In a cautionary tale for civic scientists trying to rescue North America's legendary Monarch butterfly, new research has revealed that captive-reared butterflies sometimes fail are able to migrate – some as a result of missing genes and others for lack of proper environmental traits.
A doctoral student discovered this genetic deficiency after buying and tying dozens of monarchs – a common way to test which direction an insect wants to fly. Tailed wild-caught monarchs consistently head south, in the same direction they fly to Mexico on their annual voyages from the US and Canada. But neither monarchs from commercial sources nor native people raised indoors did so. They tended to fly in random directions.
To see why the monarchs did not want to fly south, the researchers sequenced the DNA of some butterflies and compared them to the already sequenced monarch genomes. They found many differences, but could not determine a particular gene. But even with the right genes, domestic butterflies bred indoors could not steer in the right direction. The researchers believe that butterflies bred outdoors orientate to the south, while butterflies grown indoors do not receive the environmental signals that would signal them to fly south. They report this today in the Proceedings of the National Academy of Sciences .
Throughout their long history of development, monarchs who have spread to Africa, Australia, South and Central America, and Hawaii have stopped migrating. With mild local conditions, they do not have to go anywhere else. However, butterflies in colder climates such as North America do not survive the winter if they do not migrate.
The recent call by the US government to list species as threatened could therefore be justified. The findings also suggest that schoolchildren and hobbyists raising monarchs to strengthen the population of the species may want to source it locally and raise it outdoors for the entire life cycle.