Birgit Rhode, Landcare Research

This 2mm beetle species evolved here 40 million years ago and survived the Oligocene mass extinction 23m years ago.

New Zealand science has exactly one specimen of a beetle that evolved here 40 million years ago.

Called Tatakiteana marskeae, it is known only from one mountainsidein Oparara, north of Karamea on the West Coast. It's of "very high conservation concern", says Dr Thomas Buckley of Manaaki Whenua Landcare Research.

It probably lived mostly in leaf litter or deadwood and the specimen is slightly longer than 2 millimetres.

It's not a fossil. It was collected in 2007 anddescribed and named in 2018.

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Buckley and colleagues recently studied this beetle and 764 other individual beetles using sophisticated DNA analysistechniques. They identified 15-20 lineages of zopherid beetles that were living on Zealandia about 23 million years ago.

Between three and 11 of these lineages probably date back to when the continent of Zealandia separated from Gondwana about 82myears ago.

Buckley was mostly interested in which beetle lineages were alive 23myears ago because that's the peak of the Oligocene Drowning.

The drowning was caused by the sinking of the New Zealand landmass and some geologists have proposed that all of Zealandia was underwater for probablysome millionsof years.

If that happened, then no Gondwanaspecies survived on land and every living thing on these islands are more recent arrivals.

But since the drowning proposal was made more than 25 years ago, DNA sequencing was developed and biologists have shown that many species on New Zealand today probably had ancestors that survived the Oligocene Drowning and a smaller group whose ancestors were alive on Gondwana.

These include various types of tuatara, frogs, wrens, crayfish, centipedes, weta, dragonflies, velvet worms, freshwater mussels and other shellfish, as well as 10 lineages of spider-like mite harvestmen.

Some trees mountain rimu and cypress as well as the native shrub griselinia and liverwort have also been traced back to Gondwana.

Today, it's thought that the land area of New Zealand was reduced to about 18 per cent of its current size by the Oligocene Drowning more than enough land for some species to survive but also causing the extinction of many others.

All of these ancient lineages must have beenrobust because they survived highglobal temperatures and high seas, as well as existingthrough many ice ages and numerous volcanic periods. They also survived the events 65myears ago that wiped out the dinosaurs.

"We find no evidence of an Oligocene mass extinction event" for these beetles, the authors concluded.

Zopherid beetles in New Zealand are notably diverse compared to overseas cousins and that adds to their interest for biologists, Buckley said.

About 190 NZ species have been described and there are probably many more undiscovered.

Some species don't have hindwings, meaning they can't fly. If their ancestors couldn't fly, then surviving the numerous environmental changes would have been more difficult and making their survival more remarkable.

Dating a species back millions of years depends on DNA sequencing, fossil and other calibrations, as well as statistical analysis.

The techniques left Buckley and colleagues with some uncertainty. Only one of the two calibration models showed lineages dating back to Gondwana for example. And the broad range of speciesidentified as that old (three to 11) illustrates the current limits of the science.

These uncertainties have been used by other scientiststo argue that a total drowning occurred during theOligocene.

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Hardy beetles survived all that Zealandia threw at them for 40 million years - Stuff.co.nz