Alan Andersen has collected and recorded samples of Australian ant species for 40 years with around 8,000 of them glued to cardboard triangles in a government laboratory in Darwin in the far north of the country.
Every year, hundreds of specimens are added to the collection, most of them probably new species that don’t even have formal scientific names.
When entomologists talk about the world’s hotspot for ant diversity – the place with the most species – they often point 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, which stretches from the Kimberley in Western Australia to the top end of the Northern Territory and north Queensland in the east.
“Ants are a huge part of Australia’s natural heritage,” says Andersen. “We realize what a special place this is for marsupials, and for lizards. And ants. We are the kingdom of the ants.”
Andersen’s latest research with colleagues has, he says, added further evidence to Australia’s claim to be the global capital of ants.
The research looked at samples of a group of ants called Monomorium nigrius which has only one species formally described in scientific literature.
But after genetic analysis of 400 specimens, the researchers estimate there are probably 200 different species in the group just in the monsoon north of Australia, and another 100 in the rest of the country.
“Ant ecologists would say that ant diversity is highest in the Amazon – there could 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 were “further evidence that monsoonal Australia should be recognized as a global center of ant diversity.”
Andersen and his ant-seeking colleagues are used to discovering completely new species by the hundreds.
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A few weeks ago, Andersen walked a trail in the Iron Range National Park on Queensland’s remote Cape York Peninsula with graduate student François Brassard.
A 4mm brownish ant caught his eye. For Andersen, it was clearly a type Anochetus – an unusual genus in Australia.
“It had that look,” says Andersen, who brought it back to the lab. The ant was one Anochetus alae – and only the second time it had ever been found (the first occasion was in Cairns in 1983 and was used years later to formally describe the species).
Andersen has analyzed samples collected by colleagues from 100 sites around the Sturt Plateau in the Northern Territory.
The results have not been published yet, but Andersen says that so far they have counted around 700 species and about half have never been recorded before.
Brassard is Canadian, and has studied ants in the USA and in Macau and Hong Kong. He was skeptical that Australia could top the Amazon for ant species, but not anymore.
“In Canada, we have about 100 species of ants,” he says. “ But we will find so many in just a few acres around here. The sheer diversity is unreal. It just seems like there are new things everywhere.”
Ants are often collected using pitfall traps – a shallow plastic bowl dug a few centimeters into the ground that contains a preservative. Andersen uses ethylene glycol, better known as antifreeze.
His record is 27 species in a 4.5 cm wide trap left out for two days in Kakadu National Park in the Northern Territory.
It is a measure of the large number of ants in the country.
“People wouldn’t even notice them despite the fact that they are incredibly numerous around Australia,” he says. “You can have dozens of colonies in an area that’s only 10 by 10 meters.”
Ants play a critical role in ecosystems. They both create and turn soil, they spread seeds, some defend plants, and they are all food for other animals.
If you could weigh all the world’s land-based fauna, Andersen says, about 20% of the mass would be taken up by ants.
“They are serious creatures in our environment,” he says. They recover weapon nutrients. They play an incredibly important role in the flow of energy and nutrients through ecosystems. It’s ants down there running the show.”
A 400-year taxonomic challenge
Andersen started collecting ants 40 years ago, and his collection – and that of many others – is housed at CSIRO’s laboratory in Darwin.
Even among these ants – almost all of which are unique to Australia – only 1,500 have been formally named by taxonomists. The collection is one of the largest on the planet.
When researchers like Andersen use new techniques to discover the true diversity among organisms, it creates a major challenge for taxonomists – the scientists who painstakingly describe new species and then publish the details in journals.
Prof Andy Austin is Director of Taxonomy Australia. He says hyper-diverse groups of fauna – like ants – are ushering in a quiet revolution for the profession.
Traditional methods of preparing detailed descriptions, drawings and creating flowcharts, known as keys, to identify one species from another are impractical when new scientific methods offer thousands and thousands of new candidates.
“You can’t continue with traditional taxonomy that was developed a hundred years or more ago,” he says.
Austin himself described around 650 new species – mostly wasps – but that took up most of his 40-year career.
“For Australia, we describe about 1,200 species a year of all organisms. It would take you 400 years to complete all of Australia’s biota, and that’s unacceptable for so many reasons.”
He says the new breed of taxonomists is using new techniques, such as describing new species using imaging and genetic data that is automated. It puts 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 actually exists on the continent,” he says.
As climate change and land clearing continue, “there will likely be species that die out before we get a chance to document them”.