A new study suggests that the rise and fall of Earth's landscapes have also affected the evolution of animals, with birds and mammals in mountainous regions evolving quicker.
Researchers from the University of Cambridge suggest that the changes in the Earth's terrestrial surface over the last 3 million years have affected the evolution of animals, especially birds and mammals.
One particular mechanism at work is elevation being a significant driver of speciation, or the development of separate and new species, compared to other factors like temperature or long-term climate change.
Researchers presented their findings in the article "Global Topographic Uplift Has Elevated Speciation in Mammals and Birds Over the Last 3 Million Years," appearing in the Nature Ecology & Evolution journal, September 2.
Topographic Changes Driving Speciation in Birds, Mammals
Rising mountains and hills are some of the topographic changes that lead to "novel habitats and niches where new species evolve and diversify," according to the authors of the paper.
Cases in point include the kea, a large parrot endemic to the alpine regions of New Zealand, and the bighorn sheep found in the Rocky Mountains in the US. These are unique species that have evolved in mountainous regions.
"Often at the tops of mountains there are many more unique species that aren't found elsewhere," notes Dr. Andrew Tanentzap, senior author of the study and a member of Cambridge's Department of Plant Sciences, in a Daily Mail report.
"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," he added.
Researchers additionally noted that increasing elevation had a more profound effect on birds and mammals. For birds, researchers suggest that it might be because they can fly across barriers to find mates in other places, which makes the effect on them more pronounced than in mammals.
Dr. Tanentzap explains that as altitude increases, the environment changes, citing the work of Victorian-era naturalist Alexander von Humboldt's maps. These dated illustrations show the changes in habitats with changing land levels.
Another factor that leads to speciation is that natural barriers emerge, preventing animals from interbreeding as the land rises.
Visualizing Effect of Land Rise on Evolution
In their new study, researchers used reconstructions of the Earth's changing surface elevations from the last 3 million years. They integrated it with climate change data over the same period, together with known locations of mammal and bird species.
Their work revealed that with the increase in land levels, average temperatures start to drop, and habitat complexity starts to increase.
There are even instances where elevation creates a barrier that effectively prevents interaction and interbreeding between populations, isolating them and leading them down different evolutionary tracks - a case often observed in mountain formations.
In the kea, for example, the temperature change also creates a change in timing and mating patterns, risking reproductive isolation from other populations of the same species in other locations.
A 2008 article from the Heredity journal explains that reproductive isolation is an integral part of speciation, preventing two populations from interbreeding.
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