Songbirds may have 'borrowed' DNA to fuel migration

September 20, 2013
This is an Audubon's warbler. Credit: David Toews, UBC

A common songbird may have acquired genes from fellow migrating birds in order to travel greater distances, according to a University of British Columbia study published this week in the journal Evolution.

While most birds either migrate or remain resident in one region, the Audubon's warbler, with habitat ranging from the Pacific Northwest to Mexico, exhibits different behaviours in different locations. The northern populations breed and migrate south for the winter, while southern populations have a tendency to stay put all year long.

Evolutionary biologists have long been puzzled by research that indicates some Audubon's warblers share the same mitochondrial DNA (mtDNA) with myrtle warblers – a different species of songbird that migrates annually to the southeastern U.S., Central America and the Caribbean – even though they look dramatically different.

"Mitochondria are only passed down from mothers to their offspring," says David Toews, a PhD candidate in UBC's Department of Zoology. "So it's a very useful marker for differentiating species. In this case, finding two species of songbirds sharing the same mtDNA is very surprising, so we set out to find out why."

This is a map showing the breeding ranges, migratory behavior and distribution of mitochondrial DNA (mtDNA) in four groups of yellow-rumped warblers. New data from Toews and colleagues demonstrates that the area where there is a transition in mtDNA is also home to a shift in migratory behavior, from residents to migrants. Credit: Toews, et al. UBC.

By analyzing genetic data and in feathers, and by measuring of the mitochondria in their flight muscles, Toews and fellow researcher Milica Mandic pinpointed the precise geographical location near the Utah-Arizona border where the myrtle warblers' "wanderlust" genes displace the Audubon warbler's ancestral mitochondria. This region happens to also be the transition zone where we see a change in the of Audubon's warblers.

"Because of its prominent role in reconstructing , people often forget that mitochondria actually have a very important function as the main energy generator of cells," says Toews. "Our findings suggest that over generations, the Audubon's warbler may have co-opted the myrtle's mitochondria to better power its own travels."

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1 / 5 (7) Sep 21, 2013
Interbreeding or horizontal gene transfer mediated by a virus?
5 / 5 (1) Sep 21, 2013
I never read of a virus either packing a whole mitochondrium into its envelope, or even mitochondrial DNA. So I think the odds are in favour of interbreeding.
1 / 5 (6) Sep 21, 2013
Agreed, but it is possible.

3.7 / 5 (3) Sep 22, 2013
@Chromodynamix - Um, no it isn't. That would imply a virus packing in its tiny payload the entire genome of a true cellular organism. Viruses don't have the capability of self-reproduction. Even if they had the genome entire, they could do nothing with it to aid their own reproduction.

Think of a virus like a terrorist who takes over another factory that normally makes something useful and co-opts it to make more guns to take over more factories. It can't build a factory out of guns. It can't hire guns to run the factory even if it could build one out of guns. It is a really focused overblown enzyme, and not much more. It can't do anything like what apparently is being attributed to it by you.

1 / 5 (5) Sep 23, 2013
There are some pretty big viruses around, and horizontal gene transfer often involves temperate bacteriophages and plasmids.
At Edinburgh we were using P4 phage viruses to transer bits of genetic material from one strain of Salmonella to another.
3.3 / 5 (3) Sep 23, 2013
Key word being "bits" not "entire genomic sequences and somehow managing at the same time to supplant entire the genomic sequence of the subsequent host."
2 / 5 (3) Oct 02, 2013
cute bird

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