Despite being studied intensely, the evolutionary history of butterflies is not well understood. Credit: Subhra Priyadarshini

A genomic study reveals that butterflies originated in what is present-day western North America or Central America1. The insects evolved around 100 million years ago after flowering plants originated.

Despite being the most intensely studied insect group, the evolutionary history and diversity of butterflies are not well understood. An international research team sequenced 391 genes from nearly 2,300 butterfly species, sampled from 90 countries and 28 specimen collections to get more insights.

The team, which included a researcher at the National Centre for Biological Sciences in Bengaluru, created a new phylogenetic tree of butterflies representing 92% of all genera. They found that butterflies originated from nocturnal, herbivorous moth ancestors.

Analysis indicated that butterflies dispersed from the Americas to tropics via Beringia, an arctic landscape, around 75 million years ago. Over the course of evolution, butterfly speciation was much higher in the tropics than in temperate zones.

Around 17 million years ago, butterflies colonised Europe and were present on what are now modern continents.

The researchers found that more than two-thirds of living butterfly species feed on a single plant family; whereas less than a third feed on two or more. The insects feed mainly on grasses and legumes, two geographically widespread plant families that lack potent defensive chemicals. This trait may have allowed butterflies to remain associated with these plants for millions of years.

The molecular, host plant and geographic data in this study provide a baseline for future comparative analyses of butterflies, the researchers note.