Once thought extinct, giant stick insects confirmed back from the dead
Extinction is permanent, but there are rare cases where creatures we thought had died out suddenly turn up alive and well. That's the story of Lord Howe Island stick insects (or "tree lobster"), which went extinct on their native island in the 1920s and were apparently rediscovered elsewhere decades later. There were questions about whether the living insects were the same species, but now, genetic tests have confirmed that Lord Howe Island stick insects really are back from the dead.
The most famous story of this kind of resurrection is the coelacanth, which was known only from dinosaur-era fossils and presumed extinct, until living specimens were discovered in 1938. In 2013, the Australian Night Parrot was rediscovered in the wild more than a century after the last confirmed sighting. And the Tasmanian tiger, last seen alive in 1936, might soon join the club too, if a new scientific expedition following recent reported sightings turns up evidence of its continued existence.
For the Lord Howe Island stick insect, the trouble began in 1918 when a shipwreck stranded a population of black rats on the small island. Within a few years, the ravenous rodents had wiped out the once-common bugs. But that's not the end of the story: in 1964, freshly-dead specimens were found on the nearby island of Ball's Pyramid, and in 2001 live insects were found and later brought back to the Melbourne Zoo, where they were successfully bred in captivity.
But the identity of the live insects wasn't completely clear. When the Ball's Pyramid bugs were compared side-by-side with Lord Howe Island specimens preserved in a museum since before the extinction, the two insects looked quite different. So were they the same species, or just closely related?
To answer the question, researchers from the Okinawa Institute of Science and Technology Graduate University (OIST), Zoos Victoria and the CSIRO conducted genetic tests on the insects. They put together mitochondrial genomes from specimens bred in captivity, descended from those found on Ball's Pyramid, as well as those from preserved specimens collected about 100 years ago from Lord Howe Island, and then compared the pair.
Despite their skin-deep differences, the genomes of the two insects were extremely similar. Their DNA diverged by less than one percent, which is well within the limits to declare that both belong to the same species. The long-lost Lord Howe Island stick insect is officially not extinct.
"In this case, it seems like we're lucky and we have not lost this species forever, although by all rights we should have," says Professor Alexander Mikheyev, lead author on a research paper describing the genetic tests. "We get another chance—but very often we do not. The stick insect [story] illustrates the fragility of island ecosystems, and in particular, how vulnerable they are to manmade change like invasive species. It just took one shipwreck, and the fauna of the island has been altered in such a fundamental way."
The Lord Howe Island stick insect may have survived extinction, but that doesn't mean our work is done: researchers estimate there may be as few as 20 or 30 specimens in the wild on Ball's Pyramid. Bolstered by the success of the captive breeding program, the next steps are to reintroduce a population to their original homeland of Lord Howe Island – after the invasive rats have been eradicated, that is.
The research was published in the journal Current Biology.