On the Himalayan-enveloped Tibetan Plateau
and the Altiplano plateau of South America – the world's two highest tabletops
– a select few bird species survive on 35 to 40 percent less oxygen than at sea
level.
All extreme-altitude birds have evolved especially efficient systems for delivering
that precious oxygen to
their tissues. But a new study led by the University of Nebraska-Lincoln and
Chinese Academy of Sciences has found that these birds often evolved different
blueprints for assembling the proteins – hemoglobins – that actually capture
oxygen.
Published in the Proceedings of the
National Academy of Sciences, the study found that many species from the two
plateaus underwent different mutations to produce the same result: hemoglobins
more adept at snaring oxygen from the lungs before sharing it with the other
organs that depend on it.
Those mutational differences often emerged
even among closely related species residing on the same plateau, the study reported.
"You could imagine, just because of the
different ancestral starting points, that the Tibetan birds maybe all went one
(mutational) route, and the Andean birds typically did things a different
way," said co-author Jay Storz, Susan J. Rosowski Professor of Biological
Sciences at Nebraska. "But that's not what we saw. Across the board, there
weren't really any region-specific patterns.
"In both cases, it seems like there were
many different ways of evolving a similar alteration of protein function."
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