Alan Andersen has been collecting and documenting specimens of Australian ant species for 40 years, some 8,000 of which have been taped onto cardboard triangles at a government laboratory in Darwin, in the far north of the country.
Hundreds of specimens are added to the collection each year, most likely new species that do not even have formal scientific names.
When entomologists speak of the global ant diversity hotspot—the place with the highest number of species—they often refer to the savannahs of Brazil and the Amazon rainforest.
But Andersen, a professor, ant expert and ecologist at Charles Darwin University, says the true global center for ants is Australia’s monsoon north, stretching from the Kimberley in Western Australia to the upper end of the Northern Territory and northern Queensland in the east.
“Ants are an important part of Australia’s natural heritage,” says Andersen. “We know what a special place this is for marsupials and lizards. And ants. We are the kingdom of the ant.”
Andersen’s recent research with colleagues, he says, has added further evidence to Australia’s claim to be the global ant capital.
The research looked at specimens from a group of ants called Monomorium Nigrius which has only one species that is formally described in the scientific literature.
But after genetically analyzing 400 specimens, scientists estimate there are likely 200 different species in the group just in monsoon northern Australia, and another 100 in the rest of the country.
“Ant ecologists will say that ant diversity is greatest in the Amazon—there can be more than 2,000 species there,” he says. “But here in monsoon Australia we have at least 5,000.”
Andersen and colleagues wrote that their latest findings are “further evidence that monsoon Australia should be recognized as a global center of ant diversity.”
Andersen and his ant-hunting colleagues are used to discovering hundreds of completely new species.
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A few weeks ago, Andersen walked a trail in Iron Range National Park on Queensland’s remote Cape York Peninsula with graduate student François Brassard.
A 4 mm brownish ant caught his eye. For Andersen, it was clearly some kind of anochet – an unusual genus in Australia.
“It looked like this,” says Andersen, who took it to his lab. The ant was one Anochetus alae – and only the second time it has ever been found (the first time was in Cairns in 1983 and was used years later to officially describe the species).
Andersen analyzed samples collected by colleagues from 100 sites around the Sturt Plateau in the Northern Territory.
The results haven’t been released yet, but Andersen says they’ve counted about 700 species so far, and about half have never been recorded before.
Brassard is Canadian and has studied ants in the US, Macau and Hong Kong. He was skeptical that Australia could top the Amazon for ant species, but no more.
“There are about 100 species of ants in Canada,” he says. “But we find so many here on just a few hectares. The sheer variety is unreal. It just seems like there’s new stuff everywhere.”
Ants are often collected using pit traps – a shallow plastic tray dug a few inches into the ground containing a preservative. Andersen uses ethylene glycol, better known as antifreeze.
His record is 27 species in a 4.5 cm wide trap he set for two days in the Northern Territory’s Kakadu National Park.
It’s a measure of the sheer number of ants in the country.
“People wouldn’t even notice them, even though they’re incredibly plentiful across Australia,” he says. “You can have dozens of colonies in an area as small as 10 by 10 meters.”
Ants play a crucial role in ecosystems. Both create and turn over soil, they spread seeds, some defend plants, and they are all food for other animals.
If you could weigh all of the world’s land fauna, Andersen says that about 20% of the mass would be ingested by ants.
“They’re serious creatures in our environment,” he says. They are recyclers of weapon nutrients. They play an incredibly important role in the flow of energy and nutrients through ecosystems. Ants are down there doing the show.”
A 400-year taxonomic challenge
Andersen began collecting ants 40 years ago, and his collection – and that of many others – is housed at the CSIRO laboratory in Darwin.
Even among these ants – almost all of which are unique to Australia – only 1,500 have been officially named by taxonomists. The collection is one of the largest in the world.
When scientists like Andersen apply new techniques to discover the true diversity among organisms, it poses a major challenge for taxonomists — the scientists who meticulously describe new species and then publish the details in peer-reviewed journals.
Prof Andy Austin is the Director of Taxonomy Australia. He says wildly diverse groups of animals — like ants — are heralding a quiet revolution for the profession.
Traditional methods of drafting detailed descriptions, drawings, and creating flowcharts known as keys to distinguish one species from another are impractical when new scientific methods offer thousands and thousands of new candidates.
“You can’t continue with the traditional taxonomy that was developed a hundred or more years ago,” he says.
Austin himself described about 650 new species – mostly wasps – but it occupied most of his 40-year career.
“For Australia, we describe about 1,200 species of all organisms every year. It would take 400 years to wipe out all Australian biota and that is unacceptable for so many reasons.”
He says the new generation of taxonomists uses new techniques, such as describing new species with automated imaging and genetic data. This brings the challenge of describing thousands of new ant species within reach.
“We can’t ask sensible questions about our flora and fauna until we know what’s actually on the continent,” he says.
As the climate changes and land is cleared, “there will likely be species that go extinct before we have a chance to document them.”