Fossils reveal single tree species dominated Ethiopia rainforest

DALLAS (SMU) – A new study has found fossilized evidence that a rainforest growing around a volcanic lake in Ethiopia’s Mush Valley 21.73 million years ago was dominated by a single species of tree.

The dominant tree species belonged within the legume family, which includes  beans, peas, and giant trees in tropical forests.

“We have estimated the lake beds that contain the fossils were present for about 50,000 to 60,000 years,” said Bonnie Jacobs, an emeritus professor and paleobotanist at SMU (Southern Methodist University) and a co-author in the new study.

Tropical rain forests are famous for hosting a tremendous diversity of plants and animals. But occasionally rainforests become monodominant - dominated by just one tree species, Jacobs explained.

“It’s a phenomenon that happens today more often in Africa than elsewhere in the tropics, but it is still not common,” she said.  

Jacobs has spent a significant portion of her career conducting research in eastern Africa, including the Mush Valley, located about 160 kilometers northeast of the Ethiopian capital of Addis Ababa. The fossil record of the Mush Valley preserves plants and animals from a time soon after a land connection was established between Afro-Arabia and Eurasia – a land connection that marked the end of Africa’s island status.

Jacobs and other researchers published their findings in the journal PLOS ONE. The lead author of the study is Aaron Pan, the Executive Director of the Museum of Texas Tech University and a research associate at the Botanical Research Institute at the Fort Worth Botanic Garden.

Pan received his PhD in geology, with an emphasis in paleobotany, from SMU, where he also worked as a postdoctoral researcher. 

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