It's in the genes
The fritillary live in distinct patches -- rocky outcroppings containing plants that serve as food and provide a hospitable home for the butterfly larvae to spend the winter. There are about 4,000 such patches on the Ålands, with about 500 patches occupied in a given season, Hanski has found. Some of the patches are farther apart than most individual butterflies can migrate, Fescemyer said.
Each year, new populations begin in some patches while others go extinct because of parasites, disease and the disappearance of plants that serve as food and shelter. Populations established on an isolated patch may require a good flier to reach a new patch to start a new population.
Flight capability varies quite a lot among females, who carry the eggs and establish new populations. For those reasons, natural selection on flight and reproductive capability acts primarily on the females.
Travelers reproduce more quickly
This study examined whether there is a difference in physiology between the females in the newly established populations and females in the older populations. The researchers found out there are.
The study looked at seven patches which had not been colonized the year before and six old populations, Fescemyer said. Hanski's group collected larvae from the seven new patches and reared them on host plants in the laboratory, where they moved to the pupae stage.
Fescemyer recorded when the pupa emerged to become butterflies and periodically collected individual butterflies to determine the number of mature eggs they carried.
"The females from the new patches develop very quickly," Fescemyer said. They developed mature eggs sooner (three days after emerging from the pupa) which could enable them to mate and lay eggs soone
Source:American Physiological Society