A high-speed chase across the Panama Canal in a Boston Whaler may sound like the beginning of another James Bond filmbut the protagonist of this story brandishes a butterfly net and studies the effects of climate change on insect migrations at the Smithsonian Tropical Research Institute.
"Our long-term study shows that El Nio, a global climate pattern, drives Sulfur butterfly migrations," said Robert Srygley, former Smithsonian post doctoral fellow who is now a research ecologist at the US Agricultural Research Service, the chief scientific research agency of the U.S. Department of Agriculture.
Climate change has been linked to changes in the migration of butterflies in North America and Europe but this is one of the first long-term studies of environmental factors driving long-distance migration of tropical butterflies.
For 16 years, Srygley and colleagues tracked the progress of lemony yellow Sulfur butterflies, Aphrissa statira, a species found from Mexico to Brazil, as they migrate across central Panama from Atlantic coastal rainforests to the drier forests of the Pacific coast.
"The El Nio Southern Oscillationa global climate cycleturns out to be the primary cause for increases in the plants that the larvae of these butterflies eat. El Nio results in dry, sunny days in Panama, which favor plant growth. When the plants prosper, we see a big jump in the number of Statira Sulfur butterflies."
Peak Sulfur butterfly migrations take place a month after the rainy season begins in Panama. Because butterfly developmentfrom egg to larva to pupa to adulttakes about 22 days in the laboratory, Srygley thinks that these butterflies lay their eggs on new leaves produced by vines only four or five days after the rains begin. His team tracked the production of new leaves by two of the butterflies' host plants for 8 years. Drier years resulted in more new leaves.
The number of migratory butterflies was grea
|Contact: Beth King|
Smithsonian Tropical Research Institute