The Mysterious Case of the Lord Howe Island Tree Lobster
Meet the Lord Howe Island Tree Lobster (Dryococelus australis).
Credit: Thomas Reischig
This not so little bug, stretching up to 5 inches or 13 centimeters long, was thought to be extinct until 24 of them were found on a lonely outcrop nearly sixteen miles off of its namesake Lord Howe Island in 2001. The tree lobsters (I think you can see how they got that name just by looking at them) were once common on the small island northeast of the Sydney, Australia that is designated as a World Heritage site. They were common, that is, until black rats swam for it from shipwrecked boat to the Island ninety years ago. Rats like to eat bugs, and thus the Island’s native population of “stick” bugs were wiped out.
But this tenacious bug clung to life.
And this is not the first time that the Lord Howe island tree lobster has clung to life after losing its Island home.
Scientists have discovered that the Lord Howe variety tree lobster is older than the island for which it is named.
The Lord Howe tree lobster appears to be harboring even more surprises. As part of an analysis of the evolutionary origin of stick insects, biologist Thomas Buckley of Landcare Research, New Zealand’s main research institute for environmental science, and colleagues collected DNA from three tree lobster groups, including D. australis, and about 70 other stick insect species. The team found that D. australis was more than 20 million years old, 13 million years older than the rocks on Lord Howe Island.
So where did this species evolve? Buckley thinks that the solution lies under the Pacific Ocean. Lord Howe Island is the youngest of an old chain of islands formed as the Indo-Australian tectonic plate travels north over a fixed volcanic center, or hot spot. Older islands are now submerged inactive volcanoes. The Lord Howe tree lobster may have evolved in one of these drowned islands and traveled south as its habitat eroded away, the team reported online 16 December in the Proceedings of the Royal Society B.–ScienceNOW Daily News
How about that? This insect really wants to survive, and has been island-hopping for a good part of its existence. And it seems that DNA analysis has more to tell us about this creepy crawly that just won’t die.
The Lord Howe Island tree lobster is a unique species from two other tree lobsters tested recently by Buckley. The LHI tree lobster and its previously-assumed brethren on New Caledonia and New Guinea evolved apart from one another in a process called convergent evolution.
Convergent evolution is when separate species develop similar evolutionary traits in response to similar environments, despite the fact that they are not closely related. Think wings on birds and bats. Birds and bats are hardly related, but both classes developed wings in response to environmental and evolutionary pressures.
In the case of tree lobsters, you can see how similar (top photo) the New Guinea tree lobster and the Lord Howe Island tree lobsters species are (hi, as in scary), but also how different in the bottom photo where you can see the tree lobsters side by side with another distant relative, a typical stick bug (my infinite thanks to Bug Girl’s Blog for the link to the German site where I got these images).
Credit: Michael Whiting/Thomas Reischig
Again, Thomas Reischig
tree lobster, Lord Howe Island, Australia, extinct, insect, bug, DNA, New Zealand, New Guinea, New Caledonia, World Heritage, stick bugs, convergent evolution, evolution
