Mystery solved: When butterflies evolved and what plants they used for food

A significant event transpired about 100 million years ago: a faction of innovative moths began to fly during the day, as opposed to night, favoring the nectar-laden flowers that had evolved alongside bees. This singular event sparked the evolution of butterflies, a fascinating transformation that scientists have been studying for decades.

In 2019, scientists were able to pinpoint the timing of this evolution through a comprehensive DNA analysis. This groundbreaking research debunked the previously held theory that butterflies evolved due to pressure from bats, following the extinction of dinosaurs.

Today, scientists have unearthed new exciting revelations concerning the geographical origins of the first butterflies and their dietary preferences.

How the discovery was made

This discovery was not easy to come by. It necessitated the collaborative efforts of researchers from across the globe, who worked tirelessly to construct the world’s most extensive butterfly tree of life. This complex structure comprised DNA from over 2,000 butterfly species, representing every butterfly family and 92 percent of all genera.

The researchers utilized this tree as a roadmap, tracing the butterflies’ journey and dietary patterns through time, a monumental task akin to solving a four-dimensional puzzle. The puzzle’s solution pointed to North and Central America as the origin of the first butterflies, a finding recently published in the journal Nature Ecology and Evolution.

For Akito Kawahara, the lead author of the study and the curator of lepidoptera at the Florida Museum of Natural History, this project was the culmination of a lifelong dream.

“This was a childhood dream of mine,” said Kawahara. “It’s something I’ve wanted to do since visiting the American Museum of Natural History when I was a kid and seeing a picture of a butterfly phylogeny taped to a curator’s door. It’s also the most difficult study I’ve ever been a part of, and it took a massive effort from people all over the world to complete.”

How to trim down a 100-million-year history from 19,000 species

The study’s enormity is reflected in the sheer number of butterfly species – about 19,000. Stitching together their 100 million-year history required a deep understanding of their modern distributions and host plants. Unfortunately, before this study, such data was not readily available in one location.

“We often had to rely on field guides that hadn’t been digitized and were written in various languages,” Kawahara explained.

The lack of an existing database did not deter the researchers. They embarked on the painstaking process of creating a publicly accessible database, translating and digitizing information from books, museum collections, and scattered web pages.

A crucial component of their analysis was 11 rare butterfly fossils. These fossils, preserved despite the delicate nature of butterfly wings and fine hairs, served as calibration points on the genetic trees. They enabled the researchers to record the timing of key evolutionary events.

What the researchers learned

The results revealed a dynamic narrative of rapid diversifications, intermittent advancements, and unlikely dispersals. Some butterfly groups covered vast distances, while others remained stationary, seemingly indifferent to the shifting continents, mountains, and rivers around them.

The first butterflies, the study found, appeared in Central and western North America. During this period, North America was split in two by a vast seaway, and Mexico was connected in a long arc with the United States, Canada, and Russia. The Isthmus of Panama had not yet joined North and South America, but butterflies managed to cross the strait between them with ease.

The migration pattern of butterflies was intriguing. Despite the relative proximity of South America and Africa, butterflies took a circuitous route, journeying to Asia across the Bering Land Bridge. Once there, they rapidly dispersed, spreading into Southeast Asia, the Middle East, and the Horn of Africa. Incredibly, they also reached India, which was then an isolated island surrounded by miles of sea.

Their arrival in Australia, which was still connected to Antarctica, the last remnants of the supercontinent Pangaea, was even more astounding. It’s plausible that butterflies thrived in Antarctica when global temperatures were warmer, traversing the northern edge of the continent into Australia before the landmasses eventually separated.

Interestingly, butterflies lingered on the outskirts of western Asia for nearly 45 million years before finally venturing into Europe. The cause of this extended pause remains unclear, but its effects are still visible today.

“Europe doesn’t have many butterfly species compared to other parts of the world, and the ones it does have can often be found elsewhere,” explained Kawahara. “Many butterflies in Europe are also found in Siberia and Asia, for example.”

Butterfly species diversification begins

Once butterflies had established themselves, they diversified rapidly alongside their plant hosts. By the time the dinosaurs met their end 66 million years ago, almost all modern butterfly families had emerged. Each family seemed to have a specific preference for certain groups of plants.

“When we looked at this association over an evolutionary timescale, we found that in pretty much every family of butterflies, bean plants appeared to be the ancestral hosts,” Kawahara said. “This was true for the ancestor of all butterflies as well.”

While bean plants have since broadened their pollinators to include various bees, flies, hummingbirds, and mammals, butterflies have also diversified their tastes.

Study co-author Pamela Soltis, a Florida Museum curator and distinguished professor, points out that the symbiotic relationships butterflies developed with plants were instrumental in their evolution from a minor moth offshoot to one of the largest insect groups on Earth.

“The evolution of butterflies and flowering plants has been inexorably intertwined since the origin of the former, and the close relationship between them has resulted in remarkable diversification events in both lineages,” she stated.

This intricate, vibrant history of butterflies demonstrates the profound interconnectedness of life on Earth, the perpetual dance of evolution and adaptation, and the mystery that continues to envelop the natural world. 

The study underscores the importance of cross-disciplinary and international collaboration in expanding our knowledge about the origin and evolution of species. The journey of these tiny creatures over millions of years offers invaluable insights into the dynamism and resilience of life, and the ongoing saga of evolution.

More about butterflies

Butterflies are much more than just beautiful creatures that flutter around our gardens. They play several essential roles in ecosystems and contribute significantly to the overall health of the environment.

Pollination

Like bees, butterflies are important pollinators. As they move from flower to flower in search of nectar, they inadvertently pick up and transfer pollen grains. This cross-pollination is crucial for the fertilization and propagation of many plant species, including those that humans depend on for food.

Bioindicators

Butterflies are considered sensitive bioindicators, meaning their presence, absence, or population trends can tell us a lot about the health of an ecosystem. Because butterflies are highly sensitive to changes in habitat quality and climate, a decline in butterfly populations can serve as an early warning sign of environmental problems.

Biodiversity

Butterflies contribute to biodiversity both as pollinators and as a food source for other species. Their caterpillars are a primary food source for birds and some insects. A healthy butterfly population can indicate overall biodiversity and ecosystem health.

Nutrient Recycling

Butterfly larvae (caterpillars) play a role in nutrient recycling. They consume plant leaves, aiding in the decomposition process and contributing to the nutrient cycle. When they metamorphose into butterflies, their discarded pupal cases provide nutrients for the soil.

Plant Growth and Evolution

Some butterfly species have co-evolved with specific plant species, leading to mutual benefits. For example, the plant may rely on the butterfly for pollination, while the butterfly relies on the plant as a food source for its larvae. This relationship can drive the evolution of both species.

Human Wellbeing

The aesthetic value of butterflies also contributes to human wellbeing. Their beauty encourages people to spend time outdoors, engage with nature, and appreciate biodiversity, which has numerous mental health benefits.

Education and Research

Butterflies, due to their wide variety, availability, and the fascinating process of metamorphosis they undergo, serve as excellent subjects for educational purposes and scientific research. Observing butterflies can provide insights into biological processes like metamorphosis, behavior, and ecological interactions.

However, it’s essential to note that butterfly populations are declining globally due to habitat loss, climate change, pollution, and the use of pesticides. 

The loss of these creatures can have cascading effects on ecosystems and biodiversity, underscoring the need for conservation efforts. Protecting and restoring butterfly habitats, reducing pesticide use, and planting butterfly-friendly plants can all help to support butterfly populations.

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