Asian Scientist (Jul. 18, 2013) – An international team of researchers has decoded the genome of the ground tit (Parus humilis), revealing the genetic secrets of how this small bird can survive in one of the most hostile environments on earth.
The ground tit lives in the Tibetan plateau, the largest high-altitude land mass in the world. In their study, published in Nature Communications, the scientists found molecular clues in the ground tit genome which may explain how it copes with the extreme living conditions of this habitat.
“We have long known that these birds are well adapted to living with low oxygen levels, typical of high elevation, but until now we have had only a limited understanding of the genetic background of these adaptations,” said Dr Sankar Subramanian, a member of the team.
“In this study we have identified the genetic modifications of the species which make this possible.”
Unlike its tree-dwelling relatives, the drab-coloured little songbird lives exclusively above the tree line at 3,300 to 5,400 meters, on rocky steppes and grasslands of the Tibetan plateau.
As a consequence of its location, it also behaves differently by foraging on the ground and digging burrows or tunnels for roosting and nesting. It looks different too with a longer, straighter bill, longer legs, larger body size and paler overall plumage.
Because of all these divergent characteristics, the ground tit was long considered to belong to the crow family. However, rather than being the world’s smallest corvid, it was later identified as the world’s largest tit.
“Our genomic study further confirms this taxonomic conclusion. The ancestor of the ground tit split off from other tits between 7.7 and 9.9 million years ago,” said Dr Subramanian.
The study also revealed how the ground tit genome can be characterized by a range of adaptations to the environment it calls home.
This includes positive selection for genes involved in hypoxia response (necessary for low oxygen environments) and skeletal development. Such adaptations can also be found in other organisms living in similar high-altitude environments.
The researchers also found an expansion of genes involved in fatty acid metabolism in the ground tit genome. According to the researchers, this may help the ground tit withstand extreme cold in its environment.
One surprising adaptation was the apparent loss of genes that provide immunity against pathogens, including viruses and bacteria.
“It is possible that this is because there are fewer microorganisms present in the Tibetan plateau and therefore a decreased risk of opportunistic infections,” said Dr Subramanian.
Future research will focus on comparing genomes from closely related species inhabiting high altitudes and lowland environments to further explore the genetic foundation of adaptations necessary for a high-altitude environment.
The article can be found at: Qu et al. (2013) Ground Tit Genome Reveals Avian Adaptation To Living At High Altitudes In The Tibetan Plateau.
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Source: Griffith University; Photo: ninjawil/Flickr.
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