Tiny creature undergoes massive change after humans arrive on island

The discovery has given researchers hope that some native creatures are able to adapt to humans.

A river in New Zealand with cleared land to the right, and remnant forest to the left.
New Zealand underwent rapid deforestation after European settlement, potentially causing many species to change and adapt. Source: Michael Dahlstrom

European settlement has had a clear impact on a species of native bug, new research has revealed. The dark-coloured long-tailed stonefly (Zelandoperla) that once lived in forests in New Zealand has vanished as its habitat has been destroyed, and its light-coloured cousin has moved in.

The reason behind the change is a surprising but simple one. The colouring of the darker version evolved to resemble a similar bug — the poisonous stonefly (Austroperla) — and this effectively tricked birds into thinking it was dangerous to eat.

“But the removal of forests since humans arrived has removed the poisonous species. As a result, in deforested regions the mimicking species has abandoned this strategy – as there is nothing to mimic – instead evolving into a different colour,” study co-author University of Otago Professor Jon Waters said.

With the loss of the poisonous sandfly, the dark-coloured long-tailed stonefly lost its advantage. And the light-coloured long-tailed stonefly, which can breed more successfully, took its place.

"The findings illustrate how humans have changed the ways in which our native species interact, disrupting adaptations that had co-evolved over millions of years," Waters added.

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Three insects on a leaf. The Austroperla (left), the dark-coloured zelandoperla (middle) and light-coloured zelandoperla (right).
Inside forests, the poisonous austroperla (left) is the subject of mimicry by the dark-coloured zelandoperla (middle). But it is replaced by light-coloured zelandoperla (right) when habitat is cleared. Source: Professor Jonathan Waters/Dr Graham McCulloch

Study co-author Dr Graham McCulloch and his team waded through streams, meticulously studying 1,200 stoneflies as part of their research. He told Yahoo News he expects finding more examples of changing wildlife is “just a matter of looking”.

“I suspect there will be changes like this happening everywhere, but you’ve just got to look and know where to look to understand it,” he said.

Similar examples have already been discovered in other countries. The most famous are likely the United Kingdom’s white-coloured moths which began to vanish as pollution from industrialisation in the 1800s killed lichens and blacked walls and tree trunks.

In Australia, it’s theorised that white-coloured magpies and kookaburras with a leucistic mutation can survive in suburbia because they blend in with white-coloured human infrastructure. While in forests, they would stand out against the foliage, and be targeted by predators which are more numerous in the wild than in cities.

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Land on New Zealand's North Island cleared for forestry.
After European settlement, New Zealand was cleared for forestry and agriculture. Source: Michael Dahlstrom

It’s not just the colour of the long-tailed stonefly that’s been impacted, the University of Otago research team has documented a second physical change. They lose their wings.

“When you're outside the forest, there's actually no advantage in having wings. That’s because it's very windy, and if you've got wings you’ll get blown away,” McCulloch said.

He believes the research is important because it shows native species can sometimes evolve to survive rapid change caused by humans.

“The other thing we're working on at the moment is what happens when you bring the forest back. In Aotearoa (NZ), there's a lot of reforestation happening. So we’re researching if these insects, can then regain their colour, which is extremely exciting,” he said.

The research has been published in the journal Science.

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