黄蜻是世界上飞行距离最远的生物

A dragonfly barely an inch and a half long appears to be animal world's most prolific¹ long distance traveler - flying thousands of miles over oceans as it migrates from continent to continent - according to newly published research. Biologists at Rutgers University-Newark (RU-N) who led the study - which appears in the journal PLOS ONE - say the evidence is in the genes³. They found that populations of this dragonfly, called Pantala flavescens, in locations as far apart as Texas, eastern Canada, Japan, Korea, India, and South America, have genetic⁴ profiles so similar that there is only one likely explanation. Apparently⁵ - somehow - these insects are traveling distances that are extraordinarily⁶ long for their small size, breeding with each other, and creating a common worldwide gene² pool that would be impossible if they did not intermingle.

 

"This is the first time anyone has looked at genes to see how far these insects have traveled," says Jessica Ware⁷, an assistant professor of biology on the faculty⁸ of RU-N's College of Arts and Sciences and senior author of the study. "If North American Pantala only bred with North American Pantala, and Japanese Pantala only bred with Japanese Pantala," Ware says, "we would expect to see that in genetic results that differed from each other. Because we don't see that, it suggests the mixing of genes across vast geographic⁹ expanses."

 

But how do insects from different continents manage to meet and hook up? These are not large birds or whales that one would expect to travel thousands of miles. Ware says it appears to be the way their bodies have evolved. "These dragonflies have adaptations such as increased surface areas on their wings that enable them to use the wind to carry them. They stroke, stroke, stroke and then glide¹⁰ for long periods, expending¹¹ minimal¹² amounts of energy as they do so."

 

Dragonflies, in fact, have already been observed crossing the Indian Ocean from Asia to Africa. "They are following the weather," says Daniel Troast, who analyzed¹³ the DNA¹⁴ samples in Ware's lab while working toward his master's degree in biology, which he earned at the university in 2015. "They're going from India where it's dry season to Africa where it's moist season, and apparently they do it once a year."

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