Researchers say 'tree of life' actually a 'bush'

The idea is that when incidents of rapid speciation arise, evolution moves so quickly that the genome doesn't diverge neatly.
By Brooks Hays  |  Aug. 18, 2015 at 6:14 PM
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UPPSALA, Sweden, Aug. 18 (UPI) -- The array of lineages that make up the kingdoms of the biological world are often represented and referred to as "the tree of life" -- each species a branch.

But a new study suggests genealogy is more complicated than a branching tree.

Recently, scientists at Sweden's Uppsala University analyzed the genomic lineages of some 50 bird species using a new statistical method based on the phenomenon of "jumping genes" and "incomplete lineage sorting."

The idea is that when incidents of rapid speciation arise, evolution moves so quickly that the genome doesn't diverge neatly but is haphazardly dispersed.

"We can see that the very rapid rate at which various bird species started evolving once the dinosaurs went extinct, i.e. around 65 million years ago, meant that the genome failed to split into separate lineages during the process of speciation," researcher Hans Ellegren explained in a press release.

Ellegren is the lead author of a new paper on the subject, published in the journal PLOS Biology.

"Previously, the difficulty resided in finding instances of incomplete lineage sorting far back in time," Ellegren added. "Therefore, it's been unknown if this phenomenon has affected evolution to any appreciable extent."

The sporadic transposal of genes can complicate the relations among different species. The new analysis, for example, reveals part of a cuckoo's genome to be more closely related to a hummingbird than a pigeon, while the opposite is true of another portion.

"The more complex kinship patterns that result from this phenomenon mean that the 'tree of life' should often be understood as a 'bush o life,'" the researchers say.

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