Natures wonders: dragonflies' yearly migration (Introduction)

by David Turell , Thursday, March 03, 2016, 00:50 (3186 days ago) @ David Turell

A tiny dragonfly flies 4,400 miles from India to Africa each year:-https://www.sciencedaily.com/releases/2016/03/160302150020.htm-"Biologists at Rutgers University-Newark (RU-N) who led the study -- which appears in the journal PLOS ONE -- say the evidence is in the genes. 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 genetic profiles so similar that there is only one likely explanation. Apparently -- somehow -- these insects are traveling distances that are extraordinarily long for their small size, breeding with each other, and creating a common worldwide gene pool that would be impossible if they did not intermingle.-***-"Dragonflies, in fact, have already been observed crossing the Indian Ocean from Asia to Africa. "They are following the weather," says Daniel Troast, who analyzed the DNA 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."-***-"Flight patterns appear to vary. The hardiest of the dragonflies might make the trip nonstop, catching robust air currents or even hurricane winds and gliding all the way. Others may, literally, be puddle jumpers. Pantala need fresh water to mate and lay their eggs -- and if while riding a weather current they spot a fresh water pool created by a rainstorm -- even on an island in the middle of a vast ocean -- Ware and Troast say it's likely they dive earthward and use those pools to mate. After the eggs hatch and the babies are mature enough to fly -- which takes just a few weeks -- the new dragonflies join the swarm's intercontinental and now multi-generational trek right where their parents left off.-***-"What the Rutgers scientists have discovered puts this dragonfly far ahead of any identified insect competitor. "Monarch butterflies migrating back and forth across North America were thought to be the longest migrating insects," traveling about 2,500 miles each way, says Troast, "but Pantala completely destroys any migrating record they would have," with its estimated range of 4,400 miles or more. It also exceeds Charles Lindbergh's celebrated solo flight from New York to Paris by at least several hundred miles.-"Pantala leaves many of its fellow dragonflies even farther behind. The mysteries of evolution are such that while Pantala and its cousin the Green Darner (Anax junius) have developed into world travelers, Ware says that by contrast, other members of the family "don't ever leave the pond on which they're born -- traveling barely 36 feet away their entire lives.'"-Comment: It is not known yet how they are guided on their trips. They appear to follow seasonal winds, but there may well be more to it, like following magnetic fields.