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takyon writes:

How much space do you need to evolve a new mammal? These worm-eating mice have the answer

To discover the lower limit, the team turned to islands, whose isolated locations often make for an ideal laboratory—researchers can usually determine which animals arrived there and which evolved there. Lawrence Heaney, an evolutionary biogeographer at The Field Museum of Natural History in Chicago, Illinois, worked for years cataloging mammal diversity on the Philippines's largest island, Luzon. He discovered that its 105,000 square kilometers hosted 66 mammal species, not including bats. Surely smaller islands could also allow new species to diversify, he thought. So he and his colleagues searched for just such a place. They settled on Mindoro, the seventh-largest island in the Philippines.

In 2013, they started an inventory of all the mammals there, including rats, mice, and the dwarf water buffalo. They set up live traps on the slopes of all five of Mindoro's mountain ranges to catch the smaller ones, including a kind of long-snouted, earthworm-eating mouse native to the island, on which they focused their initial analysis. After comparing their DNA and looks, the scientists realized the mice represented four separate species—three living on their own mountains, and one occupying the lowlands below.

Furthermore, the genetic analysis suggests that the four species evolved from a single ancestor that landed on Mindoro about 2.8 million years ago. That means the island is the smallest place ever documented to have evolved new mammals [DOI: 10.1111/jbi.13352] [DX] from a single ancestor, Heaney and his colleagues report today in the Journal of Biogeography.

Also at The Field Museum.

Original Submission