Scientists comparing the genes of five teeny lemur species found that, once upon a time, the animals’ disparate habitats were all connected. They published their findings in the Proceedings of the National Academy of Sciences.

All 24 species of mouse lemurs (genus Microcebus) are primates descended from a common ancestor in the forests of Madagascar more than 10 million years ago. In the intervening time, the species have scattered across the island. They still look a lot alike from the outside, but each species has adapted to its own environment—changes that left a mark in the lemurs’ genes.

Adorable, hardy, fast-breeding, and unique to their environment, mouse lemurs are a geneticist’s dream subject. Female mouse lemurs reach sexual maturity when they’re just 12 months old. This means that their generations are short; or, to put it another way, they evolve much more rapidly than many other mammals.

Paper co-author Steve Goodman of The Field Museum in Chicago has spent the last 30 years studying Madagascar’s wildlife. He and his colleagues are working to piece together the natural history of the island itself by studying the animals that live there. For this study, they compared the genetic codes of five different mouse lemur species. (One of those species, Microcebus lehilahytsara has special significance for Goodman: “lehilahytsara” is Malagasy for “good man.” In English, the species is called Goodman’s mouse lemur, for the biologist’s many scientific contributions on the island.)


Goodman's mouse lemur. Image Credit: © Robert Zingg, Zoo Zurich

 
Analysis of the lemurs’ DNA showed that the species were still genetically close to one another. “That suggests that their ancestors were able to disperse across forested habitat that no longer exists,” Goodman said. He and his colleagues believe the now-separate east and west sides of the island were likely linked by a patchwork of forests.

Looking back in time through changes in the lemurs' DNA, the researchers could identify when the species split from one another and, consequently, what might have been happening on the island to make that possible.

A longstanding theory of the island's biogeography holds that it was the arrival of humans thousands of years ago that triggered the ecological shift. Yet the lemurs' DNA showed that the species had clearly diverged long before then, indicating that the landscape was already on the move by the time we arrived. It seems that natural climate change had a hand in the slow geographic shift.

“Madagascar is one of the top conservation priorities in the world,” Goodman said. “All of the native land mammals on Madagascar occur nowhere else in the world. This study is important because it sheds light upon the long-term life history of Madagascar, before human colonization. It helps us understand change.”

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