Scientists make intriguing discovery after conducting experiments with butterflies: 'Essential for predicting the future'

The wall brown butterfly in Europe could be hitting a northern limit to its range expansion despite rapid adaptations to warming temperatures, according to a report by Stockholm University posted by Phys.org.

What's happening?

Researchers from Sweden found that butterflies can quickly adjust their life cycles when moving to new northern areas, but winter cold still blocks them from living beyond certain boundaries.

The scientists conducted field experiments over two years, moving butterflies from southern and northern Sweden to test locations that included spots where the species doesn't exist.

The wall brown has become more common at higher latitudes in Scandinavia in recent decades, while numbers have dropped in Western Europe. Researchers put butterflies in field cages at different sites and watched how caterpillars grew.

"We wanted to know whether traits like faster growth, properly timed winter dormancy, and improved winter survival have evolved in northern butterflies," said Karl Gotthard, professor at Stockholm University's Department of Zoology.

Results showed that northern butterfly groups had evolved to grow faster than southern ones, a change that likely helps with shorter summers at higher latitudes. They also got their winter dormancy timing right. Despite these changes, almost no caterpillars lived through winter in Dalarna, north of where the species currently lives.

Why is knowledge of butterfly adaptation important?

Knowing evolutionary boundaries helps scientists forecast how wildlife will respond to our warming planet — and whether there could be limits to pollinators such as butterflies (which can be important to humans for agriculture) as well as to pests that spread disease.

While many species move northward as temperatures climb, this study shows that evolution alone can't beat all climate obstacles.

"Our results show that even though the butterflies adapt their life cycle as they move northward, there are limits that evolution cannot easily overcome," explained Mats Ittonen, lead author from Stockholm University.

For the wall brown, moving farther north will still require winters to get warmer, not just summers to get warmer and longer, per the university report. The researchers suggested that limits could hold true for other species, including not only beneficial pollinators such as butterflies but also potential pests and disease carriers that might spread to new areas.

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"Understanding both which traits evolve and which ones actually set the limits for where species can live is essential for predicting the future of ecosystems and biodiversity in a warming world," said Ittonen.

What can I do to help butterflies and pollinators?

You can plant native wildflowers in your yard or community spaces to help butterfly populations. These plants provide food for caterpillars and nectar for adult butterflies, giving them the resources they need to settle in new areas.

Cut light pollution in your neighborhood to help pollinators keep their natural life cycles. Turn off outdoor lights when not in use to create darker conditions that many species require for proper growth.

Support habitat conservation groups that protect the ecosystems that butterflies need to thrive. Donations to these organizations fund research and land protection efforts that give butterflies and other pollinators the best chance to adjust to our warming world.

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