Like many great architects of the human world, the critters that have helped shape Australia's arid Outback are descended from immigrants. In a new paper, researchers reveal that the Nasutitermes triodiae, or "cathedral termites" as they are more commonly known, are not indigenous to the landscape. Rather, they crossed vast distances, took advantage of relaxed immigration policies and adapted to an alien landscape to eventually started building some of the most remarkable structures in the animal kingdom.

So how did they make it all the way Down Under? Termite specialist Nathan Lo, an associate professor at the University of Sydney, believes three things were probably involved: a fallen tree with a termite's nest on it, ocean currents and luck of the draw.

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"We found that the ancestors of Australia's fortress-building termites were coastal tree-dwellers, which arrived in Australia by rafting long distances over the oceans from either Asia or South America," he says.

DNA sequencing revealed that today's mound-building cathedral termites can trace their lineage to tree-dwellers from these continents that arrived and colonized Australia three times over the course of 20 million years.

When they first arrived, these accidental immigrants continued their usual practice of building their nests in trees, but as the environment began to grow more arid, shifting from woodlands to grassland habitats in subtropical savannahs and central Australia, the termites transitioned from feeding on wood to grass and litter as they adapted to the changes around them. Their search for moisture eventually led them to build mounds on the ground. In other words, it was adapt or die.

"Once in Australia, they continued to build their nests in trees, but later descended and began building mounds on the ground instead," says Lo, adding that their evolution could be seen as a parallel to ours. Both species have produced great architects and, like them, human beings also lived in tree tops before making their way to the ground.

That said, if you want to take this point of comparison a step further, the termites' descent to the ground actually predates ours. Up till four million years ago, human beings were still making their homes in trees. And while we might regard skyscrapers, such as Dubai's 830-meter (2,723-ft) Burj Khalifa, as impressive feats of human engineering, a cathedral termite might regard the fanfare surrounding them as a little overblown given that building such mega-structures – relatively speaking – with little more than sand, saliva and fecal matter, is what they do every day.

Some of these cathedral termite mounds can reach as high as eight meters (26 ft), which is no small achievement given that a worker termite is only around three millimeters in height, or less than the size of your thumbnail. In human terms, these mounds would be the equivalent of four Burj Khalifas stacked on top of each other, says Lo.

As iconic as their mounds are to the landscape, they are also a symbol of the cathedral termite's ability to adapt and integrate. Though they might have descended from non-indigenous species, these termites have evolved to become a vital part of the ecosystem, helping maintain the health of the soil and providing an important food source.

In the animal kingdom, it is not uncommon for species to die out, and it is the cathedral termites' capacity to "disperse over oceans – and to evolve the ability to build mounds and feed on novel substrates in the face of significant environmental change" that has made them "one of the most ecologically successful groups of termites" in the country, conclude the authors of the study.

The study was published in Biology Letters.

Source: University of Sydney

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