Scientists find first evidence that butterflies crossed the ocean

Early one morning in late October 2013, entomologist Gerard Talavera saw something very unusual — a flock of colorful butterflies stranded on a beach in French Guiana.

The Painted Lady, or Type, Vanessa Cardoy, It is one of the most widespread butterflies in the world, but it is not found in South America. However, they were lying on the sand of the eastern shores of the continent, their wings torn and full of holes. Given their condition, Dr Talavera, who works at the Botanical Institute of Barcelona in Spain, guessed they were recovering from a long journey.

The insect is a champion of long-distance travel, routinely crossing the Sahara on a journey from Europe to sub-Saharan Africa, covering up to 9000 miles. Could they also have made a 2,600-mile voyage across the Atlantic without anywhere to stop and refuel? Dr. Talavera wanted to know.

Tracking long-range insect movements is difficult. Tools such as radio trackers are too large for the frames of small, delicate insects, and radar allows only specific locations to be monitored. Scientists have had to rely on educated guesses and observations of citizen scientists to piece together travel patterns.

“We see butterflies appearing and disappearing, but we are not directly proving the links, we are just making assumptions,” Dr. Talavera said.

In 2018, it is Develop a method to use a common genetic sequencing tool To analyze the DNA of pollen grains. Pollen grains stick to insects such as butterflies when they feed on flower nectar. Dr. Talavera used a method called DNA barcoding to sequence the pollen’s DNA and determine which plant it came from. Later, the DNA can be traced to geographic plants to chart the insect’s path.

in Published paper On Tuesday in the journal Nature Communications, Dr. Talavera and his team described a crucial clue to deciphering the mystery of stranded butterflies: Pollen clinging to butterflies in French Guiana matches flowering shrubs in West African countries. These shrubs bloom from August to November, which corresponds to the arrival schedule of butterflies. This indicates that the butterflies crossed the Atlantic Ocean. The idea was confusing. But Dr. Talavera and his team were careful not to jump to conclusions.

In addition to studying the pollen, the researchers sequenced the butterflies’ genomes to trace their lineage and found that they have European-African roots. This rules out the possibility that they flew over the Earth from North America. They then used an insect-tracking tool called isotope tracing to confirm that the butterflies’ origins were in Western Europe, North Africa, and West Africa. By adding weather data showing favorable winds blowing from Africa to America, they were preparing to make a massive discovery.

“This is an amazing piece of biological detective work,” said David Lohman, an evolutionary ecologist at the City College of New York, who was not involved in the work. Dr. Talavera’s research, which resembles a forensic detective style, supported the conclusion that the Painted Lady Butterfly made the first transoceanic voyage ever recorded by an insect.

They were likely on their typical route across Africa when they were swept off course by strong winds. Once they crossed the ocean, the butterflies continued to fly until they reached the beach.

Insect migrations are the largest movement of biomass around the world. Over southern England alone, which is amazing 3.5 trillion insects They migrate annually. Their ability to transmit pollen, fungi, and even plant diseases across vast distances highlights the global impact of these tiny creatures. As the Painted Ladies migrate across oceans, scientists may have a better way to track these journeys, experts say.

The results showed that the delicate creatures could endure a difficult and dangerous journey, which would likely last between five and eight days. It also shows how much scientists still have to learn. Jessica Ware, an evolutionary biologist at the American Museum of Natural History, who was not involved in the study, described the study’s methods as “innovative” and added that they “will help us understand migrations.”