Rare study of a common Australian robin has global implications for genome evolution and local climate adaptation

Research into how powerhouse genes evolve and form partnerships is critical for understanding how organisms adapt their metabolism to local climates, but rare.

Most complex organisms have two independent genomes - nuclear and mitochondrial - in every cell. These two genomes have a partnership dating back 1.45 billion years - together they run the most important metabolic functions of the cell, converting nutrients into energy.

While it has long been known that this partnership is essential to life for complex organisms, its role in adaptation to local conditions is less well understood.

Now the well-loved Australian Eastern yellow robin has taken centre stage and proven itself an excellent natural study system for testing major new ideas concerned with how species evolve to suit different climates.

A common and widespread, well-loved Australian bird has proven itself one of the best natural study systems in which to explore major new ideas about how species evolve to suit different climates, and how that might cause the emergence of new species. Photo Credit: Chris Tzaros

A study published today in Nature Ecology and Evolution, led by Monash scientists from the School of Biological Sciences, indicates that co-operative evolution between the two kinds of genome has occurred twice in a common bird species.

“By discovering a special nuclear gene region that seems to act as a ‘supergene’ enabling

mitochondrial and nuclear co-operation, we have indicated novel means by which Eastern yellow robins may have been able to differentiate into two types adapted to different local climates”, said lead author Dr Hernan Morales, now a post-doctoral researcher at the University of Gothenburg.

The research team genetically sampled Eastern yellow robins with contrasting mitochondrial genetic types along two independent sampling lines, across different climates and hundreds of kilometres apart.

The robins were released after providing a small blood sample.  For each bird the researchers obtained the DNA sequences of more than 60,000 gene regions with and without known roles in mitochondrial function, to test how nuclear genetic variation relates to that in the mitochondrial genome.

Study lead author Professor Paul Sunnucks, said the research was significant because it shows that, in a wildlife species, strong differences in mitochondrial genotypes are mirrored by nuclear regions that drive mitochondrial functions, even though most of the nuclear genome is very similar.

“These genes are packaged into a very unusual region of the genome whose characteristics provide us with a candidate explanation for how the many nuclear genes with mitochondrial functions may be able to maintain evolutionary partnerships with the far fewer genes of the mitochondrial DNA, forming blueprints for different metabolisms in different climates,” Professor Sunnucks said.

“Importantly, the genetic feature we have discovered in this bird may be available to many bird species, providing a previously unrecognized avenue for evolution of mitochondrial and nuclear interactions,” said co-author Dr Sasha Alexandra Pavlova, who is leading related studies into additional species.

The full article can be read here.


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