How songbirds island-hopped their way from Australia to spread their wings across the world
The songbirds that are
common in gardens all across the world have a surprisingly distant origin. They
all evolved from a common ancestor that emerged from what is now Australia
around 24m years ago. How they managed to leave this isolated part of the world
and spread all over the planet has long been a mystery to scientists. But a new
study suggests they began spreading just as the islands in and around Indonesia
were being formed, creating a pathway for them to cross what had previously
been thousands of kilometres of open ocean.
Songbirds are a
tremendously diverse group of small perching birds,
made up of over 5,000 known species distributed across the world. Common
examples include the European robin (Erithacus
rubecula) and the North American song sparrow (Melospiza
melodia). Together, songbirds account for almost half of all bird species
alive today.
Although fossils of birds are rare,
the ancestor of all songbirds is thought to have originated
in Australia, at a time when the Australian landmass was separated from all
other land by a vast ocean in all directions. So, despite the birds' extensive
evolutionary spread, it remained unclear how this diverse and cosmopolitan
family arose from a single ancestral species on an isolated continent.
However, a recent study by
researchers at the University of Kansas and published in the journal Nature
Communications sheds new light on this question. Using genetic and fossil data,
the authors reconstructed the evolutionary “family tree” for songbirds. They
then linked this to information on different species’ geographic locations to
understand how early songbirds spread between different continents over the
course of millions of years.
This confirmed that
songbirds originated in Australia just over 30m years ago. But the most
eye-catching finding is that songbirds started to spread out of Australia much
more recently than previously thought. This process appears to have started
approximately 24m years ago, at the same time as the formation of Wallacea, a
group of islands bridging the ocean-filled gap between Australia and Asia. So this
may explain how songbirds were able to leave Australia and radiate across the
rest of the world, by island-hopping their way to Asia… read more:
