Overview

• Researchers at the Wellcome Sanger Institute and Barcelona’s Institute of Evolutionary Biology produced the first gold‑standard genome for Polyommatus atlantica, published in Current Biology.
• Hi‑C mapping shows 227 small, similarly sized autosomes plus two large sex chromosomes, consistent with extensive fragmentation rather than whole‑genome duplication.
• Fragmentation breakpoints are enriched in A compartments and depleted in B compartments, linking 3D chromatin state to where chromosomes split.
• Comparisons with the common blue butterfly support fission as the mechanism, with the karyotype inferred to have shifted from about 24 to 229 pairs over roughly three million years.
• The work opens avenues into how chromosome number shapes evolution and may inform cancer biology, as the Atlas blue’s mountain‑range populations face threats from warming, forest loss, and overgrazing.