Scientists have long suspected that P. atlantica carries more chromosomes than other non-polyploid animals (those with no more than two sets of chromosomes), but they had never sequenced the genome of this elusive butterfly species—until now.

“When we set out to start to understand evolution in butterflies, we knew we had to sequence the most extreme, and somewhat mysterious, Atlas blue butterfly,” said Charlotte Wright, an evolutionary biologist at the Wellcome Sanger Institute in a statement.

In a recent study, Wright and her colleagues discovered that P. atlantica boasts a whopping 229 pairs of chromosomes, and this sizable genome likely resulted from its ancestor’s chromosomes fragmenting into small pieces, rather than duplicating.1

The researchers also found that these events of genome fragmentation, also known as fission, likely occurred in the more loosely packed and transcriptionally active parts of the chromosome. Their findings, published in Current Biology, shed light on how the Atlas blue butterfly evolved and provide hints on how it may adapt in the future.
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According to Vila, the extent of P. atlantica’s genome fragmentation suggests that there are evolutionary reasons for this process, and scientists can now begin to explore them. Wright agreed, “We can start to investigate what benefits [fission] might have, how it impacts [the Atlas blue butterflies’] ability to adapt to their environment, and whether there are any lessons we can learn from their DNA that might aid conservation in the future.”