Mt Halcon forest mouse

The mouse Apomys gracilirostris is one of four closely related species on Mindoro Island in the Philippines. Credit: L. R. Heaney/The Field Museum

Evolution

Worm-eating mountain mice showcase evolution in action

One species has diverged into several, despite island’s small size.

A tropical island populated by worm-eating mice is the smallest such enclave yet known where one mammal has evolved into several species.

Speciation is thought to require a large amount of space to allow animals to separate and diversify in their own niches. To test how small this space can be, Lawrence Heaney at the Field Museum of Natural History in Chicago, Illinois, and his colleagues collected tissue samples from 21 mice living on the 9,735-square-kilometre Mindoro Island in the Philippines.

When the researchers sequenced the animals’ DNA, they found that the mice belonged to four different species of the genus Apomys. Each species lives on a different mountain, and all are descended from a single common ancestor that immigrated to Mindoro 1.5 million to 2.4 million years ago.

The finding could have implications for the design of protected areas for wildlife, the researchers say.