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Newly described tree species from Tanzania is likely endangered

  • Researchers have described a new species of tree from the Usambara mountains of northeastern Tanzania.
  • The tree, which grows up to 20 meters (66 feet) in height, has been named Mischogyne iddii after Iddi Rajabu, a resident botanist at the Amani Nature Reserve, where some individuals of the tree can be found.
  • The newly described species is known from only two locations in the Usambara mountains, and the researchers estimate that fewer than 50 individuals remain, suggesting a threat category of endangered on the IUCN Red List for the species.

From the Usambara mountains of northeastern Tanzania, researchers have described a new species of tree that could already be on its way toward extinction.

The tree, which grows up to 20 meters (66 feet) in height and bears white flowers, would be hard to miss if encountered. But the species seems be incredibly rare. It is known from only two locations within the Eastern Arc Mountains, one in the Amani Nature Reserve in the Eastern Usambara Mountains and one in a private reserve in western Usambara, according to a new study.

Researchers have named it Mischogyne iddii, after Iddi Rajabu, a resident botanist at the Amani Nature Reserve and also co-author of the Trees of Amani Nature Reserve field guide.

The study’s lead author, Andrew Marshall, a conservation scientist at the University of York, U.K., told BBC Radio 4 that the aim of his research isn’t to find new species. “We’re trying to understand how forests work, how they recover when damaged,” he said. “Because these places have so many species, new ones tend to come up from time to time.”

The newly described species belongs to the custard apple family of trees, or Annonaceae, which, Marshall said, tend to all look very similar. In the case of M. iddii, the researchers were able to collect fruits and flowers from a low-hanging branch, which co-author George Gosline, a botanist at Kew Gardens, U.K., used to identify the undescribed tree as a new species.

“The discovery of this extremely rare species reaffirms the importance of the Eastern Arc Mountains as one of the most important reservoirs of biodiversity in Africa,” Gosline said in a statement. “The area is a refuge for ancient species from a time when a great forest covered all of tropical Africa. These forest remnants are precious and irreplaceable.”

The survival of M. iddii, however, is at risk. The two reserves where the species is known from are “‘islands’ within a deforested landscape with extensive clearance of forest in neighbouring areas,” the researchers write. Native trees are also under threat from invasive tree species like the umbrella tree (Maesopsis eminii), they add, which have taken over large parts of the Usambara forests.

Marshall and his colleagues say the new species likely has a very small population. This is because only seven M. iddii trees have been observed despite the Usambaras being studied for decades. The researchers estimate that fewer than 50 individuals remain, and suggest a threat category of endangered on the IUCN Red List for the species.

“The tree is in a particularly beautiful part of the world — up high in the clouded mountains and surrounded by tea estates. Now that we know it exists, we have to look at ways to protect it,” Marshall said. “With such a small population, it is important that it does not become isolated from other forests in the region, due to increasing agriculture. Small forests need to be connected to others to ensure seed dispersal and species adaptation to climate change.”

M. iddii grows up to 20 meters (66 feet) in height and bears white flowers. Image by Andrew Marshall.

Citation:

Gosline, G., Marshall, A. R., & Larridon, I. (2019). Revision and new species of the African genus Mischogyne (Annonaceae). Kew Bulletin74(28). doi:10.1007/s12225-019-9804-7