, as soon as they become adults.

But the rates of egg maturity between the two groups were different.

The females from the newly established patches developed mature eggs three days after emerging as adults, a day sooner than females from the older populations.

The females from new patches also had more vitellogenin, a protein that forms egg yolk, which provides the embryos with nutrients. Researchers suspect that allowed their eggs to mature faster.

Successful lifestyle

The early egg-makers have a wing up in that they can both mate and lay eggs sooner than those from the older patches.

"If you are going to move, you better get busy and do it," Fescemyer told LiveScience.

A lot can happen in a day. The butterflies live just two to three weeks after emerging from the pupae, so they have to produce eggs quickly.

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