Animal Genomes Evolve Along One-Way 'Highways,' a Map of 4,454 Species Suggests

A study published Aug. 19 in Science Advances places more than 5,800 animal genomes on a single map and reports that chromosomes rearrange along a limited set of routes that cannot be retraced, according to the University of Vienna's release on the work.

The team analyzed more than 5,800 publicly available chromosome-scale genomes, spanning 4,454 species across 19 animal phyla, the release says; the caption on the study's map gives 5,821 genomes. Chromosome-scale assemblies place every gene in order along complete chromosomes, unlike the draft genomes that make up most of what has been sequenced. The researchers call their framework evolutionary genome topology.

At the center of the pattern is a process the same group named in earlier work, "fusion-with-mixing": when two chromosomes fuse, their genes intermingle in a way that cannot be undone, leaving a permanent record of the event. Differences in chromosome number across animal groups arise either from ancestral chromosomes combining or from them separating, and in both cases, fusion-with-mixing sends lineages down different paths, per the release. Because the change runs only one way, it also works as a marker of shared ancestry.

"For the first time, we can see thousands of genomes on a single map and trace the unique paths along which animals' DNA evolved," said Darrin Schultz, who led the work as a postdoctoral researcher at the University of Vienna and is now an assistant professor at Lehigh University.

The university calls it "the largest such comparison across the animal tree of life to date," which is its own assessment of its own study. The release adds that some groups, among them mosquitoes, glass sponges, and earthworms, occupy isolated regions of the map with no close parallel, and that the framework could be used to simulate possible future directions of genome evolution.

All animals share a common ancestor that lived more than 600 million years ago, the release notes. Funding came from the European Research Council, the Austrian Science Fund, and the Rupert Riedl Prize of the Vienna Haus des Meeres Verein.