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Last Updated: Friday, 28 January, 2005, 09:38 GMT
Bat evolution linked to warming
The Little Epauletted bat Epomorphorus minimus, photographed in Ethiopia     (Image: Paul Bates)
Bats are an amazingly diverse group of mammals (Image: Paul Bates)
A sharp rise in global temperatures about 50 million years ago may have been responsible for the evolution of bats, Science magazine reports.

This warming is linked to an explosion in the diversity of other mammals, but little was known about bat evolution.

New DNA data traces the origin of four major bat lineages to a brief period in the Eocene Epoch when the average global temperature rose by about 7C.

Bats make up 20% of mammals, yet their evolutionary history is poorly known.

The scientists, led by Emma Teeling from University College Dublin, Ireland, estimate that around 60% of the bat fossil record is missing.

Writing in Science, the international team of researchers propose that bats originated in the ancient landmass of Laurasia, possibly in an area now located in North America.

Insect prey

The gene sequencing data suggests bats split away on their own evolutionary path about 52-50 million years ago, at a time when the Earth experienced an event known as the Palaeocene-Eocene Thermal Maximum.

The warmer climate caused insects to flourish, and bats evolved unique aviation skills and echolocation to catch them, it is claimed.

The results therefore support the theory that the group known as the megabats are nested among the four major microbat lineages which originated in the early Eocene.

The Greater False vampire bat Megaderma lyra, photographed in India     Image: Paul Bates
The animals make up about 20% of all mammals (Image: Paul Bates)
They compared the DNA of modern bat families to reconstruct evolutionary relationships between microbats, which use echolocation, and megabats, which do not.

Megabats emerged later from these original bats.

"We suggest that... microbats diversified in response to an increase in prey diversity and that the varied microbat echolocation and flight strategies may have resulted from differential niche exploitation at that time," the researchers write in Science.

In an accompanying paper, Nancy Simmons from the American Museum of Natural History in New York, US, said: "As flying predators, capable of capturing prey on the wing, they would have had few competitors for the rich resources of the Eocene night."

Ancestors linking bats to other mammal groups lived during the Palaeocene period which followed the extinction of the dinosaurs. However, none of their fossils have ever been discovered.

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