When land rises, bird and mammal evolution speeds up

Over the last 3 million years, bird and mammal species have evolved more rapidly in places where land has risen more dramatically -- according to a new research.

The study, published Thursday in the journal Nature Ecology and Evolution, is one of the first to investigate the links between elevation change and speciation on a global scale.

According to the analysis, land elevation increases have had a greater impact on speciation than historical climate change.

During the last few million years, colliding tectonic plates have pushed new mountain ranges higher and higher, as other plates drift apart and older mountain ranges are weathered and shrink.

Lands that experience increases in elevation tend to get cooler and more ecologically complex. These changes create new ecological niches for divergent species. Land elevation changes also yield geographical barriers, preventing species from mixing and allowing populations to become genetically distinct.

"Often at the tops of mountains there are many more unique species that aren't found elsewhere," senior study author Andrew Tanentzap said in a press release.

"Whereas previously the formation of new species was thought to be driven by climate, we've found that elevation change has a greater effect at a global scale," said Tanentzap, a scientist at the University of Cambridge.

For the study, scientists calculated global speciation rates over the last 3 million years. Researchers also plotted elevation changes across Earth's continents.

The analysis showed speciation rates were highest in places where elevation increases were greatest.

Conversely, the effects of erosion and land elevation decreases were less predictive of speciation rates. In areas where elevation decreased, temperature changes better explained differences in speciation rates.

Previous efforts to link elevation changes and speciation rates have mostly focused on specific mountain ranges and Earth's most recent geologic history, but the authors of the newest study took a more global approach.

"It's surprising just how much effect historical elevation change had on generating the world's biodiversity -- it has been much more important than traditionally studied variables like temperature," study first author Javier Igea said in a press release.

"The rate at which species evolved in different places on Earth is tightly linked to topography changes over millions of years," said Igea, also a researcher at the University of Cambridge.

The findings could have implications for conservation. Because birds and mammals in regions where land elevation is increasing could be more likely to yield new species, it might make sense to enact stronger protections.

Though the latest study relied on ancient fossil records for much of their analysis, the authors contend the rising and falling of Earth's land will continue to drive evolutionary change.

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