Future of Madagascar’s large-seeded plants in doubt without lemurs

For immediate release ‐ April 15, 2016

Contact: Jon Pishney, 919.707.8083. Images available upon request

Animal extinctions can often have complex effects on the overall structure of forest ecosystems. Using modern genetic tools and museum specimens from both living and fossil species, a team led by researchers at Yale University, the North Carolina Museum of Natural Sciences, Duke University, Pennsylvania State University, the New York Botanical Garden, and Hunter College have found that the extinction of several species of large lemurs in Madagascar has created isolated “orphaned” plant species that once depended upon the animals to eat and disperse their large seeds.

These large-seeded plant species face an uncertain future without lemurs capable of eating and dispersing their seeds, according to Yale’s Sarah Federman, a PhD candidate in the Department of Ecology and Evolutionary Biology and lead author of the study published the week of April 11 in the Proceedings of the National Academy of Sciences.

“We need to understand the impacts of past extinction events or we cannot adequately design conservation plans for the future,’’ Federman said.

An estimated 17 species of large lemur have gone extinct in the last few thousand years, and many of them are thought to have been important seed dispersers. Researchers examined characteristics of extinct and living lemur species to estimate the dispersal ability lost with these extinctions, and predict impact on the island’s flora. In the absence of now extinct lemurs, plant species with large seeds became “orphaned” or reliant upon poor dispersal substitutes such as wind, gravity, or rodents. Species identified as species of concern in this study together often comprise over a third of the trees present in any area of the island’s rainforests.

Alex Dornburg, Research Curator of Ichthyology at the North Carolina Museum of Natural Sciences and coauthor of the study said, “Our study really highlights the critical role that lemurs played in facilitating gene flow in rainforest trees, adding a new perspective to Madagascar’s conservation needs.” Without lemurs moving seeds around the landscape, plants are forced to breed with closely related individuals. This cycle of inbreeding increases the chances for rare genetic disorders or reduced immunity to pathogens and insect pests. “We have a bias towards thinking about plants as sustaining ecosystem health, but in many cases plants have evolved to be equally dependent on animals,” Dornburg added.

The team also identified contemporary examples of the precarious balance between lemurs and plants in Madagascar. For instance, the critically endangered black-and-white ruffed lemur is the last remaining species large enough to eat and disperse seeds of Canarium species. These plant species, which form a core component of the rainforest canopy, might eventually be lost if this lemur species goes extinct.

Primary funding for the study came from the National Science Foundation.

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