How mountains Influence bird evolution

Around 85 percent of the world’s vertebrates, including birds, live in mountainous areas. The lowland habits between mountains keep the populations and species isolated from each other. For centuries, scientists have wondered, how do new species form in different mountain areas?

Some hypothesize that birds simply fly to other mountains, while others say they don’t often colonize other peaks. Researchers from the University of Copenhagen provide the first evidence of what happens, at least with birds living in the islands around Indonesia and Australia.

By collecting and analyzing genomes of various bird populations from the order Passeriformes in New Guinea, the scientists have learned that bird species emerge in the lowlands and then move up in elevation over time. They move higher over millions of years due to factors such as climate change and competition. Since most bird species exist for a few million years before going extinct, many species eventually die out while inhabiting mountainous areas.

“Our analyses demonstrate that the species living on mountain peaks are 5-10 million years old. So, the oldest and most specialized species live at elevations of 3-4 kilometers, and in small numbers. Climate fluctuations can accelerate the process, so that ancient species will go extinct faster. This will probably be a consequence of modern-day global warming as well,” explained study lead author Knud Andreas Jønsson of the Natural History Museum of Denmark

Moreover, as bird populations move higher, they become more distinct from other populations. Jønsson further explains,

“We can see that the higher up in the mountains birds live, the greater the differences between populations of the same species,” said Jønsson. “Some of the populations are so different, that one could make the case that they are distinct species. Conversely, there are greater similarities among lowland populations. This tells us that the spread of new species must have taken place from lowland habitats upwards.”

This information is vital to conservationists. Currently, most conservation efforts in the region focus on lowland forests, and for a good reason. A large amount of these forests have disappeared, and with them, birds and many other animals. However, knowing that some of the longest-lived and genetically varied species live in the highlands, we should consider focusing conservation efforts there, especially since they are more vulnerable to global warming. 

The study, “The formation of avian montane diversity across barriers and along elevational gradients,” is published in Nature Communications.

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By Erin Moody , Earth.com Staff Writer