Going up: Birds and mammals evolve faster if their home is rising

Date:
September 2, 2021
Source:
University of Cambridge
Summary:
The rise and fall of Earth's land surface over the last three
million years shaped the evolution of birds and mammals, a new
study has found, with new species evolving at higher rates where
the land has risen most.



FULL STORY ==========================================================================
The rise and fall of Earth's land surface over the last three million
years shaped the evolution of birds and mammals, a new study has found,
with new species evolving at higher rates where the land has risen most.


========================================================================== Researchers at the University of Cambridge have combined reconstructions
of the Earth's changing surface elevations over the past three million
years with data on climate change over this timeframe, and with bird
and mammal species' locations. Their results reveal how species evolved
into new ones as land elevation changed -- and disentangle the effects
of elevation from the effects of climate.

The study found that the effect of elevation increase is greater than
that of historical climate change, and of present-day elevation and temperature, in driving the formation of new species -- 'or speciation'.

In contrast to areas where land elevation is increasing, elevation
loss was not found to be an important predictor of where speciation
happens. Instead, present-day temperature is a better indicator of
speciation in these areas.

The results are published today in the journal Nature Ecology and
Evolution.

"Often at the tops of mountains there are many more unique species that
aren't found elsewhere. 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 Dr Andrew Tanentzap in the University of Cambridge's Department of Plant Sciences, senior author
of the paper.

As land elevation increases, temperature generally decreases and habitat complexity increases. In some cases, for example where mountains form, increasing elevation creates a barrier that prevents species moving and
mixing, so populations become reproductively isolated. This is the first
step towards the formation of new species.

The effect of increasing elevation on that rate of new species formation
over time was more pronounced for mammals than for birds; the researchers
think this is because birds can fly across barriers to find mates in other areas. Birds were affected more by present-day temperatures; in birds, variation in temperature creates differences in the timing and extent
of mating, risking reproductive isolation from populations of the same
species elsewhere.

Until now, most large-scale studies into the importance of topography in generating new species have only considered present-day land elevation,
or elevation changes in specific mountain ranges.

"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. The
rate at which species evolved in different places on Earth is tightly
linked to topography changes over millions of years," said Dr Javier
Igea in the University of Cambridge's Department of Plant Sciences,
first author of the paper.

He added: "This work highlights important arenas for evolution to
play out.

From a conservation perspective these are the places we might want
to protect, especially given climate change. Although climate change
is happening over decades, not millions of years, our study points
to areas that can harbour species with greater potential to evolve."
The researchers say that as the Earth's surface continues to rise and
fall, topography will remain an important driver of evolutionary change.

========================================================================== Story Source: Materials provided by University_of_Cambridge. The original
text of this story is licensed under a Creative_Commons_License. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Igea, J., Tanentzap, A.J. Global topographic uplift has elevated
speciation in mammals and birds over the last 3 million years. Nat
Ecol Evol, 2021 DOI: 10.1038/s41559-021-01545-6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210902124919.htm

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